Retrovir

Retrovir

zidovudine

Manufacturer:

GlaxoSmithKline

Distributor:

Zuellig
/
Agencia Lei Va Hong
Full Prescribing Info
Contents
Zidovudine.
Description
Capsule: Each capsule contains 250 mg zidovudine.
Oral solution: Each ml of solution contains 10 mg zidovudine. The pack contains an oral-dosing syringe which should be fitted to the bottle before use.
IV infusion: Vials containing zidovudine 200 mg in 20ml solution (10 mg zidovudine/ml).
Excipients/Inactive Ingredients: Capsule: Capsule core: Maize starch, Microcrystalline Cellulose, Sodium Starch Glycollate, Magnesium Stearate.
Capsule coating: Titanium dioxide, Indigo carmine E132, Gelatin.
Printing ink: Black Iron Oxide E172.
Oral solution: Hydrogenated glucose syrup, glycerol, anhydrous citric acid, sodium benzoate, saccharin sodium, strawberry flavour, white sugar flavour and purified water.
IV infusion: Hydrochloric acid, Sodium hydroxide, Water for injection.
Action
Pharmacotherapeutic group: nucleoside analogue. ATC code: J05A F01.
Pharmacology: Pharmacodynamics: Mode of action: Zidovudine is an antiviral agent which is highly active in vitro against retroviruses including the Human Immunodeficiency Virus (HIV).
Zidovudine is phosphorylated in both infected and uninfected cells to the monophosphate (MP) derivative by cellular thymidine kinase. Subsequent phosphorylation of zidovudine-MP to the diphosphate (DP), and then the triphosphate (TP) derivative is catalysed by cellular thymidylate kinase and non-specific kinases respectively. Zidovudine-TP acts as an inhibitor of and substrate for the viral reverse transcriptase. The formation of further proviral DNA is blocked by incorporation of zidovudine-MP into the chain and subsequent chain termination. Competition by zidovudine-TP for HIV reverse transcriptase is approximately 100-fold greater than for cellular DNA polymerase alpha.
Clinical virology: The relationships between in vitro susceptibility of HIV to zidovudine and clinical response to therapy remain under investigation. In vitro sensitivity testing has not been standardised and results may therefore vary according to methodological factors. Reduced in vitro sensitivity to zidovudine has been reported for HIV isolates from patients who have received prolonged courses of Retrovir therapy. The available information indicates that for early HIV disease, the frequency and degree of reduction of in vitro sensitivity is notably less than for advanced disease.
The reduction of sensitivity with the emergence of zidovudine resistant strains limits the usefulness of zidovudine monotherapy clinically. In clinical studies, clinical end-point data indicate that zidovudine, particularly in combination with lamivudine, and also with didanosine or zalcitabine results in a significant reduction in the risk of disease progression and mortality. The use of a protease inhibitor in a combination of zidovudine and lamivudine, has been shown to confer additional benefit in delaying disease progression, and improving survival compared to the double combination on its own.
The anti-viral effectiveness in vitro of combinations of anti-retroviral agents are being investigated. Clinical and in vitro studies of zidovudine in combination with lamivudine indicate that zidovudine-resistant virus isolates can become zidovudine sensitive when they simultaneously acquire resistance to lamivudine. Furthermore there is clinical evidence that zidovudine plus lamivudine delays the emergence of zidovudine resistance in anti-retroviral naive patients.
No antagonistic effects in vitro were seen with zidovudine and other antiretrovirals (tested agents: abacavir, didanosine, lamivudine and interferon-alpha).
Resistance to thymidine analogues (of which zidovudine is one) is well characterised and is conferred by the stepwise accumulation of up to six specific mutations in the HIV reverse transcriptase at codons 41, 67, 70, 210, 215 and 219. Viruses acquire phenotypic resistance to thymidine analogues through the combination of mutations at codons 41 and 215 or by the accumulation of at least four of the six mutations. These thymidine analogue mutations alone do not cause high-level cross-resistance to any of the other nucleosides, allowing for the subsequent use of any of the other approved reverse transcriptase inhibitors.
Two patterns of multi-drug resistance mutations, the first characterised by mutations in the HIV reverse transcriptase at codons 62, 75, 77, 116 and 151 and the second involving a T69S mutation plus a 6-base pair insert at the same position, result in phenotypic resistance to AZT as well as to the other approved nucleoside reverse transcriptase inhibitors. Either of these two patterns of multinucleoside resistance mutations severely limits future therapeutic options.
In the US ACTGO76 trial, Retrovir was shown to be effective in reducing the rate of maternal-foetal transmission of HIV-1 (23% infection rate for placebo versus 8% for zidovudine) when administered (100 mg five times a day) to HIV-positive pregnant women (from week 14-34 of pregnancy) and their newborn infants (2 mg/kg every 6 hours) until 6 weeks of age. In the shorter duration 1998 Thailand CDC study, use of oral Retrovir therapy only (300 mg twice daily), from week 36 of pregnancy until delivery, also reduced the rate of maternal-foetal transmission of HIV (19% infection rate for placebo versus 9% for zidovudine). These data, and data from a published study comparing zidovudine regimens to prevent maternal-foetal HIV transmission have shown that short maternal treatments (from week 36 of pregnancy) are less efficacious than longer maternal treatments (from week 14-34 of pregnancy) in the reduction of perinatal HIV transmission.
Pharmacokinetics: Adults: Absorption: Capsule/Oral solution: Zidovudine is well absorbed from the gut and, at all dose levels studied, the bioavailability was 60-70%. From a bioequivalence study, steady-state mean (CV%) C[ss]max, C[ss]min, and AUC[ss] values in 16 patients receiving zidovudine 300 mg tablets twice daily were 8.57 (54%) microM (2.29 μg/ml), 0.08 (96%) microM (0.02 μg/ml), and 8.39 (40%) h*microM (2.24 h*μg/ml), respectively.
