Acyclovir - An Antiviral Agent

Aciclovir (ACV), also known as Acyclovir, is an antiviral drug which is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles. Acyclovir can also be used to prevent cytomegalovirus infections following transplant and also to prevent complications of Epstein-Barr virus infection. It can be taken by mouth, applied as a cream, or injected.


Molecular Structure

Acyclovir - An Antiviral Agent

Class of Drug

Antiviral agent

Mechanism of Action

Nucleotide analog; inhibits viral replication by termination of viral DNA chain and inhibition and inactivation of viral DNA polymerase.

Indications / Dosage / Route

Routes of Administration: Oral and IV.

Condition: Herpes simplex (HSV-1 and HSV-2) infections (immunocompromised host)

Dose: Adults, Children >12 years: IV 5 mg / kg (infuse at constant rate over 1 hour), q8h for 7 days.
For Children <12 years: IV 250 mg/m2 (infuse at constant rate for 1 hour), q8h.

Condition: Genital herpes

Dose: Adults, Children >12 years: PO 200 mg q4h, five doses/day; 10 days for initial therapy. Dose for 5 days for intermittent recurrent disease. Administer up to 12 months for chronic disease (suppressive therapy).
For Children <12 years: IV 250 mg/m2, t.i.d. for 10 days.

Condition: Herpes simplex encephalitis

Dose: Adults, Children >12 years: IV 10 mg/kg (infuse at constant rate over 1 hour), q8h for 10 days.
For Children, 6 months to 12 years: IV 500 mg/m2 (infuse at constant rate over 1 hour), q8h for 10 days.

Condition: Herpes zoster

Dose: Adults, Children >12 years: PO 80 mg, q4h, five doses/day, 7–10 days.
For Children <12 years: PO 250–600 mg/m2, 4–5 times/day, 7–10 days.

Condition: Chickenpox

Dose: Adults, Children >40 kg: PO 800 mg, q.i.d. 5 days.
For Children >2 years: PO 20 mg/kg q.i.d. (maximum 800 mg), 5 days.


Adjustment of Dosage

Kidney disease: Creatinine clearance 25–50 mL/min: dose q12h; creatinine clearance 10–25 mL/min: dose q24h; creatinine clearance <10 mL/min: half dose q24h (IV doses).

Liver disease: None.

Elderly: None.

Pediatric: Safety has not been established in children <2 years old.

Food and Drug Interactions

Food: No restrictions.

Pregnancy: Category C.

Lactation: Appears in breast milk; considered compatible by American Academy of Pediatrics.

Contraindications: Hypersensitivity to acyclovir.

Drug Interactions:

  • Drugs that increase effects/toxicity of acyclovir: MAO inhibitors, probenecid, ziduvine, CNS depressants.
  • Drugs that decrease effects/toxicity of acyclovir: β blockers, guanethidine.


Warnings / Precautions

  • Use with caution in patients with the following conditions: kidney disease, neurologic disease.
  • Beware of renal dysfunction especially if patient is taking other nephrotoxic drugs.
  • Women with genital herpes should have annual Pap smears.
  • Rapid bolus administration may cause crystalline precipitation in renal tubules and renal insufficiency.
  • Patients receiving acyclovir IV must remain well hydrated during treatment and for 24 hours after treatment.
  • Cases of thrombotic thrombocytopenic purpura/hemolytic uremia syndrome have been reported with high-dose acyclovir in immunocompromised patients.

Adverse Effects

Common: headache, phlebitis (IV only).

Serious: seizures, renal failure, anaphylaxis, encephalopathy (confusion, hallucinations), coma, leukopenia, renal crystalline precipitant, elevated liver enzymes, Stevens–Johnson syndrome, urticaria.

Advise to Patient

  • Drink 2–3 L of fluid per day. This is particularly important following IV infusion.
  • Avoid sexual intercourse when lesions are present; otherwise use condoms.
  • Avoid contact of the drug with or around the eyes.
  • Resume treatment at first indication of recurrence of infection.

Parameters to Monitor

  • Serum BUN and creatinine, CBC with differential and platelets, liver enzymes.
  • Signs and symptoms of ocular herpetic infection as this may cause blindness.
  • Serum creatinine level: If this increases during therapy, adjust dose, increase hydration or discontinue drug.
  • Signs and symptoms of hepatotoxicity.
  • Signs and symptoms of renal toxicity.
  • Signs and symptoms of drug-induced psychologic disturbances: Changes in mood, behavior or orientation of patient, agitation, hallucinations, suicidal tendencies, sleep disturbances, lethargy.
  • Intake of fluids and urinary and other fluids. Closely monitor electrolyte levels.

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