Docosanol

Mechanism and history of antiviral drug usage

Docosanol is thought to act by inhibiting the fusion of the human host cell with the viral envelope of the herpes virus, thus preventing its replication. This mechanism has not been demonstrated empirically.

The drug was licensed as a cream for oral herpes after clinical trials by the FDA in July 2000. It was shown to shorten the healing by 17.5 hours on average (95% confidence interval: 2 to 22 hours) in a placebo-controlled trial. Another trial showed no effect when treating the infected backs of guinea pigs.

Two experiments with n-docosanol cream failed to show statistically significant differences by any parameter between n-docasonol cream and vehicle control–treated sites or between n-docosanol and untreated infection sites.

Marketed by Avanir Pharmaceuticals, Abreva was the first but not the only over-the-counter antiviral drug approved for sale in the United States and Canada. In Europe, it is marketed by Healthcare Brands under the name Erazaban. In the UK it is known by the name "Blistex Cold Sore Cream". In March 2007 it was the subject of a US nationwide class-action suit against Avanir and GlaxoSmithKline as the claim that it cut recovery times in half was found to have been misleading in a California court, but the case was eventually settled and the "cuts healing time in half" claim had not been used in product advertising for some years.

Side effects

One of the most common side effects that has been reported from docosanol is headache. Headaches caused by the drug tend to be mild and can occur in any region of the head. The intensity of the pain can, in some cases, interfere with the ability of remaining focused when working or when at school.

Skin irritation may also occur at the site of application. Usually, skin irritation is mild to moderate and does not need any further treatment. It may also diminish after prolonged use of docosanol.

The most serious side effects, although rare, are allergic reactions. Some of the patients experienced the symptoms of allergic reactions, including difficulty breathing, confusion, facial swelling, fainting, dizziness, hives or chest pain. Allergic reactions are medical emergencies and individuals who experience them are advised to seek immediate medical care in order to prevent further complications.

Other side effects may include: acne, burning, dryness, itching, rash, redness, acute diarrhea, soreness, swelling.

Contraindications

This topical has not been yet tested if it is safe to be used by pregnant women. It is not established whether the active ingredient in the medicine passes into the breast milk. Docosanol has not been specifically approved for treatment of children under 12 but is not expected to produce different side effects or problems than it does in adults. This topical is only intended for external, oral-facial use and not for genital herpes or shingles.

Cosmetic products are recommended to be avoided while using docosanol mainly because they are likely to spread the unhealed infection and not because they interact with the topical.