Acyclovir

What is acyclovir, and how does it work (mechanism of action)?

Acyclovir is an antiviral drug, a synthetic nucleoside analogue, that has inhibitory activity (interferes with viral replication) 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.

What brand names are available for acyclovir?

Zovirax

Is acyclovir available as a generic drug?

GENERIC AVAILABLE: Yes

Do I need a prescription for acyclovir?

Yes

What are the side effects of acyclovir?

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.

What is the dosage for acyclovir?

Acyclovir may be taken with or without food.

• Adult oral doses for treating genital herpes are 200 mg every 4 hours (5 times daily) for 7-10 days or 400 mg three times daily for 5-10 days.
• Herpes Zoster (shingles) is treated with 800 mg every 4 hours (5 times daily) for 7 to 10 days.
• The dose for treating chicken pox is 800 mg 4 times daily. The usual adult intravenous dose is 5-10 mg/kg every 8 hours for 7-10 days.

Which drugs or supplements interact with acyclovir?

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).
Combining acyclovir with cidofovir (Vistide), amphotericin B (Fungizone) or other drugs that reduce kidney function may increase harmful effects on the kidney.

Is acyclovir safe to take if I'm pregnant or breastfeeding?

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.
Acyclovir is excreted in breast milk, and a significant amount may be transferred to the infant.

What else should I know about acyclovir?

What preparations of acyclovir are available?

• 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%.

How should I keep acyclovir stored?

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

Summary

Acyclovir (Zovirax) is an antiviral drug prescribed to treat genital herpes, shingles, and chickenpox. Side effects drug interactions, dosing, storage, and pregnancy safety information should be reviewed prior to taking this medication.