Acute Hypersensitivity Reactions: In the event of severe acute hypersensitivity reactions, such as anaphylaxis, severe cutaneous adverse reactions (SCAR) [e.g., acute generalized exanthematous pustulosis, Stevens-Johnson Syndrome, toxic epidermal necrolysis, drug rash with eosinophilia and systemic symptoms (DRESS)], and Henoch-Schönlein purpura, clarithromycin treatment should be discontinued immediately and appropriate therapy be instituted.
Serious hypersensitivity reactions may require immediate emergency treatment including epinephrine, antihistamines or corticosteroids.
QT Prolongation: Clarithromycin has been associated with QT interval prolongation and infrequent cases of arrhythmia including torsades de pointes. Fatalities have been reported. Due to the risk of QT prolongation, clarithromycin should be avoided in patients with ongoing proarrhythmic conditions such as coronary artery disease, uncorrected hypokalemia or hypomagnesemia, clinically significant bradycardia, and in patients receiving class I (quinidine, procainamide) or class III (dofetilide, amiodarone, sotalol) antiarrhythmic agents. Elderly patients may be more susceptible to drug-associated effects on the QT interval.
Hepatotoxicity: Hepatic dysfunction, including increased liver enzymes, and hepatocellular and/or cholestatic hepatitis (with or without jaundice), has been reported with clarithromycin. The hepatic impairment may be severe and is usually reversible. In some cases, hepatic failure resulting in death has been reported and generally has been associated with serious underlying illnesses and/or concomitant medications.
Clarithromycin should be discontinued immediately if signs and symptoms of hepatitis occur, such as anorexia, jaundice, dark urine, pruritus, or tender abdomen.
Use of Clarithromycin with Other Drugs: Use of Clarithromycin with other drugs may lead to drug-drug interactions.
Atypical Antipsychotics (quetiapine): Due to inhibition of CYP3A by clarithromycin, concomitant use of clarithromycin with quetiapine results in increased quetiapine concentrations. Serious and life-threatening adverse reactions, including malignant neuroleptic syndrome, have been reported. Clarithromycin should not be used in combination with quetiapine unless clinically necessary (see Interactions). Monitoring and dose reductions may be required.
Oral Hypoglycemic Agents/Insulin: The concomitant use of clarithromycin and oral hypoglycemic agents (such as sulfonylureas) and/or insulin can result in significant hypoglycemia. Careful monitoring of glucose is recommended (see Interactions).
Oral Anticoagulants: There is a risk of serious hemorrhage and significant elevations in International Normalized Ratio (INR) and prothrombin time when clarithromycin is concomitantly used with warfarin. INR and prothrombin times should be frequently monitored while patients are receiving clarithromycin and oral anticoagulants concomitantly (see Interactions).
HMG-CoA Reductase Inhibitors: Concomitant use of clarithromycin with lovastatin or simvastatin is contraindicated (see Contraindications). Caution should be exercise when prescribing clarithromycin with other statins. Rhabdomyolysis has been reported in patients taking clarithromycin and statins. Patients should be monitored for signs and symptoms of myopathy. In situations where the concomitant use of clarithromycin with statins cannot be avoided, it is recommended to prescribe the lowest registered dose of the statin. Use of a statin that is not dependent on CYP3A metabolism (e.g., fluvastatin) can be considered (see Interactions).
Triazolobenzodiazepines and Related Benzodiazepines: Caution is advised regarding the concomitant administration of clarithromycin with triazolobenzodiazepines (such as triazolam and alprazolam), or with other benzodiazopenes (such as intravenous midazolam) due to increased risk of central nervous system (CNS) effects (e.g., somnolence and confusion) (see Interactions).
Calcium Channel Blockers: Caution is advised regarding the concomitant administration of clarithromycin and calcium channel blockers metabolized by CYP3A4 (e.g., verapamil, amlodipine, diltiazem, nifedipine) due to risk of hypotension and acute kidney injury. Most reports of acute kidney injury with calcium channel blockers metabolized by CYP3A4 involved elderly patients 65 years of age or older. Use clarithromycin with caution when administered concomitantly with medications that induce the cytochrome CYP3A4 enzyme (see Interactions).
Colchicine Toxicity: There have been post-marketing reports of colchicine toxicity with concomitant use of clarithromycin and colchicine, especially in the elderly, some of which occurred in patients with renal insufficiency. Deaths have been reported in some such patients (see Interactions).
