Entecavir
Mechanism :
By competing with the natural substrate deoxyguanosine triphosphate, entecavir functionally inhibits all three activities of the 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.
Indication :
- Chronic hepatitis B virus infection
Contraindications :
Hypersensitivity, Patients with HIV who are not receiving HAART.
Dosing :
<2 years:
Safety and efficacy not established. To be taken on an empty stomach.
>2 years:
Nucleoside-naive: 0.5 mg orally every day. In
lamivudine or
telbivudine known resistant mutation: 1 mg orally every day.
Adverse Effect :
Fatigue, headache, dizziness, nausea, diarrhea, dyspepsia, vomiting, somnolence, insomnia, lactic acidosis, increased transaminases.
Interaction :
Drugs that reduce Renal Function or Compete for Active Tubular Secretion: Coadministration with entecavir may increase serum concentrations of either entecavir or the co administered drug.
Lamivudine, Adefovir Dipivoxil, or Tenofovir Disoproxil Fumarate: Coadministration with entecavir did not result in significant drug interactions.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 30-50 | 250 mcg daily; 500 mcg daily in lamivudine-refractory patients |
| 10-30 | 150 mcg daily; 300 mcg daily in lamivudine-refractory patients |
| <10 | 50 mcg daily; 100 mcg daily in lamivudine-refractory patients |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | 0.3% dialysed. Dose as in GFR<10 mL/min |
| HD | 13% dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Dialysed. Dose as in GFR<10 mL/ min |
| CAV/VVHD | Likely to be dialysed. Dose as in GFR=10–30 mL/min |
Hepatic Dose :
No dosage adjustments are recommended.