Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2017 Publisher: DDD Limited, 94 Rickmansworth Road, Watford, Hertfordshire, WD18 7JJ
Pharmacotherapeutic group: Chemotherapeutics for topical use, antivirals
ATC code: D06BB11
The exact mechanism of the antiviral activity of docosanol is unknown. In vitro studies indicate that docosanol affects the fusion between the virus and the plasma membrane, which inhibits intracellular uptake and replication of virus. In vitro studies demonstrate that docosanol-treated cells resist infection by lipid-enveloped viruses such as HSV-1. Docosanol has no effect against non-enveloped viruses.
Docosanol 10% was compared to placebo (containing polyethylene glycol) in two randomised, double-blind, controlled clinical trials. In one study, 370 adults were randomised. Subjects started with treatment in the prodrome or erythema phase of an acute recurrence of orofacial herpes. The ITT population consisted of 183 subjects for docosanol and 183 subjects for placebo. The median time to complete healing was 4.0 days in the docosanol group and 4.7 days in the placebo group a difference of 18.9 hours (p=0.0235; p=0.010 with covariate adjustment). In the second study, 373 adults were randomised. Subjects started with treatment in the prodrome or erythema phase of an acute recurrence of orofacial herpes. The ITT population consisted of 187 subjects for docosanol and 184 subjects for placebo. The median time to complete healing was 4.3 days in the docosanol group and 4.9 days in the placebo group a difference of 15.9 hours (p=0.1529; p=0,008 with covariate adjustment). In studies with treatment initiation at stages later than the prodromal or erythema stage, efficacy was not demonstrated.
Under conditions reflecting normal clinical use of Blistex Cold Sore Cream, docosanol could not be quantified (limit of quantification, LOQ = 10 ng/ml) in the plasma of treated patients. Ten women with active labial herpes simplex were treated with Blistex Cold Sore Cream. After a single dose on study day 1 and after multiple doses (five times daily, study days 2-3), blood samples were withdrawn up to 24 hours after treatment and analysed for docosanol. Of the 209 plasma samples analysed, the docosanol level was below the LOQ in 208 and exactly at the LOQ in one sample.
Docosanol is metabolized to docosanoic acid, its major metabolite. Both docosanol and docosanoic acid are endogenous components of cell membranes in man, particularly in erythrocytes, brain, nerve myelin sheath, lung, and kidney.
Preclinical data revealed no special hazard for humans based on conventional studies of safety, pharmacology, repeated dose toxicity, genotoxicity and toxicity to reproduction.
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