IV infusion: Dose-independent kinetics were observed in patients receiving one-hour infusions of 1 to 5 mg/kg 3 to 6 times daily. Mean steady state peak (Cssmax) and trough (Cssmin) plasma concentrations in adults following a one-hour infusion of 2.5 mg/kg every 4 hours were 4.0 and 0.4 μM, respectively (or 1.1 and 0.1 μg/ml).
Distribution: From studies with intravenous Retrovir, the mean terminal plasma half-life was 1.1 hours, the mean total body clearance was 27.1 ml/min/kg and the apparent volume of distribution was 1.6 Litres/kg.
In adults, the average cerebrospinal fluid/plasma zidovudine concentration ratio 2 to 4 hours after chronic intermittent oral dosing was found to be approximately 0.5. Data indicate that zidovudine crosses the placenta and is found in amniotic fluid and foetal blood. Zidovudine has also been detected in semen and milk.
Plasma protein binding is relatively low (34 to 38%) and drug interactions involving binding site displacement are not anticipated.
Biotransformation: Zidovudine is primarily eliminated by hepatic conjugation to an inactive glucuronidated metabolite. The 5'-glucuronide of zidovudine is the major metabolite in both plasma and urine, accounting for approximately 50-80% of the administered dose eliminated by renal excretion. 3'-amino-3'-deoxythymidine (AMT) has been identified as a metabolite of zidovudine following intravenous dosing.
Elimination: Renal clearance of zidovudine greatly exceeds creatinine clearance, indicating that significant tubular secretion takes place.
Paediatrics: Absorption: In children over the age of 5-6 months, the pharmacokinetic profile of zidovudine is similar to that in adults.
Capsule/Oral solution: Zidovudine is well absorbed from the gut and, at all dose levels studied, its bioavailability was 60-74% with a mean of 65%. Cssmax levels were 4.45 μM (1.19 μg/ml) following a dose of 120 mg Retrovir (in solution)/m2 body surface area and 7.7 μM (2.06 μg/ml) at 180 mg/m2 body surface area. Dosages of 180 mg/m2 four times daily in children produced similar systemic exposure (24 hour AUC 40.0 hr μM or 10.7 hr μg/ml) as doses of 200 mg six times daily in adults (40.7 hr μM or 10.9 hr μg/ml).
IV infusion: Cssmax levels were 1.46 μg/ml following an intravenous dose of 80 mg zidovudine/m2 body surface area, 2.26 μg/ml following 120 mg/m2 and 2.96 μg/ml following 160 mg/m2.
Distribution: With intravenous dosing, the mean terminal plasma half-life and total body clearance were 1.5 hours and 30.9 ml/min/kg respectively.
In children the mean cerebrospinal fluid/plasma zidovudine concentration ratio ranged from 0.52-0.85, as determined during oral therapy 0.5 to 4 hours after dosing and was 0.87 as determined during intravenous therapy 1-5 hours after a 1 hour infusion. During continuous intravenous infusion, the mean steady-state cerebrospinal fluid/plasma concentration ratio was 0.24.
Biotransformation: The major metabolite is 5'-glucuronide. After intravenous dosing, 29% of the dose was recovered unchanged in the urine and 45% excreted as the glucuronide.
Elimination: Renal clearance of zidovudine greatly exceeds creatinine clearance indicating that significant tubular secretion takes place.
The data available on the pharmacokinetics in neonates and young infants indicate that glucuronidation of zidovudine is reduced with a consequent increase in bioavailability, reduction in clearance and longer half-life in infants less than 14 days old but thereafter the pharmacokinetics appear similar to those reported in adults.
Pregnancy: The pharmacokinetics of zidovudine has been investigated in a study of eight women during the third trimester of pregnancy. As pregnancy progressed, there was no evidence of drug accumulation. The pharmacokinetics of zidovudine was similar to that of non-pregnant adults. Consistent with passive transmission of the drug across the placenta, zidovudine concentrations in infant plasma at birth were essentially equal to those in maternal plasma at delivery.
Elderly: No specific data are available on the pharmacokinetics of zidovudine in the elderly.
Renal impairment: Haemodialysis and peritoneal dialysis have no significant effect on zidovudine elimination whereas elimination of the inactive glucuronide metabolite is increased (see Dosage & Administration).
Capsule/Oral solution: In patients with severe renal impairment, apparent zidovudine clearance after oral zidovudine administration was approximately 50% of that reported in healthy subjects with normal renal function.
IV infusion: Compared to healthy subjects, patients with advanced renal failure have a 50% higher peak plasma concentration after oral administration. Systemic exposure (measured as area under the zidovudine concentration time curve) is increased 100%; the half-life is not significantly altered. In renal failure there is substantial accumulation of the major glucuronide metabolite but this does not appear to cause toxicity.
Hepatic impairment: There are limited data concerning the pharmacokinetics of zidovudine in patients with hepatic impairment (see Dosage & Administration).
