Indications of Enviral 1 mg
Enviral 1 mg is indicated for the treatment of chronic hepatitis B virus infection in adults and pediatric patients 2 years of age and older with evidence of active viral replication and either evidence of persistent elevation in serum aminotransferases (ALT or AST) or histologically active disease.
Hepatic viral infections (Hepatitis B)
Enviral 1 mg is a guanosine nucleoside analogue with potent and selective activity against HBV polymerase. For pharmacological action it is phosphorylated to the active triphosphate (TP) form. Enviral 1 mg triphosphate functionally inhibits all 3 activities of the viral polymerase-
Priming of the HBV polymerase,
Reverse transcription of the negative strand from the pregenomic messenger RNA
Synthesis of the positive strand HBV DNA.
Dosage & Administration of Enviral 1 mg
Administration of Enviral 1 mg with food decreases absorption and so it should be taken in an empty stomach (at least 2 hours before or 2 hours after meal). Adult over 16 years, not previously treated with nucleoside analogues: 0.5 mg once daily.Adult over 16 years with lamivudine or telbivudine resistant chronic hepatitis B: 1 mg once daily.
Dosage of Enviral 1 mg
The recommended dose of Enviral 1 mg for chronic hepatitis B virus infection in nucleoside-treatment-naive adults and adolescents 16 years of age is 0.5 mg once daily. For Lamivudine-refractory or known Lamivudine or Telbivudine resistance mutations, the recommended dose of Enviral 1 mg is 1 mg once daily. For patients with decompensated liver disease (adult) the recommended dose of Enviral 1 mg is 1 mg once daily. Enviral 1 mg should be administered on an empty stomach (at least 2 hours after a meal or 2 hours before the next meal).Missed Dose: If it is almost time for next dose, skip the missed dose and take the next dose at the proper time. Nobody should take a double dose to make up for the missed dose.
Interaction of Enviral 1 mg
Co-administration of Enviral 1 mg with Lamivudine or Adefovir dipivoxil did not result in significant drug interactions. The effects of co-administration of Enviral 1 mg with other drugs that are eliminated through renal or are known to affect renal function have not been evaluated and patients should be monitored closely for adverse events when coadministered with such drugs.
Enviral 1 mg is contraindicated in patients with previously demonstrated hypersensitivity to Enviral 1 mg or any component of the product.
Side Effects of Enviral 1 mg
The most common adverse events are headache, fatigue, dizziness and nausea.
Pregnancy & Lactation
Use in pregnancy: There are no adequate and well-controlled studies in pregnant women. Enviral 1 mg should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.Use in lactation: It is not known whether Enviral 1 mg is excreted in human milk. Mothers should be instructed not to breast-feed if they are taking Enviral 1 mg.
Precautions & Warnings
Lactic acidosis: Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases have been reported with the use of nucleoside analogues alone or in combination with antiretrovirals. Exacerbations of hepatitis after discontinuation of treatment: Severe acute exacerbations of hepatitis B have been reported in patients who have discontinued anti-hepatitis B therapy, including Enviral 1 mg.
Overdose Effects of Enviral 1 mg
There is no experience of Enviral 1 mg overdosage reported in patients. Healthy subjects who received up to 20 mg daily for up to 14 days and single doses up to 40 mg had no unexpected adverse events. If overdosage occurs, the patient must be monitored for evidence of toxicity and standard supportive treatment as necessary.
Keep in a dry place and store below 30°C. Protect from light and keep out of the reach of children.
Use In Special Populations
Use in pediatric patient: Safety and effectiveness of Enviral 1 mg in pediatric patients below the age of 16 years have not been established.Use in geriatric patient: Enviral 1 mg is significantly excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.Dose adjustment in renal impairment: Dose adjustment is recommended for patients with CrCl <50 ml/min including patients on hemodialysis or continuous ambulatory peritoneal dialysis (CAPD) as shown in the following table.CrCl ≥50 ml/min: 0.5 mg every 24 hoursCrCl 30 to <50 ml/min: 0.5 mg every 48 hoursCrCl 10 to <30 ml/min: 0.5 mg every 72 hoursCrCl <10 ml/min or Hemodialysis or CAPD: 0.5 mg every 7 days
Hepatic viral infections (Hepatitis B)
Mode Of Action
By competing with the natural substrate deoxyguanosine triphosphate, Enviral 1 mg functionally inhibits all three activities of the HBV polymerase (reverse transcriptase, rt):
Reverse transcription of the negative strand from the pregenomic messenger RNA, and
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.
There are no data on the effect of Enviral 1 mg on the transmission of HBV from mother to infant. Therefore, appropriate care should be taken. It is not known whether it is excreted in human milk. Mothers should be instructed not to breastfeed if they are taking Enviral 1 mg.
Pediatric: Safety and effectiveness of Enviral 1 mg in pediatric patients below the age of 2 years have not been established.Geriatric: Clinical studies of Enviral 1 mg did not include sufficient numbers of subjects aged 65 years and over to determine whether they respond differently from younger subjects. But care should be taken in dose selection, and it may be useful to monitor renal function. Dose adjustment in renal impairment: Dose adjustment is recommended for patients with CrCl <50 ml/min including patients on hemodialysis or continuous ambulatory peritoneal dialysis (CAPD) as shown below:
CrCl ≥50 ml/min: 0.5 mg every 24 hours
CrCl 30 to <50 ml/min: 0.5 mg every 48 hours
CrCl 10 to <30 ml/min: 0.5 mg every 72 hours
CrCl <10 ml/min or Hemodialysis or CAPD: 0.5 mg every 7 days