Generic
Acyclovir
38 brands available in the market
At a glance
Acyclovir is an antiviral medication used to treat herpes simplex virus infections, chickenpox, shingles and genital herpes. It prevents viral multiplication and helps clear the infection.
Description
Acyclovir is a synthetic purine nucleoside analogue active against herpes simplex virus types 1 and 2 and varicella-zoster virus. It is converted by viral thymidine kinase to acyclovir monophosphate, which is further converted to diphosphate and active triphosphate by cellular enzymes. This active form inhibits viral DNA synthesis and replication by interfering with viral DNA polymerase and incorporating into viral DNA.
Indications
Herpes simplex virus infections (genital herpes, herpes labialis), chickenpox (varicella), shingles (herpes zoster).
Therapeutic class
Antiviral
Pharmacological class
Nucleoside Analogue
Pharmacology
Acyclovir is activated by viral thymidine kinase to form acyclovir triphosphate. This triphosphate competitively inhibits viral DNA polymerase and incorporates into growing DNA chains causing chain termination, thereby stopping viral DNA replication.
Mechanism of action
Acyclovir is activated inside viral cells to inhibit viral DNA polymerase and incorporate into growing DNA chains, stopping viral DNA replication and preventing viral growth and spread.
Dosage
Herpes Simplex (Oral):
- Adults: 200-400 mg 3-5 times daily for 5-10 days.
- Children: 900 mg/m2/day every 8 hours (max 4 g/day).
Genital Herpes (Initial):
- Adults: 200 mg 5 times daily for 10 days OR 400 mg 3 times daily for 7-10 days.
Genital Herpes (Recurrent):
- Adults: 200 mg 5 times daily for 5 days OR 400 mg 3 times daily for 5 days OR 800 mg twice daily for 5 days.
Genital Herpes Suppression (Maintenance):
- Adults: 400 mg twice daily.
Herpes Labialis (Cold Sores):
- Adults: 400 mg 3 times daily for 5 days OR 200 mg 5 times daily for 5 days.
Shingles (Herpes Zoster):
- Adults: 800 mg 5 times daily (every 4 hours) for 7-10 days.
Chickenpox (Children):
- >2 years: 60-80 mg/kg/day (max 4 g/day) every 6-8 hours for 5 days.
Renal Adjustment: Adjust dose based on creatinine clearance.
Administration
Oral: Swallow tablet whole; do not crush. Can be taken with or without food. Drink adequate water to prevent dehydration and kidney damage.
Suspension Reconstitution: Shake bottle well, add cooled boiled water to the mark, shake until completely mixed.
IV Infusion Reconstitution: Add 10 mL or 20 mL sterile water for injection to 500 mg or 1000 mg vial respectively to make 50 mg/mL solution, then dilute with 50-125 mL compatible IV infusion solution.
Missed dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not double the dose.
Side effects
Common side effects: Headache, dizziness, nausea, vomiting, fatigue, fever, abdominal pain, diarrhea, skin rash, photophobia.
Serious (rare): Kidney damage (especially in dehydrated or renal impaired patients), neurological effects (confusion, hallucinations, seizures), elevated liver enzymes.
Precautions & warnings
- Maintain adequate hydration (prevents kidney damage)
- Consult your doctor during pregnancy and lactation
- Use condoms and avoid sexual contact while genital herpes lesions are present
- Dose adjustment needed in renal impairment
- Does not usually affect driving ability
Contraindications
Hypersensitivity to acyclovir.
Drug interactions
- Probenecid: May increase acyclovir levels.
- Methotrexate: May increase toxicity.
- Theophylline: May increase serum concentration.
- Tenofovir: May increase acyclovir levels.
Food interactions
Information on alcohol consumption is not available; consult your doctor.
Use in pregnancy
Generally considered safe during pregnancy (Pregnancy Category: B). Animal studies have shown low or no adverse effects on the fetus; human studies are limited.
Pregnancy Category: B — always consult a doctor before taking during pregnancy.
Use in lactation
Acyclovir is excreted in breast milk but not in significant amounts and is considered not harmful to the baby.
Pediatric use
Pediatric doses are weight and age-based (see dosage section above).
Geriatric use
Dose adjustment may be needed for elderly patients (due to reduced renal function).
Renal / hepatic impairment
Renal impairment: Caution required; dose adjustment may be needed. Maintain adequate hydration. Adjust dose based on creatinine clearance:
- CrCl >25 mL/min: Normal dose
- CrCl 10-25 mL/min: 800 mg every 8 hours
- CrCl 0-10 mL/min: 800 mg every 12 hours
Hepatic impairment: Probably safe; dose adjustment may not be needed.
Overdose effects
Overdose symptoms: nausea, vomiting, diarrhea, confusion, renal impairment. Treatment: symptomatic and supportive measures; hemodialysis is effective.
Storage conditions
Store in a cool and dry place, protected from light. Keep out of reach of children.
Chemical structure
C₈H₁₁N₅O₃