Toxicology: Preclinical safety data: Mutagenicity: No evidence of mutagenicity was observed in the Ames test. However, zidovudine was weakly mutagenic in a mouse lymphoma cell assay and was positive in an in vitro cell transformation assay. Clastogenic effects (chromosome damage) were observed in an in vitro study in human lymphocytes and in in vivo oral repeat dose micronucleus studies in rats and mice. An in vivo cytogenetic study in rats did not show chromosomal damage. A study of the peripheral blood lymphocytes of eleven AIDS patients showed a higher chromosome breakage frequency in those who had received Retrovir than in those who had not. A pilot study has demonstrated that zidovudine is incorporated into leukocyte nuclear DNA of adults, including pregnant women, taking zidovudine as treatment for HIV-1 infection, or for the prevention of mother to child viral transmission. Zidovudine was also incorporated into DNA from cord blood leukocytes of infants from zidovudine-treated mothers. A transplacental genotoxicity study conducted in monkeys compared zidovudine alone with the combination of zidovudine and lamivudine at human-equivalent exposures. The study demonstrated that foetuses exposed in utero to the combination sustained a higher level of nucleoside analogue-DNA incorporation into multiple foetal organs, and showed evidence of more telomere shortening than in those exposed to zidovudine alone. The clinical significance of these findings is unknown.
Carcinogenicity: In oral carcinogenicity studies with zidovudine in mice and rats, late appearing vaginal epithelial tumours were observed. A subsequent intravaginal carcinogenicity study confirmed the hypothesis that the vaginal tumours were the result of long term local exposure of the rodent vaginal epithelium to high concentrations of unmetabolised zidovudine in urine. There were no other drug-related tumours observed in either sex of either species.
In addition, two transplacental carcinogenicity studies have been conducted in mice. One study, by the US National Cancer Institute, administered zidovudine at maximum tolerated doses to pregnant mice from day 12 to 18 of gestation. One year post-natally, there was an increase in the incidence of tumours in the lung, liver and female reproductive tract of offspring exposed to the highest dose level (420 mg/kg term body weight).
In a second study, mice were administered zidovudine at doses up to 40 mg/kg for 24 months, with exposure beginning prenatally on gestation day 10. Treatment related findings were limited to late-occurring vaginal epithelial tumours, which were seen with a similar incidence and time of onset as in the standard oral carcinogenicity study. The second study thus provided no evidence that zidovudine acts as a transplacental carcinogen.
It is concluded that the transplacental carcinogenicity data from the first study represents a hypothetical risk, whereas the reduction in risk of maternal transfection of HIV to the uninfected child by the use of zidovudine in pregnancy has been well proven.
Reproductive Toxicity: Studies in pregnant rats and rabbits given zidovudine orally at dosage levels up to 450 and 500 mg/kg/day respectively during the major period of organogenesis have revealed no evidence of teratogenicity. There was, however, a statistically significant increase in foetal resorptions in rats given 150 to 450 mg/kg/day and in rabbits given 500 mg/kg/day.
A separate study, reported subsequently, found that rats given a dosage of 3000 mg/kg/day, which is very near the oral median lethal dose (3683 mg/kg), caused marked maternal toxicity and an increase in the incidence of foetal malformations. No evidence of teratogenicity was observed in this study at the lower dosages tested (600 mg/kg/day or less).
Indications/Uses
Retrovir chemoprophylaxis is indicated for use in HIV-positive pregnant women (over 14 weeks of gestation) for prevention of maternal-foetal HIV transmission and for primary prophylaxis of HIV infection in newborn infants.
Capsule/Oral solution: Retrovir oral formulations are indicated in anti-retroviral combination therapy for Human Immunodeficiency Virus (HIV) infected adults and children.
IV infusion: Retrovir IV for Infusion is indicated for the short-term management of serious manifestations of Human Immunodeficiency Virus (HIV) infection in patients with Acquired Immune Deficiency Syndrome (AIDS) who are unable to take Retrovir oral formulations. If at all possible Retrovir IV should not be used as monotherapy for this indication (see Pharmacology: Pharmacodynamics under Actions).
Retrovir IV should only be used when oral treatment is not possible (except during labour and delivery - see Dosage & Administration).
Dosage/Direction for Use
Retrovir should be prescribed by physicians who are experienced in the treatment of HIV infection.
Dosage in the prevention of maternal-foetal transmission: Pregnant women (over 14 weeks of gestation) should be given 500 mg/day orally (100 mg five times per day) until the beginning of labour. During labour and delivery Retrovir should be administered intravenously at 2 mg/kg bodyweight given over one hour followed by a continuous intravenous infusion at 1 mg/kg/h until the umbilical cord is clamped.
Neonates should be given 0.2 mL/kg (2 mg/kg) bodyweight orally every 6 hours starting within 12 hours after birth and continuing until 6 weeks-old.
Care should be taken when calculating doses for neonates due to the small volumes of oral solution required. To facilitate dosing precision, an appropriately sized syringe with 0.1 mL graduation should be used to ensure accurate oral dosing of neonates (see oral solution product information).
Infants unable to receive oral dosing should be given Retrovir intravenously at 1.5 mg/kg bodyweight infused over 30 minutes every 6 hours.
In case of planned caesarean, the infusion should be started 4 hours before the operation. In the event of a false labour, the Retrovir infusion should be stopped and oral dosing restarted.
Dosage adjustments in patients with haematological adverse reactions: Substitution of zidovudine should be considered in patients whose haemoglobin level or neutrophil count fall to clinically significant levels. Other potential causes of anaemia or neutropenia should be excluded. Retrovir dose reduction or interruption should be considered in the absence of alternative treatments (see Contraindications and Precautions).
Dosage in the elderly: Zidovudine pharmacokinetics have not been studied in patients over 65 years of age and no specific data are available. However, since special care is advised in this age group due to age-associated changes such as the decrease in renal function and alterations in haematological parameters, appropriate monitoring of patients before and during use of Retrovir is advised.
Dosage in renal impairment: In patients with severe renal impairment, the recommended IV dosage is 1 mg/kg 3-4 times daily. This is equivalent to the current recommended oral daily dosage for this patient group of 300-400 mg allowing for oral bioavailability of 60-70%. Haematological parameters and clinical response may influence the need for subsequent dosage adjustment. For patients with end-stage renal disease maintained on haemodialysis or peritoneal dialysis, the recommended dose is 100 mg every 6-8 hrs (300 mg-400 mg daily) (see Pharmacology: Pharmacokinetics under Actions).
