Acyclovir – Complete Guide

When dealing with acyclovir, an antiviral drug that stops the replication of certain viruses. Also known as Zovirax, it is a cornerstone in treating infections caused by Herpes Simplex Virus, the virus behind cold sores and genital herpes and Varicella‑Zoster Virus, the agent of chicken‑pox and shingles. The drug works by inhibiting viral DNA polymerase, which halts the virus‑to‑cell replication cycle. Because it targets a step common to both HSV and VZV, acyclovir can be given as tablets, topical creams, or intravenous infusions, each suited to a different severity level. Oral tablets are the go‑to for mild to moderate outbreaks, while IV dosing is reserved for severe cases such as encephalitis or immunocompromised patients. Topical forms are handy for early‑stage cold sores, delivering the drug directly to the skin and reducing systemic exposure. Dosing usually follows a weight‑based schedule: adults often take 200‑400 mg five times daily for an outbreak, whereas prophylactic regimens may be lower but taken continuously. The medication’s safety profile is solid; most side effects are mild, like headache or nausea, but kidney function should be checked in patients with pre‑existing renal disease because the drug is cleared renally.

Practical Insights and What Comes Next

Beyond the basics, several related concepts shape how acyclovir is used in real life. Antiviral medication, a drug class that includes acyclovir, famciclovir, and valacyclovir shares the same goal of suppressing viral replication, yet each has a different bioavailability and dosing convenience. Resistance can emerge, especially in patients with weakened immune systems; resistant strains often show mutations in the viral thymidine kinase gene, making the drug less effective. In such cases, switching to newer agents or using higher IV doses becomes necessary. Vaccination against VZV (the shingles vaccine) reduces the incidence of reactivation, but breakthrough cases still occur, and acyclovir remains the frontline treatment for those episodes. Pregnancy and pediatric use require special attention: the drug crosses the placenta but is considered relatively safe, while children need weight‑adjusted dosing to avoid toxicity. Interactions are modest, though combining acyclovir with nephrotoxic drugs like aminoglycosides can increase kidney strain. Understanding these nuances helps clinicians decide when to start treatment, how long to continue it, and when to monitor labs. Below you’ll find a curated set of articles that dive deeper into dosing strategies, side‑effect management, comparisons with other antivirals, and real‑world case studies, giving you a full picture of how to use acyclovir effectively.