Indications

Virux 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.

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Pharmacology

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.

Dosage & Administration

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.

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Interaction

Clinical experience has identified no interactions resulting from topical or systemic administration of other drugs concomitantly with Virux cream. Due to minimal systemic absorption of Virux cream, systemic drug interactions are unlikely.

Contraindications

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

Side Effects

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 Virux cream and placebo. Three patients on Virux 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

Virux 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. Virux 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 Virux cream has not been established in immunocompromised patients.

Use in Special Populations

Pediatric Use: An open-label, uncontrolled trial with Virux cream 5% was conducted in 113 patients aged 12 to 17 years with recurrent herpes labialis. In this trial, therapy was applied using the same dosing regimen as in adults and subjects were followed for adverse events. The safety profile was similar to that observed in adults. Safety and effectiveness in pediatric patients less than 12 years of age have not been established.

Geriatric Use: Clinical studies of Virux cream did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. Systemic absorption of Virux after topical administration is minimal.

Therapeutic Class

Topical Antiviral preparations

Storage Conditions

Store Virux cream at room temperature between 20°C to 25°C