ACYCLOVIR

Acyclovir, a synthetic deoxynucleoside analogue active against herpes viruses. Acyclovir cream, 5% is a formulation for topical administration. The chemical name of acyclovir is 2-amino-1,9-dihydro-9-[(2-hydroxyethoxy) methyl]-6 H -purin-6-one; it has the following structural formula: Acyclovir is a white to off-white, crystalline powder with the molecular formula C 8 H 11 N 5 O 3 and a molecular weight of 225. The maximum solubility in water at 37°C is 2.5 mg/mL. The pKa's of acyclovir are 2.27 and 9.25. Each gram of acyclovir cream, 5% contains 50 mg (equivalent to 5% w/w) of acyclovir and the following inactive ingredients: cetostearyl alcohol, mineral oil, poloxamer 407, propylene glycol, sodium lauryl sulfate, water, and white petrolatum. Chemical Structure

Acyclovir cream is a herpes simplex virus (HSV) deoxynucleoside 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, 5% is a herpes simplex virus (HSV) deoxynucleoside 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. ( 1 )

Acyclovir cream should be applied 5 times per day for 4 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. Apply 5 times a day for 4 days. ( 2 ) Administer immediately following the onset of cold sore lesions. ( 2 )

Acyclovir cream is contraindicated in patients with known hypersensitivity to acyclovir, valacyclovir, or any component of the formulation. Acyclovir cream is contraindicated in patients with known hypersensitivity to acyclovir, valacyclovir or any component of the formulation. ( 4 )

The most common adverse reactions reported were local skin reactions at the application site. ( 6.1 ) Angioedema, anaphylaxis, contact dermatitis and eczema have been reported. ( 6.2 ) To report SUSPECTED ADVERSE REACTIONS, contact Taro Pharmaceuticals U.S.A., Inc. at 1-866-923-4914 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug, and may not reflect the rates observed in practice. In five double-blind, placebo-controlled trials, 1124 patients were treated with acyclovir cream and 1161 with placebo (vehicle) cream. Local application site reactions were reported by 5% of patients receiving acyclovir cream and 4% of patients receiving placebo. 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. An additional study, enrolling 22 healthy adults, was conducted to evaluate the dermal tolerance of acyclovir cream compared with vehicle using single occluded and semi-occluded patch testing methodology. Both acyclovir cream and placebo showed a high and cumulative irritation potential. Another study, enrolling 251 healthy adults, was conducted to evaluate the contact sensitization potential of acyclovir cream using repeat insult patch testing methodology. Of 202 evaluable subjects, possible cutaneous sensitization reactions were observed in the same 4 (2%) subjects with both acyclovir cream and placebo, and these reactions to both acyclovir cream and placebo were confirmed in 3 subjects upon rechallenge. The sensitizing ingredient(s) has not been identified. The safety profile in patients 12 to 17 years of age was similar to that observed in adults. 6.2 Postmarketing Experience In addition to adverse events reported from clinical trials, the following events have been identified during postapproval use of acyclovir cream. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to acyclovir cream. General: Angioedema, anaphylaxis. Skin: Contact dermatitis, eczema.

Clinical experience has identified no interactions resulting from topical or systemic administration of other drugs concomitantly with acyclovir cream. Due to minimal systemic absorption of acyclovir cream, systemic drug interactions are unlikely. Clinical experience has identified no interactions resulting from topical or systemic administration of other drugs concomitantly with acyclovir cream. Due to minimal systemic absorption of acyclovir cream, systemic drug interactions are unlikely. ( 7 )

Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].