Dosage in hepatic impairment: Data in patients with cirrhosis suggest that accumulation of zidovudine may occur in patients with hepatic impairment because of decreased glucuronidation. Dosage reductions may be necessary but, due to the large variability in zidovudine exposures in patients with moderate to severe liver disease, precise recommendations cannot be made. If monitoring of plasma zidovudine levels is not feasible, physicians will need to monitor for signs of intolerance, such as the development of haematological adverse reactions (anaemia, leucopenia, neutropenia) and reduce the dose and/or increase the interval between doses as appropriate (see Precautions).
Capsule: Dosage in adults and adolescents weighing at least 30 kg: The usual recommended dose of Retrovir in combination with other anti-retroviral agents is 250 or 300 mg twice daily.
Dosage in children: Retrovir 100 mg capsules and Retrovir 100 mg/10 ml oral solution are available for use in children. (See table.)

Click on icon to see table/diagram/image

Oral solution is available for dosing children less than 8kg and for those children above 8kg unable to swallow capsules (see Oral Solution SPC).
Oral solution: Dosage in adults and adolescents weighing at least 30 kg: The usual recommended dose of Retrovir in combination with other antiretroviral agents is 250 or 300 mg twice daily.
Dosage in children: Retrovir 100 mg capsules are also available for use in children. Children weighing at least 9 kg and less than 30 kg: The recommended dose of Retrovir is 9 mg/kg twice daily in combination with other antiretroviral agents. The maximum dosage should not exceed 300 mg twice daily.
Children weighing at least 4 kg and less than 9 kg: The recommended dose of Retrovir is 12 mg/kg twice daily in combination with other antiretroviral agents.
Available data are insufficient to propose specific dosage recommendations for children weighing less than 4 kg (see previously mentioned maternal foetal transmission and Pharmacology: Pharmacokinetics under Actions).
IV infusion: The required dose of Retrovir IV for Infusion must be administered by slow intravenous infusion of the diluted product over a one-hour period.
Retrovir IV for Infusion must NOT be given intramuscularly.
Dilution: Retrovir IV for Infusion must be diluted prior to administration (see Special precautions for disposal and other handling under Cautions for Usage).
Dosage in adults: A dose for Retrovir IV for Infusion of 1 or 2 mg zidovudine/kg bodyweight every 4 hours provides similar exposure (AUC) to an oral dose of 1.5 or 3.0 mg zidovudine/kg every 4 hours (600 or 1200 mg/day for a 70 kg patient). The current recommended oral dose of Retrovir is 250 or 300 mg twice daily. This current dose is used as part of a multi-drug treatment regimen.
Patients should receive Retrovir IV for Infusion only until oral therapy can be administered.
Dosage in children: Limited data are available on the use of Retrovir IV for Infusion in children. A range of intravenous dosages between 80-160 mg/m2 every 6 hours (320-640 mg/m2/day) have been used. Exposure following the 120 mg/m2 dose every 6 hours approximately corresponds to an oral dose of 180 mg/m2 every 6 hours. An oral dose of Retrovir of 360 to 480 mg/m2 per day approximately corresponds to an intravenous dose of 240-320 mg/m2/day.
Overdosage
Symptoms and signs: No specific symptoms or signs have been identified following acute oral overdose with zidovudine, apart from those listed as undesirable effects such as fatigue, headache, vomiting, and occasional reports of haematological disturbances. Following a report where a patient took an unspecified quantity of zidovudine with serum levels consistent with an overdose of greater than 17 g there were no short term clinical, biochemical or haematological sequelae identified.
IV infusion: Dosages as high as 7.5 mg/kg by infusion every four hours for two weeks have been administered to five patients. One patient experienced an anxiety reaction while the other four had no untoward effects.
Treatment: Patients should be observed closely for evidence of toxicity (see Adverse Reactions) and given the necessary supportive therapy.
Haemodialysis and peritoneal dialysis appear to have a limited effect on elimination of zidovudine but enhances the elimination of the glucuronide metabolite.
Contraindications
Retrovir is contra-indicated in patients known to be hypersensitive to zidovudine, or to any of the excipients listed in Description.
Retrovir should not be given to patients with abnormally low neutrophil counts (less than 0.75 x 109/litre) or abnormally low haemoglobin levels (less than 7.5 g/decilitre or 4.65 mmol/litre).
Retrovir is contra-indicated in newborn infants with hyperbilirubinaemia requiring treatment other than phototherapy, or with increased transaminase levels of over five times the upper limit of normal.
Warnings
Lactic acidosis: lactic acidosis usually associated with hepatomegaly and hepatic steatosis has been reported with the use of zidovudine. Early symptoms (symptomatic hyperlactatemia) include benign digestive symptoms (nausea, vomiting and abdominal pain), non-specific malaise, loss of appetite, weight loss, respiratory symptoms (rapid and/or deep breathing) or neurological symptoms (including motor weakness).
Lactic acidosis has a high mortality and may be associated with pancreatitis, liver failure, or renal failure.
Lactic acidosis generally occurred after a few or several months of treatment.
Treatment with zidovudine should be discontinued in the setting of symptomatic hyperlactatemia and metabolic/lactic acidosis, progressive hepatomegaly, or rapidly elevating aminotransferase levels.
Caution should be exercised when administering zidovudine to any patient (particularly obese women) with hepatomegaly, hepatitis or other known risk factors for liver disease and hepatic steatosis (including certain medicinal products and alcohol). Patients co-infected with hepatitis C and treated with alpha interferon and ribavirin may constitute a special risk.
