Aciclovir
Rx
Therapeutic ClassAntiviral
Common Dose200 mg / 400 mg / 800 mg
RouteOral, IV, Topical
PregnancyCategory B / C (depending on formulation)
Indications ▼
Herpes simplex virus infections (oral and genital)
Varicella-zoster virus infections (chickenpox, shingles)
Prophylaxis in immunocompromised patients
Herpes encephalitis (IV therapy)
Mechanism & Pharmacokinetics ▼
Mechanism: Guanosine analogue that inhibits viral DNA polymerase after phosphorylation by viral thymidine kinase. Selectively inhibits viral replication with minimal effect on host cells.
Pharmacokinetics: Oral bioavailability ~15–30%. Widely distributed in tissues and fluids. Minimal metabolism. Elimination half-life ~2.5–3 hours (adults). Excreted primarily unchanged in urine.
Dosage & Administration ▼
| Patient Group | Dose | Frequency / Duration |
|---|---|---|
| Adults (Oral) | 200–400 mg | 5 times daily for 5–10 days |
| Adults (IV) | 5 mg/kg every 8 hours | 7–14 days depending on severity |
| Pediatric (Oral) | 10 mg/kg | 5 times daily for 5–10 days |
| Topical | 5% cream | Apply 5 times daily for 4–10 days |
Side Effects ▼
Headache, dizziness
Nausea, vomiting
Diarrhea
Rare: Renal dysfunction, thrombocytopenia, hypersensitivity reactions
Contraindications ▼
Hypersensitivity to aciclovir or valaciclovir
Severe renal impairment (adjust dose accordingly)
Drug Interaction ▼
Probenecid may increase plasma concentrations
Nephrotoxic drugs may increase renal risk
Caution with other antivirals affecting renal function
Pregnancy & Lactation ▼
Use only if clearly needed; consult physician
Generally considered compatible with breastfeeding
Clinical / Research Summary ▼
Mechanism of Action: Aciclovir is a nucleoside analogue that inhibits viral DNA polymerase. It is selectively phosphorylated by viral thymidine kinase, incorporated into viral DNA, and causes chain termination, preventing viral replication.
Clinical Uses: Effective against HSV-1, HSV-2, and VZV infections. Used for treatment and prophylaxis of genital herpes, cold sores, shingles, chickenpox, and HSV encephalitis.
Evidence: Multiple randomized controlled trials support aciclovir’s efficacy in reducing lesion duration, pain, and viral shedding in HSV infections. Early IV administration improves outcomes in HSV encephalitis.
Resistance: Rare; usually occurs in immunocompromised patients. Resistance is due to mutations in viral thymidine kinase or DNA polymerase genes.
Pharmacokinetics Insights: Rapid absorption orally (bioavailability 15–30%), distributes widely in body fluids including CSF. Excreted primarily unchanged via kidneys; dose adjustment required in renal impairment.
Research Updates: Recent studies explore high-dose IV therapy for severe VZV infections, combination therapy in resistant HSV, and topical formulations with enhanced skin penetration.
Special Populations: Safe in pregnancy (Category B) and generally well-tolerated in children. Monitor renal function in elderly or those with kidney disease.
Patient Counseling Points ▼
Maintain adequate hydration
Adhere strictly to prescribed duration
Topical application: wash hands before and after use
Report rash, itching, or unusual bleeding
Storage & Handling ▼
Store below 25°C, protect from light and moisture
Keep out of reach of children
Do not freeze
Brand Names (Bangladesh & Global) ▼
Medical Disclaimer: This clinical summary is for educational purposes only. Always consult a qualified healthcare provider before use.
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