DRUG CLASS AND MECHANISM: Acyclovir (Generic Zovirax) is an antiviral drug, a synthetic nucleoside analogue, that is active against the herpes viruses, including herpes simplex 1 and 2 (cold sores and genital herpes), varicella-zoster (shingles and chickenpox), and Epstein-Barr virus (mononucleosis). Viruses take over living cells and reproduce themselves, often at the expense of the host cell. The Acyclovir (Generic Zovirax) is converted to an active form by the virus itself, and the virus then uses the active form of acyclovir rather than the nucleoside it normally uses to manufacture DNA, a critical component of viral replication. Incorporation of active acyclovir into new viral DNA stops the production of the DNA. Virally infected cells absorb more acyclovir than normal cells and convert more of it to the active form, which prolongs its antiviral activity. The FDA approved acyclovir in March 1982.

PREPARATIONS:

• Capsules: 200 mg.

• Tablets: 400 and 800 mg.

PRESCRIBED FOR: Oral Acyclovir (Generic Zovirax) is used for treating genital herpes, herpes zoster, and chickenpox. Acyclovir (Generic Zovirax) reduces the pain and the number of lesions in the initial case of genital herpes, and decreases the frequency and severity of recurrent infections. In the treatment of shingles, acyclovir reduces pain, shortens the healing time, and limits the spread of virus and the formation of new lesions. Acyclovir (Generic Zovirax) can be used to treat chicken pox and acts to reduce healing time, limit the number of lesions, and reduce fever if used within the first 24 hours after the onset of illness. Intravenous acyclovir is used for treating herpes simplex and chicken pox in immuno-compromised patients and severe genital herpes. Acyclovir ointment is used topically to treat initial genital herpes where it has been shown to decrease pain, reduce healing time, and limit the spread of the infection.

DOSING: Acyclovir (Generic Zovirax) may be taken with or without food. Adult oral doses are 200 mg to 800 mg every 4 hours (5 times daily). The usual adult intravenous dose is 5-10 mg/kg every 8 hours for 7 days.

DRUG INTERACTIONS: Acyclovir (Generic Zovirax) may decrease levels of phenytoin (Dilantin) or valproic acid (Depakote, Depakote ER). Probenecid (Benemid) may increase acyclovir serum levels by decreasing renal excretion of acyclovir. Acyclovir may increase serum levels of theophylline (Theo-Dur, Respbid, Slo-Bid, Theo-24, Theolair, Uniphyl, Slo-Phyllin).

PREGNANCY: There are no adequate studies of acyclovir in pregnant women. In a patient registry of women who used acyclovir during the first trimester, the rate of birth defects was similar to the rate of birth defects in the general population.

NURSING MOTHERS:Acyclovir (Generic Zovirax) is excreted in breast-milk, and a significant amount may be transferred to the infant.

SIDE EFFECTS: The most common side effects are nausea, vomiting, diarrhea and headache. Other reported side effects include agitation, confusion, rash, anemia, and muscle pain. Hypersensitivity reactions, seizures, agitation, confusion, anemia, hepatitis, and muscle pain have also been reported.