Patients at increased risk should be followed closely.
Special Precautions
While effective viral suppression with antiretroviral therapy has been proven to substantially reduce the risk of sexual transmission, a residual risk cannot be excluded. Precautions to prevent transmission should be taken in accordance with national guidelines.
Retrovir is not a cure for HIV infection or AIDS. Patients receiving Retrovir or any other antiretroviral therapy may continue to develop opportunistic infections and other complications of HIV infection.
The concomitant use of rifampicin or stavudine with zidovudine should be avoided (see Interactions).
Haematological Adverse Reactions: Anaemia (usually not observed before six weeks of Retrovir therapy but occasionally occurring earlier), neutropenia (usually not observed before four weeks' therapy but sometimes occurring earlier) and leucopenia (usually secondary to neutropenia) can be expected to occur in patients receiving Retrovir IV for Infusion; These occurred more frequently at high dosages (1200-1500 mg/day orally) and in patients with poor bone marrow reserve prior to treatment, particularly with advanced HIV disease (see Adverse Reactions).
Haematological parameters should be carefully monitored.
If the haemoglobin level falls to between 7.5 g/dl (4.65 mmol/l) and 9 g/dl (5.59 mmol/l) or the neutrophil count falls to between 0.75 x 109/l and 1.0 x 109/l, the daily dosage may be reduced until there is evidence of marrow recovery; alternatively, recovery may be enhanced by brief (2-4 weeks) interruption of Retrovir therapy. Marrow recovery is usually observed within 2 weeks after which time Retrovir therapy at a reduced dosage may be reinstituted. In patients with significant anaemia, dosage adjustments do not necessarily eliminate the need for transfusions (see Contraindications).
Liver disease: Zidovudine clearance in patients with mild hepatic impairment without cirrhosis [Child-Pugh scores of 5-6] is similar to that seen in healthy subjects, therefore no zidovudine dose adjustment is required. In patients with moderate to severe liver disease [Child-Pugh scores of 7-15], specific dosage recommendations cannot be made due to the large variability in zidovudine exposure observed, therefore zidovudine use in this group of patients is not recommended.
Patients with chronic hepatitis B or C and treated with combination antiretroviral therapy are at an increased risk of severe and potentially fatal hepatic adverse events. In case of concomitant antiviral therapy for hepatitis B or C, please also refer to the relevant product information for these medicinal products.
Patients with pre-existing liver dysfunction, including chronic active hepatitis, have an increased frequency of liver function abnormalities during combination antiretroviral therapy and should be monitored according to standard practice. If there is evidence of worsening liver disease in such patients, interruption or discontinuation of treatment must be considered (see Dosage & Administration).
Immune Reactivation Syndrome: In HIV-infected patients with severe immune deficiency at the time of institution of combination antiretroviral therapy (CART), an inflammatory reaction to asymptomatic or residual opportunistic pathogens may arise and cause serious clinical conditions, or aggravation of symptoms. Typically, such reactions have been observed within the first few weeks or months of initiation of CART. Relevant examples are cytomegalovirus retinitis, generalized and/or focal mycobacterial infections and Pneumocystis jirovecii pneumonia. Any inflammatory symptoms should be evaluated and treatment instituted when necessary. Autoimmune disorders (such as Graves' disease and autoimmune hepatitis) have also been reported to occur in the setting of immune reactivation; however, the reported time to onset is more variable and can occur many months after initiation of treatment.
Patients should be cautioned about the concomitant use of self-administered medications (see Interactions).
Osteonecrosis: Although the etiology is considered to be multifactorial (including corticosteroid use, alcohol consumption, severe immunosuppression, higher body mass index), cases of osteonecrosis have been reported particularly in patients with advanced HIV-disease and/or long-term exposure to combination antiretroviral therapy (CART). Patients should be advised to seek medical advice if they experience joint aches and pain, joint stiffness or difficulty in movement.
Patients co-infected with hepatitis C virus: The concomitant use of ribavirin with zidovudine is not recommended due to an increased risk of anaemia (see Interactions).
Capsule/Oral solution: Haematological Adverse Reactions: For patients with advanced symptomatic HIV disease it is generally recommended that blood tests are performed at least every two weeks for the first three months of therapy and at least monthly thereafter. Depending on the overall condition of the patient, blood tests may be performed less often, for example every 1 to 3 months.
Oral solution: Mitochondrial toxicity: Nucleoside and nucleotide analogues have been demonstrated in vitro and in vivo to cause a variable degree of mitochondrial damage. There have been reports of mitochondrial dysfunction in HIV-negative infants exposed in utero and/or post-natally to nucleoside analogues. The main adverse events reported are haematological disorders (anaemia, neutropenia), metabolic disorders (hyperlactataemia, hyperlipasaemia). These events are often transitory. Some late-onset neurological disorders have been reported (hypertonia, convulsion, abnormal behaviour). Whether the neurological disorders are transient or permanent is currently unknown. Any child exposed in utero to nucleoside and nucleotide analogues, even HIV-negative children, should have clinical and laboratory follow-up and should be fully investigated for possible mitochondrial dysfunction in case of relevant signs or symptoms. These findings do not affect current recommendations to use antiretroviral therapy in pregnant women to prevent vertical transmission of HIV.
Lipodystrophy: Combination antiretroviral therapy has been associated with the redistribution of body fat (lipodystrophy) in HIV patients. The long-term consequences of these events are currently unknown. Knowledge about the mechanism is incomplete. A connection between visceral lipomatosis and PIs and lipoatrophy and NRTIs has been hypothesised. A higher risk of lipodystrophy has been associated with individual factors such as older age, and with drug related factors such as longer duration of antiretroviral treatment and associated metabolic disturbances. Clinical examination should include evaluation for physical signs of fat redistribution. Consideration should be given to the measurement of fasting serum lipids and blood glucose. Lipid disorders should be managed as clinically appropriate (see Adverse Reactions).
