Aciclovir (Zovirax)

Aciclovir (Zovirax) is a licensed nucleoside analogue drug for treating herpes simplex and varicella zoster virus. It is manufactured by GlaxoSmithKline. It is sometimes referred to by the abbreviation ACV.

Aciclovir is the standard therapy for herpes simplex. In addition, high doses are usually effective for treating hairy leukoplakia.

Some studies have also suggested that aciclovir, either on its own or in conjunction with AZT (zidovudine, Retrovir), may slow down the progression of HIV disease or improve survival, especially for people with low CD4 cell counts. However, this question remains unresolved since other controlled studies have found no evidence that aciclovir does prolong survival.

Several different theories have been proposed to explain why aciclovir could possibly prolong survival:

• Firstly, although aciclovir has no direct anti-HIV effects itself, it has been suggested that it may increase the anti-HIV effect of AZT, although this has not been consistently shown in test tube studies.
• Secondly, aciclovir helps to suppress members of the herpes family of viruses, which may act as co-factors in activating HIV. Stopping or reducing the co-factor effect may therefore delay the progress of HIV disease. However, no herpes virus has yet been shown to act as a co-factor, and trials have shown that even at high doses aciclovir is unable to prevent disease caused by cytomegalovirus, which is the leading co-factor candidate.
• Thirdly, the established value of aciclovir in treating herpes virus infections may in itself enhance the health of people with HIV.

Very few side-effects have been reported from aciclovir. However, it can sometimes cause rashes, gastrointestinal upsets, headache, confusion, fatigue and abnormalities in some blood and liver tests. Intravenous infusions can cause severe inflammation or ulceration at the injection site and neurological problems such as confusion, hallucinations, agitation, convulsions and coma. The combination of AZT (zidovudine, Retrovir) with intravenous aciclovir has been reported to cause extreme lethargy.

Aciclovir does not interact with any protease inhibitors or non-nucleoside reverse transcriptase inhibitors (NNRTIs). Levels of aciclovir can be increased when it is taken at the same time as probenecid. Aciclovir may decrease the levels of atovaquone (Wellvone).

Strains of herpes simplex and varicella zoster virus that have developed resistance to aciclovir have been reported in immunosuppressed people.

Aciclovir comes in several different formulations. Tablets are usually used, although an intravenous form is sometimes used for treating serious herpes attacks.

Aciclovir cream, which is available without prescription, is licensed for treating or preventing cold sores (herpes simplex blisters on the lips). The cream should not be used for treating herpes elsewhere in the body. A different ointment formulation is available for treating herpes simplex infections of the eye.

Aciclovir tablets are available on prescription, but intravenous aciclovir is used within hospital settings only.