Common Brand Names: Zovirax
Therapeutic Class: A synthetic deoxyguanosine analog antiviral agent.
Common Injectable Dosage Forms:
Powder for Injection: 500 mg and 1-gram vials
Solution for Injection: 50 mg/mL
Neonates (birth to 3 months): 10 mg/kg/dose every 8 hours for 10 days; 15-20 mg/kg/dose every 8 hours for 14-21 days.
Children (<12 days): 10-20 mg/kg/dose every 8 hours for 7-10 days OR 250 mg/m^2/dose every 8 hours OR 125 mg/m^2/dose every 6 hours.
12 and older: 5-10 mg/kg/dose every 8 hours for 7-21 days OR 500 mg/m^2/dose every 8 hours for 7-21 days.
Administration and Stability:
Reconstitute by adding sterile water to produce concentration of 50 mg/mL. Further dilute to final concentration no greater than 7 mg/mL. Further concentrations (e.g., 10 mg/mL) often results in phlebitis. Infuse over 1 hour to prevent adverse renal effects. Stability of 50 mg/mL solution is 12 hours and 24 hours after further dilution for administration. Do not refrigerate or use bacteriostatic water for injection as a precipitate will form. PH ~11
Pharmacology/Pharmacokinetics:
The drug appears to interfere with viral replication by acting as a false nucleotide in DNA chains. Acyclovir is active against various Herpes viridae including Herpes simplex, Varicella zoster, and cytomegalovirus. Several mechanisms of resistance appear to exist. The drug is widely distributed in body fluids and tissues, protein binding is negligible, and it achieves good penetration in the cerebral spinal fluid. The elimination half-life is 2.5-3.3 hours with most of the drug excreted in the urine in the first 24 hours.
Drug and Lab Interactions:
Concomitant use with zidovudine may antagonize HIV antiretroviral activity, and also increases the risk of hematologic toxicity. Renal impairment may result from concomitant use with other nephrotoxic agents. Probenecid has been shown to potentiate plasma half-life of acyclovir.
Contraindications/Precautions:
Contraindicated in patients with known hypersensitivity to acyclovir or ganciclovir. Acyclovir therapy is often associated with neurologic toxicity and frequent monitoring should be performed. Adequate hydration should be ensured during therapy. Pregnancy Category B.
Monitoring Parameters:
Cr, BUN
Adverse Effects:
The most common adverse reaction of parenteral administration is local reaction at the site of injection. This may usually be avoided by administrating at concentrations of less than 7 mg/mL. Other reported effects include headache, rash, impaired renal function, nausea, and vomiting.
Common Clinical Applications:
Effective in treatment of herpes simplex initial and recurrent infections, some cases of genital herpes, herpes simplex encephalitis, and varicella zoster infection in adults and children.