Indications: For the treatment of viral infections due to herpes simplex virus (type I & II) and varicella zoster virus (herpes zoster & chickenpox). For the treatment of herpes simplex virus infections of the skin and mucous membranes including initial and recurrent genital herpes. For the prophylaxis of herpes simplex infections in immunocompromised patients.
Pharmacology: Acyclovir exerts its antiviral effect on herpes simplex viruses (HSV) and varicella-zoster virus by interfering with DNA synthesis and inhibiting viral replication. The exact mechanisms of action against other susceptible viruses have not fully elucidated. In vitro studies with herpes simplex viruses indicate that acyclovir triphosphate is the pharmacologically active form of the drug; the triphosphate functions as both a substrate for and preferential inhibitor of viral DNA polymerase.
Absorption of Acyclovir from the GI tract is variable and incomplete. It is estimated that 15-30% of an oral dose of the drug is absorbed . Acyclovir is widely distributed into body tissues and fluids including the brain, kidney, saliva, lung, liver, muscle, spleen, uterus, vaginal mucosa and secretions, CSF, and herpetic vesicular fluid. The drug is also distributed into semen, achieving concentrations about 1.4 and 4 times those in plasma during chronic oral therapy at dosages of 400 mg and 1 g daily, respectively.
Plasma concentrations of Acyclovir appear to decline in a biphasic manner. In adults with normal renal function, the half-life of acyclovir in the initial phase averages 0.34 hours and the half-life in the terminal phase averages 2.1-3.5 hours.
Dosage & Administration: Tablet: For the treatment of initial and recurrent episodes of herpes simplex infections in adults, 200 mg Acyclovir tablet should be taken 5 times daily (at 4 hours intervals omitting the night-time dose). Treatment should continue for 5 days and may be extended for up to 10 days in severe initial infections. For suppression of herpes simplex infections in adults, treatment with Acyclovir tablet should be continued at a dose of 200 mg 4 times daily or 400 mg twice daily for up to 1 year. If the patient remains recurrence free for up to 2-3 months, this dose can be reduced to 200 mg 3 times daily. After 1 year, treatment should be stopped to reassess patient’s clinical status. For prophylaxis of herpes simplex infections in immune-compromised patients, 200 mg Acyclovir tablet should be taken four times daily at 6 hourly intervals for 7 days. In severely immune-compromised patients (e.g. after bone marrow transplantation) or in patients with impaired absorption from the gut, the dose can be doubled. For treatment of herpes zoster infections in adults, 800 mg Acyclovir tablet should be taken 5 times daily (at 4 hourly intervals) for 7 days.
Interaction: Concomitant administration of probenecid and acyclovir has reportedly increased the mean plasma half-life and decreased urinary excretion and renal clearance of acyclovir. Amphotericin B has been shown to potentiate the antiviral effect of acyclovir against pseudorabies virus in vitro when both drugs are added to the culture medium. Ketoconazole and acyclovir have shown dose-dependent, synergistic, antiviral activity against herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) in in-vitro replication studies.
Contraindications: Acyclovir is contraindicated in patients known to be hypersensitive to acyclovir. For the patients with severe renal impairment, a reduction of the doses is recommended.Therapeutic Class: Antivirals (Systemic Antifungal, Antiviral and Antiprotozoal Agents)Generic Name: AcyclovirManufacturer: Eskayef Bangladesh Ltd৳ 14.00৳ 14.00