Aciclovir is a synthetic purine derivative. Aciclovir exerts its antiviral effect on Herpes simplex virus (HSV) and Varicella-zoster virus by interfering with DNA synthesis and inhibiting viral replication. In cells infected with herpes virus, the antiviral activity of Aciclovir appears to depend principally on the intracellular conversion of the drug to Aciclovir Triphosphate. Aciclovir is converted to Aciclovir Monophosphate principally via virus coded thymidine kinase; the monophosphate is phosphorylated to the diphosphate via cellular guanylate kinase and then via another cellular enzyme to the triphosphate, which is the pharmacologically active form of the drug. 15-30% of an oral dose of the drug is absorbed from Gl tract. Peak plasma concentrations usually occur within 1.5-2 hours after oral administration. It is widely distributed into body tissues and fluids including the brain, saliva, lungs, liver, muscle, spleen, uterus, vaginal mucosa and secretions, CSF, and herpetic vesicular fluid. Aciclovir is excreted through the kidney by the glomerular filtration & tubular secretion.

Aciclovir is indicated for-

• The treatment of viral infections due to Herpes simplex virus (type I & II) and Varicella zoster virus (herpes zoster & chicken pox).
• The treatment of Herpes simplex virus infections of the skin and mucous membranes including initial and recurrent genital herpes and herpes labialis.
• The prophylaxis of Herpes simplex infections in immunocompromised patients

Treatment of initial herpes simplex: 200 mg 5 times daily usually for 5 days.

For immunocompromised patients:

• Adult: 400 mg 5 times daily for 5 days (longer if new lesions appear during treatment or if healing is incomplete; increase dose to 800 mg 5 times daily for genital herpes in immunocompromised) or as directed by the registered physician.
• Children under 2 years: Half of the adult dose.
• Children over 2 years: Adult dose.

Prevention of recurrence of herpes simplex:

• Adult: 200 mg 4 times daily or 400 mg twice daily possibly reduced to 200 mg 2 or 3 times daily and interrupted every 6-12 months.
• Children under 2 years: Half of the adult dose.
• Children over 2 years: Adult dose.

Prophylactic treatment of herpes simplex in the immunocompromised patients:

• Adult: 200 to 400 mg 4 times daily.
• Children under 2 years: Half of the adult dose.
• Children over 2 years: Adult dose.

Treatment of vericella (chicken pox):

• Adult and children over 40 kg: 800 mg 4 times daily for 5 days.
• Children below 40 kg: 20 mg/kg (maximum 800 mg) per dose orally 4 times daily (80 mg/kg/day) for 5 days.
• Children 1 month-2 years: 200 mg 4 times daily for 5 days.
• Children 2-5 years:400 mg 4 times daily for 5 days.
• Children 6-12 years:800 mg 4 times daily for 5 days.

Treatment of herpes zoster (Shingles): 800 mg 5 times daily for 7 days.

Treatment of initial rectal (Proctitis) herpes infections: An oral Aciclovir dosage of 400 mg 5 times daily for 10 days or until clinical resolution occurs has been recommended.

Renal Impairment: For patients with severe renal impairment, a reduction of the doses is recommended.

Aciclovir is contraindicated in patients known to be hypersensitive to Aciclovir.

Rash, gastrointestinal disturbance, rise in bilirubin and liver-related enzymes, increase in blood urea and creatinine, decrease in hematological indices, headache, neurological reaction, fatigue.

Pregnancy & Lactation

Pregnancy category B. Aciclovir should not be used during pregnancy unless the potential benefit justifies the potential risk to the fetus. Caution should be exercised when it is administered to a nursing mother.

Precautions & Warnings

Aciclovir should be administered with caution in patients with renal impairment and doses should be adjusted according to creatinine clearance. Monitor neutrophil count at least twice weekly in neonates.