What is the most important information I should know about acyclovir?
• Use this medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated.
• Treatment with acyclovir should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).
• Herpes infections are contagious and you can infect other people, even while you are being treated with acyclovir. Avoid letting infected areas meet other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Aciclovir is poorly water-soluble and has poor oral bioavailability (10–20%); hence, intravenous administration is necessary if high concentrations are required. When orally administered, peak plasma concentration occurs after 1–2 hours. Aciclovir has a high distribution rate, only 30% is protein-bound in plasma. The elimination half-life of aciclovir is approximately 3 hours. It is renally excreted, partly by glomerular filtration and partly by tubular secretion.

How should this medicine be used?

Acyclovir comes as a tablet, a capsule, and a suspension (liquid) to take by mouth. It is usually taken with or without food two to five times a day for 5 to 10 days, starting as soon as possible after your symptoms begin. When acyclovir is used to prevent outbreaks of genital herpes, it is usually taken two to five times a day for up to 12 months. Take acyclovir at around the same times every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take acyclovir exactly as directed. Do not take more or less of it or take it more often or for a longer time than prescribed by your doctor.

Shake the liquid well before each use to mix the medication evenly.

Your symptoms should improve during your treatment with acyclovir. Call your doctor if your symptoms do not improve or if they get worse.

Take acyclovir until you finish the prescription, even if you feel better. If you stop taking acyclovir too soon or skip doses, your infection may not be completely treated or may become more difficult to treat.

Systemic therapy

Common adverse drug reactions (≥1% of patients) associated with systemic aciclovir therapy (oral or IV) include nausea, vomiting, diarrhea and/or headache. In high doses, hallucinations have been reported. Infrequent adverse effects (0.1–1% of patients) include: agitation, vertigo, confusion, dizziness, edema, arthralgia, sore throat, constipation, abdominal pain, rash and/or weakness. Rare adverse effects (<0.1% of patients) include: coma, seizures, neutropenia, leukopenia, crystalluria, anorexia, fatigue, hepatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis and/or anaphylaxis.

Additional common adverse effects, when aciclovir is administered IV, include encephalopathy (1% of patients) and injection site reactions. The injection formulation is alkaline (pH 11), and extravasations may cause local tissue pain and irritation. Renal impairment has been reported when aciclovir is given in large, fast doses intravenously, due to the crystallization of aciclovir in the kidneys.

Indication: Herpes genitals, herpes simplex, herpes zoster

Drug Interactions: Genital herpes is a sexually transmitted disease and patients should avoid intercourse when they have visible lesions. Resistance to acyclovir can develop, especially with overuse. Therefore, acyclovir should be used only for severe cases and only as long as needed. Long-term suppression for recurrent genital herpes should include periodic re-evaluations and trials without the drug or intermittent short-term treatments.