Patients with rare hereditary problems of fructose intolerance should not take this medicine.
Capsule/IV infusion: Mitochondrial dysfunction following exposure in utero: Nucleoside and nucleotide analogues may impact mitochondrial function to a variable degree, which is most pronounced with stavudine, didanosine and zidovudine. There have been reports of mitochondrial dysfunction in HIV-negative infants exposed in utero and/or post-natally to nucleoside analogues; these have predominantly concerned treatment with regimens containing zidovudine. The main adverse reactions reported are haematological disorders (anaemia, neutropenia) and metabolic disorders (hyperlactatemia, hyperlipasaemia). These events have often been transitory. Late-onset neurological disorders have been reported rarely (hypertonia, convulsion, abnormal behaviour). Whether such neurological disorders are transient or permanent is currently unknown. These findings should be considered for any child exposed in utero to nucleoside and nucleotide analogues, who presents with severe clinical findings of unknown etiology, particularly neurologic findings. These findings do not affect current recommendations to use antiretroviral therapy in pregnant women to prevent vertical transmission of HIV.
Lipoatrophy: Treatment with zidovudine has been associated with loss of subcutaneous fat, which has been linked to mitochondrial toxicity. The incidence and severity of lipoatrophy are related to cumulative exposure. This fat loss, which is most evident in the face, limbs and buttocks, may not be reversible when switching to a zidovudine-free regimen. Patients should be regularly assessed for signs of lipoatrophy during therapy with zidovudine and zidovudine-containing products. Therapy should be switched to an alternative regimen if there is suspicion of lipoatrophy development.
Weight and metabolic parameters: An increase in weight and in levels of blood lipids and glucose may occur during antiretroviral therapy. Such changes may in part be linked to disease control and life style. For lipids, there is in some cases evidence for a treatment effect, while for weight gain there is no strong evidence relating this to any particular treatment. For monitoring of blood lipids and glucose reference is made to established HIV treatment guidelines. Lipid disorders should be managed as clinically appropriate.
Effects on ability to drive and use machines: There have been no studies to investigate the effect of Retrovir on driving performance or the ability to operate machinery. Furthermore, a detrimental effect on such activities cannot be predicted from the pharmacology of the drug. Nevertheless, the clinical status of the patient and the adverse reaction profile of Retrovir should be borne in mind when considering the patient's ability to drive or operate machinery.
Retrovir IV for Infusion is generally used in an in-patient hospital population and information on ability to drive and use machinery is not usually relevant.
IV infusion: Haematological Adverse Reactions: It is recommended that blood tests are performed at least weekly in patients receiving Retrovir IV for Infusion.
Data on the use of Retrovir for periods in excess of 2 weeks are limited.
Latex allergy: The rubber stopper of the Retrovir IV for Infusion vials contains dry natural latex rubber that has the potential to cause allergic reactions in latex sensitive individuals.
Use In Pregnancy & Lactation
Pregnancy: Oral solution: The use of Retrovir in pregnant women over 14 weeks of gestation, with subsequent treatment of their newborn infants, has been shown to significantly reduce the rate of maternal-foetal transmission of HIV based on viral cultures in infants.
The results from the pivotal U.S. placebo-controlled study indicated that Retrovir reduced maternal-foetal transmission by approximately 70%. In this study, pregnant women had CD4 cell counts of 200 to 1818/mm3 (median in treated group 560/mm3) and began treatment therapy between weeks 14 and 34 of gestation and had no clinical indications for Retrovir therapy; their newborn infants received Retrovir until 6-weeks old.
A decision to reduce the risk of maternal transmission of HIV should be based on the balance of potential benefits and potential risk. Pregnant women considering the use of Retrovir during pregnancy for prevention of HIV transmission to their infants should be advised that transmission may still occur in some cases despite therapy.
The efficacy of zidovudine to reduce the maternal-foetal transmission in women with previously prolonged treatment with zidovudine or other antiretroviral agents or women infected with HIV strains with reduced sensitivity to zidovudine is unknown.
It is unknown whether there are any long-term consequences of in utero and infant exposure to Retrovir.
Based on the animal carcinogenicity/mutagenicity findings a carcinogenic risk to humans cannot be excluded (see Pharmacology: Toxicology: Preclinical Safety Data under Actions). The relevance of these findings to both infected and uninfected infants exposed to Retrovir is unknown. However, pregnant women considering using Retrovir during pregnancy should be made aware of these findings.
A large amount of data on pregnant women (more than 3000 exposed outcomes) indicate no malformative nor feto/neonatal toxitcity. Retrovir can be used during pregnancy if clinically needed. Retrovir should only be used prior to the 14th week of gestation when the potential benefit to the mother and foetus outweigh the risks. Studies in pregnant rats and rabbits given zidovudine orally at dosage levels up to 450 and 500 mg/kg/day respectively during the major period of organogenesis have revealed no evidence of teratogenicity. There was, however, a statistically significant increase in foetal resorptions in rats given 150 to 450 mg/kg/day and in rabbits given 500 mg/kg/day.
A separate study, reported subsequently, found that rats given a dosage of 3000 mg/kg/day, which is very near the oral median lethal dose (3683 mg/kg), caused marked maternal toxicity and an increase in the incidence of foetal malformations. No evidence of teratogenicity was observed in this study at the lower dosages tested (600 mg/kg/day or less).