All-Cause Mortality in Patients With Coronary Artery Disease 1 to 10 Years After Clarithromycin: In one clinical trial evaluating treatment with clarithromycin on outcomes in patients with coronary artery disease, an increase in risk of all-cause mortality one year or more after the end of treatment was observed in patients randomized to receive clarithromycin. Clarithromycin for treatment of coronary artery disease is not an approved indication. The cause of the increased risk has not been established. Other epidemiologic studies evaluating this risk have shown variable results. Consider balancing this potential risk with treatment benefits when prescribing clarithromycin in patients who have suspected or confirmed coronary artery disease.
Clostridium difficile-associated diarrhea (CDAD): This has been reported with the use of nearly all antibacterial agents, including clarithromycin, and may range in severity from mild diarrhea to fatal colitis. It is important to consider this diagnosis in patients who present with diarrhea following administration of antibacterial agents.
Myasthenia Gravis: Exacerbation of symptoms of myasthenia gravis and new onset of myasthenic syndrome has been reported in patients receiving clarithromycin.
Patients Infected with Human Immunodeficiency Virus (HIV): Several studies of HIV-positive patients receiving clarithromycin for treatment of MAC infection have shown poorer survival in those patients randomized to receive doses higher than 500 mg twice a day. The explanation for these results has not been determined. Treatment or prophylaxis of MAC infection with clarithromycin should not exceed the approved dose of 500 mg twice a day.
Skin and soft tissue infections of mild to moderate severity: These infections are most often caused by Staphylococcus aureus and Streptococcus pyogenes, both of which may be resistant to macrolides. Therefore, it is important that sensitivity testing be performed. In cases where beta-lactam antibiotics cannot be used (e.g., allergy), other antibiotics, such as clindamycin, may be the drug of first choice. Currently, macrolides are only considered to play a role in some skin and soft tissue infections, such as those caused by Corynebacterium minutissimum, acne vulgaris, and erysipelas and in situations where penicillin treatment cannot be used.
Pneumonia: In view of the emerging resistance of Streptococcus pneumoniae to macrolides, it is important that susceptibility testing be performed when prescribing clarithromycin for community-acquired pneumonia. In hospital-acquired pneumonia, clarithromycin should be used in combination with additional appropriate antibiotics.
Other Precautions: Use with caution in patients receiving other ototoxic drugs, especially aminoglycosides. Monitoring of vestibular and auditory function should be carried out during and after treatment.
There is a possibility of cross resistance between clarithromycin and other macrolides, as well as lincomycin and clindamycin.
For the eradication of Helicobacter pylori, clarithromycin and amoxicillin should not be administered to patients with renal impairment since the appropriate dosage in this patient population has not yet been established.
Clarithromycin in combination with ranitidine bismuth citrate should not be used in patients with creatinine clearance <25 mL/minute and in those with a history of acute porphyria.
Prescribing clarithromycin in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to be beneficial to the patient and increases the risk of the development of drug-resistant microorganisms.
As with other antibacterial drugs, long term or repeated use may result in overgrowth of non-susceptible organisms, including fungi. Use of any antimicrobial therapy, such as clarithromycin, to treat Helicobacter pylori infection may select for drug-resistant organisms.
Effects on the Ability to Drive and Use Machines: The potential for dizziness, vertigo, confusion and disorientation, which may occur with the medication, should be taken into account before patients drive or use machines.
Hepatic Impairment: Formation of 14-OH clarithromycin is reduced in patients with moderate to severe hepatic impairment. However, there is also increased renal clearance of the parent drug that dosage adjustment might not be necessary unless renal function is also impaired.
Renal Impairment: Clarithromycin's serum t1/2 is prolonged in patients with impaired renal function and dosage should be adjusted as necessary.
In general, clarithromycin may be used without dosage adjustment in patients with hepatic impairment and normal renal function. However, in patients with creatinine clearances <30 mL/min with or without hepatic impairment, dosage reduction or prolongation of dosing intervals for clarithromycin may be necessary.
Use in Children: The safety and efficacy of clarithromycin in pediatric patients under 6 months old have not been established. The safety of clarithromycin in children younger than 20 months old with Mycobacterium avium complex infection has not been established.
Use in Elderly: Peak serum concentrations and AUCs of clarithromycin and 14-OH clarithromycin may be increased in elderly patients 65 to 81 years old. This may be due to age-related decrease in renal function. However, increased incidence of adverse event reported in this age group has not been seen in clinical studies. Dosage modification may be required for elderly patients with severe renal impairment.
Elderly patients may be more susceptible to development of torsades de pointes arrhythmias that younger patients.
Use in Pregnancy: Clarithromycin has been associated with adverse effects of pregnancy outcome and/or embryo-fetal development in animals at doses that produced plasma levels 2 to 17 times those achieved with the maximum recommended human doses (see Use in Pregnancy & Lactation).