Acyclovir is an antiviral drug active against herpes simplex virus. Acyclovir is a synthetic purine nucleoside analogue with cell culture and in vivo inhibitory activity against HSV types 1 (HSV-1) and 2 (HSV-2). The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV. This viral enzyme converts acyclovir into acyclovir monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In cell culture, acyclovir triphosphate stops replication of herpes viral DNA. This inhibition is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation into and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase.

Acyclovir cream is a herpes simplex virus (HSV) nucleoside analogue DNA polymerase inhibitor indicated for the treatment of recurrent herpes labialis (cold sores) in immunocompetent adults and adolescents 12 years of age and older.

Acyclovir cream should be applied five times per day for four days. Therapy should be initiated as early as possible following the onset of signs or symptoms of herpes labialis i.e., during the prodrome or when lesions appear. For adolescents 12 years of age and older, the dosage is the same as in adults.

Acyclovir cream is contraindicated in patients with known hypersensitivity to acyclovir, valacyclovir, or any component of the formulation.

The most common adverse reactions at the site of topical application were dry lips, desquamation, dryness of skin, cracked lips, burning skin, pruritus, flakiness of skin, and stinging on skin; each adverse reaction occurred in less than 1% of patients receiving Acyclovir cream and placebo. Three patients on Acyclovir cream and one patient on placebo discontinued treatment due to an adverse event.

Pregnancy & Lactation

Pregnancy Category B. There are no adequate and well-controlled studies of acyclovir cream in pregnant women. Acyclovir cream should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is not known whether topically applied acyclovir is excreted in breast milk. Systemic exposure following topical administration is minimal.

Precautions & Warnings

Acyclovir cream should only be applied on the affected external aspects of the lips and face in patients with herpes labialis. Because no data are available, application to human mucous membranes is not recommended. Acyclovir cream is intended for cutaneous use only and should not be used in the eye or inside the mouth or nose. Cream has a potential for irritation and contact. The effect of Acyclovir cream has not been established in immunocompromised patients.