Penciclovir cream--improved topical treatment for herpes simplex infections

Abstract

Human herpesviruses can be found worldwide and cause many viral infections in immunocompetent as well as in immunocompromised patients. Herpes simplex virus (HSV) diseases can be the cause of life-threatening disease, especially in neonates. After initial infection, HSV persists latently in host neurons with the risk of periodical reactivation over a lifetime. The development of acyclovir, a potent and specific nucleoside inhibitor of the herpes DNA polymerase, was a milestone in the history of antiviral drugs in the late 1970s. During the last decades a better understanding of the replication and disease-causing state of HSV types 1 and 2 has been achieved enabling the development of new and potent antiviral compounds. In the mid-1990s, for example, valacyclovir and famciclovir were launched as prodrugs of acyclovir with improved bioavailability. Despite the numerous drugs available for the systemic treatment of HSV infections, the topical application of a cream containing an antiviral agent is still the most convenient method of treating herpes simplex labialis/facialis in the general population. For some time, the topical standard treatment for recurrent HSV infections has been acyclovir cream, despite the fact that the evidence for efficacy in recurrent episodes has been equivocal. Penciclovir, a novel acyclic nucleoside analogue, has demonstrated efficacy against HSV types 1 and 2 and seems to have a pharmacological advantage due to a prolonged half-life of its active form in HSV-infected cells. This review discusses and compares the topical treatment modalities available for HSV infections. As a conclusion, different studies are available that have shown that it is possible to reduce viral replication and hasten lesion resolution with 1% penciclovir treatment beyond the prodromal phase of the HSV infection. Comparing data of topical treatment with acyclovir and penciclovir revealed a superiority for penciclovir cream showing a significant decrease in time to lesion healing, lesion area and pain. While systemic acyclovir or valacyclovir may be valid drugs especially for HSV prophylaxis, 1% penciclovir cream should be preferred as topical treatment since there are good therapeutic results independent of the phase of development of herpetic eruptions.