Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: acyclovir

BRAND NAME: Zovirax

DRUG CLASS AND MECHANISM: Acyclovir 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 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.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS:

• Capsules: 200 mg.
• Tablets: 400 and 800 mg.
• Suspension: 200 mg/5 ml.
• Injection: 50 mg/ml.
• Powder for injection: 500 and 1000 mg.
• Ointment 5%.

STORAGE: Acyclovir should be stored at room temperature, between 15-25 C (59-77 F).

PRESCRIBED FOR: Oral Acyclovir is used for treating genital herpes, herpes zoster, and chickenpox. Acyclovir 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 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 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 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 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.

Reference: FDA Prescribing Information

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