Capsule/IV infusion: As a general rule, when deciding to use antiretroviral agents for the treatment of HIV infection in pregnant women and consequently for reducing the risk of HIV vertical transmission to the newborn, the animal data (see Pharmacology: Toxicology: Preclinical safety data under Actions) as well as the clinical experience in pregnant women should be taken into account. In the present case, the use in pregnant women of zidovudine, with subsequent treatment of the newborn infants, has been shown to reduce the rate of maternal-foetal transmission of HIV.
A large amount of data on pregnant women (more than 3000 outcomes from first trimester and more than 3000 outcomes from second and third trimester exposure) indicate no malformative toxicity. Retrovir can be used during pregnancy if clinically needed. The malformative risk is unlikely in humans based on the mentioned large amount of data.
Zidovudine has been associated with reproductive toxicity findings in animal studies (see Pharmacology: Toxicology: Preclinical safety data under Actions). The active ingredients of Retrovir may inhibit cellular DNA replication and zidovudine has been shown to be a transplacental carcinogen in one animal study. The clinical relevance of these findings is unknown. Placental transfer of zidovudine has been shown to occur in humans.
Mitochondrial dysfunction: nucleoside and nucleotide analogues have been demonstrated in vitro and in vivo to cause a variable degree of mitochondrial damage. There have been reports of mitochondrial dysfunction in HIV-negative infants exposed in utero and/or post-natally to nucleoside analogues (see Precautions).
Fertility: Zidovudine did not impair male or female fertility in rats given oral doses of up to 450 mg/kg/day. There are no data on the effect of Retrovir on human female fertility. In men, Retrovir has not been shown to affect sperm count, morphology or motility.
Breast-feeding: After administration of a single dose of 200 mg zidovudine to HIV-infected women, the mean concentration of zidovudine was similar in human milk and serum. It is recommended that mothers infected by HIV do not breast-feed their infants under any circumstances in order to avoid transmission of HIV.
Adverse Reactions
The adverse reaction profile appears similar for adults and children. The most serious adverse reactions include anaemia (which may require transfusions), neutropenia and leucopenia. These occurred more frequently at higher dosages (1200-1500 mg/day) and in patients with advanced HIV disease (especially when there is poor bone marrow reserve prior to treatment), and particularly in patients with CD4 cell counts less than 100/mm3. Dosage reduction or cessation of therapy may become necessary (see Precautions).
The incidence of neutropenia was also increased in those patients whose neutrophil counts, haemoglobin levels and serum vitamin B12 levels were low at the start of Retrovir therapy. The following events have been reported in patients treated with Retrovir.
The adverse events considered at least possibly related to the treatment (adverse drug reactions, ADR) are listed as follows by body system, organ class and absolute frequency. Frequencies are defined as Very common (≥1/10), Common (≥1/100 to <1/10), Uncommon (≥1/1,000 to <1/100), Rare (≥1/10,000 to <1/1,000) and Very rare (<1/10,000).
Blood and lymphatic system disorders: Common: Anaemia, neutropenia and leucopenia.
Uncommon: Pancytopenia with bone marrow hypoplasia, thrombocytopenia.
Rare: Pure red cell aplasia.
Very rare: Aplastic anaemia.
Metabolism and nutrition disorders: Rare: Lactic acidosis in the absence of hypoxaemia, anorexia.
Psychiatric disorders: Rare: Anxiety and depression.
Nervous system disorders: Very common: Headache.
Common: Dizziness.
Rare: Convulsions, loss of mental acuity, insomnia, paraesthesia, somnolence.
Cardiac disorders: Rare: Cardiomyopathy.
Respiratory, thoracic and mediastinal disorders: Uncommon: Dyspnoea.
Rare: Cough.
Gastrointestinal disorders: Very common: Nausea.
Common: Vomiting, diarrhoea and abdominal pain.
Uncommon: Flatulence.
Rare: Oral mucosa pigmentation, taste disturbance and dyspepsia. Pancreatitis.
Hepatobiliary disorders: Common: Raised blood levels of liver enzymes and bilirubin.
Rare: Liver disorders such as severe hepatomegaly with steatosis.
Skin and subcutaneous tissue disorders: Uncommon: Rash and pruritis.
Rare: Urticaria, nail and skin pigmentation, and sweating.
Musculoskeletal and connective tissue disorders: Common: Myalgia.
Uncommon: Myopathy.
Renal and urinary disorders: Rare: Urinary frequency.
Reproductive system and breast disorders: Rare: Gynaecomastia.
General disorders and administration site disorders: Common: Malaise.
Uncommon: Asthenia, fever, and generalised pain.
Rare: Chest pain and influenza-like syndrome, chills.
The available data from studies of Retrovir Oral Formulations indicate that the incidence of nausea and other frequently reported clinical adverse reactions consistently decreased over time during the first few weeks of therapy with Retrovir.
Experience with Retrovir IV for Infusion treatment for periods in excess of two weeks is limited, although some patients have received treatment for up to 12 weeks. The most frequent adverse reactions were anaemia, neutropenia and leucopenia. Local reactions were infrequent.
Adverse reactions with Retrovir for the prevention of maternal-foetal transmission: In a placebo-controlled trial, overall clinical adverse reactions and laboratory test abnormalities were similar for women in the Retrovir and placebo groups. However, there was a trend for mild and moderate anaemia to be seen more commonly prior to delivery in the zidovudine treated women.
In the same trial, haemoglobin concentrations in infants exposed to Retrovir for this indication were marginally lower than in infants in the placebo group, but transfusion was not required. Anaemia resolved within 6 weeks after completion of Retrovir therapy. Other clinical adverse reactions and laboratory test abnormalities were similar in the Retrovir and placebo groups. It is unknown whether there are any long-term consequences of in utero and infant exposure to Retrovir.
Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.
Cases of lactic acidosis, sometimes fatal, usually associated with severe hepatomegaly and hepatic steatosis, have been reported with the use of zidovudine (see Precautions).
