ACYCLOVIR

Acyclovir is a synthetic nucleoside analogue active against herpes viruses. Acyclovir ointment USP 5% is a formulation for topical administration. Each gram of acyclovir ointment USP, 5% contains 50 mg of acyclovir USP in a polyethylene glycol (PEG) base. Acyclovir USP 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 225.2 g/mol. The maximum solubility in water at 37°C is 2.5 mg/mL. The pka’s of acyclovir are 2.27 and 9.25. The chemical name of acyclovir USP is 2-amino-1, 9-dihydro-9- [(2-hydroxyethoxy)methyl]-6 H- purin-6-one; it has the following structural formula: structure.jpg

Acyclovir ointment 5% is indicated in the management of initial genital herpes and in limited non-life-threatening mucocutaneous Herpes simplex virus infections in immunocompromised patients.

Apply sufficient quantity to adequately cover all lesions every 3 hours, 6 times per day for 7 days. The dose size per application will vary depending upon the total lesion area but should approximate a one-half inch ribbon of ointment per 4 square inches of surface area. A finger cot or rubber glove should be used when applying acyclovir ointment to prevent autoinoculation of other body sites and transmission of infection to other persons. Therapy should be initiated as early as possible following onset of signs and symptoms.

Acyclovir ointment 5% is contraindicated in patients who develop hypersensitivity to the components of the formulation.

In the controlled clinical trials, mild pain (including transient burning and stinging) was reported by about 30% of patients in both the active and placebo arms; treatment was discontinued in 2 of these patients. Local pruritus occurred in 4% of these patients. In all studies, there was no significant difference between the drug and placebo group in the rate or type of reported adverse reactions nor were there any differences in abnormal clinical laboratory findings. Observed During Clinical Practice Based on clinical practice experience in patients treated with acyclovir ointment in the US, spontaneously reported adverse events are uncommon. Data are insufficient to support an estimate of their incidence or to establish causation. These events may also occur as part of the underlying disease process. Voluntary reports of adverse events that have been received since market introduction include: General: Edema and/or pain at the application site. Skin: Pruritus, rash.

Clinical experience has identified no interactions resulting from topical or systemic administration of other drugs concomitantly with acyclovir ointment 5%.