Each Film-Coated Tablet contains: Entecavir 500 mcg.
Entecavir is a white to off-white powder. It is slightly soluble in water (2.4 mg/mL), and the pH of the saturated solution in water is 7.9 at 25°±0.5°C.
Pharmacology: Pharmacodynamics: Mechanism of Action: HBV polymerase (reverse transcriptase, rt): (1) base priming, (2) reverse transcription of the negative strand from the pregenomic messenger rna, and (3) synthesis of the positive strand of HBV DNA. Upon activation by kinases, the drug can be incorporated into the DNA which has the ultimate effect of inhibiting the HBV polymerase activity.
Pharmacokinetics: Entecavir is absorbed from the gastrointestinal tract after oral doses. Peak plasma concentrations occur 30 to 90 minutes after a dose and steady state concentrations after 6 to 10 days of treatment. Bioavailability of the tablet formulation is equal to that of the oral solution and they may be given interchangeably. Binding of entecavir to plasma proteins is about 13% in vitro. Entecavir is not metabolized by the cytochrome P450 system. It is mainly eliminated by the kidneys by glomerular filtration and active tubular secretion, with a terminal elimination half-life of 128 to 149 hours. Minor amounts of glucuronide and sulfate conjugate metabolites occur. Entecavir is partially removed by haemodialysis.
Microbiology: Antiviral Action: Entecavir is phosphorylated intracellularly to the active triphospate form which competes with deoxyguanosine triphosphate, the natural substrate of hepatitis B virus reverse transcriptase, thereby inhibiting every stage of the enzyme's activity.
Treatment of chronic hepatitis B virus in adults with compensated liver disease with evidence of active viral replication, persistently elevated liver enzyme values, and histologically active disease including those resistant to lamivudine.
The usual dose of entecavir in nucleoside treatment-naive patients is 500 micrograms once daily, either with or without food. A dose of 1 mg once daily should be used in patients with a history of hepatitis B viraemia during lamivudine therapy or with known resistance to lamivudine. For details of reduced doses to be used in patients with renal impairment, see Administration of Renal Impairment as follows.
Administration in Renal Impairment: Doses of entecavir should be reduced in patients with renal impairment according to creatinine clearance (CC) as follows: CC 30 to 49 mL/minute: 250 micrograms once daily in nucleoside treatment-naive patients; 500 micrograms once daily in lamivudine-refractory patients.
CC 10 to 29 mL/minute: 150 micrograms once daily or 500 mcg every 72 hours in nucleoside treatment-naive patients; 300 micrograms once daily in lamivudine-refractory patients.
CC less than 10 mL/minute: 50 micrograms once daily or 500 mcg every 5 to 7 days in nucleoside treatment-naive patients; 100 micrograms once daily 500 mcg every 72 hours in lamivudine-refractory patients.
Patients receiving haemodialysis should receive the appropriate dose after each dialysis session.
Severe exacerbation of hepatitis B has been reported after stopping treatment with entecavir and hepatic function should be monitored closely, with both clinical and laboratory follow-up for several months, after treatment is discontinued. Dosage reduction may be necessary in patients with renal impairment.
The most common adverse effects of entecavir have been headache, fatigue, dizziness, and nausea. Lactic acidosis, usually associated with severe hepatomegaly and steatosis, has been associated with treatment with nucleoside reverse transcriptase inhibitors. Entecavir is carcinogenic in rodents, but a relationship with human cancer has not been established.
Store at temperatures not exceeding 30°C.
J05AF10 - entecavir ; Belongs to the class of nucleoside and nucleotide reverse transcriptase inhibitors. Used in the systemic treatment of viral infections.