Treatment with zidovudine has been associated with loss of subcutaneous fat which is most evident in the face, limbs and buttocks. Patients receiving Retrovir should be frequently examined and questioned for signs of lipoatrophy. When such development is found, treatment with Retrovir should not be continued (see Precautions).
Weight and levels of blood lipids and glucose may increase during antiretroviral therapy (see Precautions).
In HIV-infected patients with severe immune deficiency at the time of initiation of combination antiretroviral therapy (CART), an inflammatory reaction to asymptomatic or residual opportunistic infections may arise (see Precautions).
Cases of osteonecrosis have been reported, particularly in patients with generally acknowledged risk factors, advanced HIV disease or long-term exposure to combination antiretroviral therapy (CART). The frequency of this is unknown (see Precautions).
IV infusion: Autoimmune disorders (such as Graves' disease and autoimmune hepatitis) have also been reported; however, the reported time to onset is more variable and these events can occur many months after initiation of treatment (see Precautions).
Reporting of suspected adverse reactions: Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product.
Drug Interactions
Limited data suggests that co-administration of zidovudine with rifampicin decreases the AUC (area under the plasma concentration curve) of zidovudine by 48% ± 34%. This may result in a partial loss or total loss of efficacy of zidovudine. The concomitant use of rifampicin with zidovudine should be avoided (see Precautions).
Zidovudine in combination with stavudine is antagonistic in vitro. The concomitant use of stavudine with zidovudine should be avoided (see Precautions).
Probenecid increases the AUC of zidovudine by 106% (range 100 to 170%). Patients receiving both drugs should be closely monitored for haematological toxicity.
A modest increase in Cmax (28%) was observed for zidovudine when administered with lamivudine, however overall exposure (AUC) was not significantly altered. Zidovudine has no effect on the pharmacokinetics of lamivudine.
Phenytoin blood levels have been reported to be low in some patients receiving Retrovir, while in one patient a high level was noted. These observations suggest that phenytoin levels should be carefully monitored in patients receiving both drugs.
Atovaquone: Zidovudine does not appear to affect the pharmacokinetics of atovaquone. However, pharmacokinetic data have shown that atovaquone appears to decrease the rate of metabolism of zidovudine to its glucuronide metabolite (steady state AUC of zidovudine was increased by 33% and peak plasma concentration of the glucuronide was decreased by 19%). At zidovudine dosages of 500 or 600 mg/day it would seem unlikely that a three week, concomitant course of atovaquone for the treatment of acute PCP would result in an increased incidence of adverse reactions attributable to higher plasma concentrations of zidovudine. Extra care should be taken in monitoring patients receiving prolonged atovaquone therapy.
Valproic acid, fluconazole or methadone when co-administered with zidovudine have been shown to increase the AUC with a corresponding decrease in its clearance. As only limited data are available the clinical significance of these findings is unclear but if zidovudine is used concurrently with either valproic acid, fluconazole or methadone, patients should be monitored closely for potential toxicity of zidovudine.
Exacerbation of anaemia due to ribavirin has been reported when zidovudine is part of the regimen used to treat HIV although the exact mechanism remains to be elucidated. The concomitant use of ribavirin with zidovudine is not recommended due to an increased risk of anaemia (see Precautions). Consideration should be given to replacing zidovudine in a combination ART regimen if this is already established. This would be particularly important in patients with a known history of zidovudine induced anaemia.
Concomitant treatment, especially acute therapy, with potentially nephrotoxic or myelosuppressive drugs (eg. systemic pentamidine, dapsone, pyrimethamine, co-trimoxazole, amphotericin, flucytosine, ganciclovir, interferon, vincristine, vinblastine and doxorubicin) may also increase the risk of adverse reactions to zidovudine. If concomitant therapy with any of these drugs is necessary then extra care should be taken in monitoring renal function and haematological parameters and, if required, the dosage of one or more agents should be reduced.
Limited data from clinical trials do not indicate a significantly increased risk of adverse reactions to zidovudine with cotrimoxazole, aerosolised pentamidine, pyrimethamine and aciclovir at doses used in prophylaxis.
Capsule/Oral solution: Clarithromycin tablets reduce the absorption of zidovudine. This can be avoided by separating the administration of zidovudine and clarithromycin by at least two hours.
Caution For Usage
Special precautions for disposal and other handling: Capsule/Oral solution: No special requirements for disposal.
IV infusion: Retrovir IV for Infusion must be diluted prior to administration. Since no antimicrobial preservative is included, dilution must be carried out under full aseptic conditions, preferably immediately prior to administration, and any unused portion of the vial should be discarded.
The required dose should be added to and mixed with Glucose Intravenous Infusion 5% w/v to give a final zidovudine concentration of either 2 mg/ml or 4 mg/ml. These dilutions are chemically and physically stable for up to 48 hours at both 5°C and 25°C. Should any visible turbidity appear in the product either before or after dilution or during infusion, the preparation should be discarded.
Incompatibilities: Capsule/Oral solution: Not applicable.
IV infusion: In the absence of compatibility studies, this medicinal product must not be mixed with other medicinal products.
Storage
Protect from light.
Capsule: Store in the original package.
MIMS Class
ATC Classification
J05AF01 - zidovudine ; Belongs to the class of nucleoside and nucleotide reverse transcriptase inhibitors. Used in the systemic treatment of viral infections.
Presentation/Packing
Cap 250 mg (hard gelatin capsules with opaque blue cap and opaque white body coded GSJV2) x 40's. Oral soln 10 mg/mL (clear, pale yellow, strawberry-flavoured) x 200 mL. IV infusion 10 mg/mL (clear, colourless to slightly yellow, sterile aqueous solution) x 20 mL x 5's.
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