Class: Viral DNA Polymerase Inhibitor
Dosage Forms. Capsule: 200 mg; Suspension: 200 mg/5 mL; Tablet: 400 mg, 800 mg
Common FDA Label Indication, Dosing, and Titration.
1. Genital herpes simplex: Adults, initial episode, 400 mg po tid or 200 mg po 5 times a day × 7-10 d; Children 12 y and older, 1000-1200 mg/d po in 3-5 divided doses for 7-10 d
2. Genital herpes simplex, suppressive therapy: 400 mg po bid for up to 12 mo
3. Herpes zoster, shingles: 800 mg po q4h 5 times a day × 7-10 d
4. Varicella: Adults, 800 mg po qid × 5 d; Children 2 y and older, 20 mg/kg po qid × 5 d; Children over 40 kg, 800 mg po qid × 5 d
1. Genital herpes simplex-HIV infection, initial or recurrent: 400 mg po tid × 5-14 d
2. Genital herpes simplex-HIV infection, chronic suppression of frequent or severe recurrences: 400 mg po bid
MOA. Acyclovir is an acyclic nucleoside analogue of deoxyguanosine that is selectively phosphorylated by the virus-encoded thymidine kinase to its monophosphate form. Cellular enzymes then convert the monophosphate to the active antiviral acyclovir triphosphate, which inhibits viral DNA synthesis by incorporation into viral DNA, resulting in chain termination. Acyclovir has potent activity against herpes simplex virus (HSV) I and II and herpes zoster virus (varicella-zoster virus [VZV]).
Drug Characteristics: Acyclovir
Medication Safety Issues: Acyclovir
Drug Interactions: Acyclovir
Adverse Reactions: Acyclovir
Efficacy Monitoring Parameters. Resolution of clinical signs of infection (lesions) within 2-3 d.
Toxicity Monitoring Parameters. Seek medical attention if decreased urination, unusual bruising or bleeding, blistering skin rash, or shortness of breath.
Key Patient Counseling Points. Complete full course of therapy. Ensure adequate hydration. Symptoms should improve within 2-3 d; if they worsen, seek follow-up with healthcare practitioner. If using for prophylaxis, this medication should reduce the number of breakouts.
Clinical Pearls. Not indicated for children <2 y of age. Use caution with concurrent nephrotoxins.