indication

Used to treat recurrent cold sores on the lips and face from various herpesvirus invections.

pharmacology

Penciclovir is the active metabolite of the oral product famciclovir. The more favorable results observed with topical penciclovir versus topical acyclovir for the treatment of herpes labialis may be due to the longer intracellular half-life of penciclovir in HSV-infected cells. The activated drug inhibits the viral DNA polymerase. This impairs the ability of the virus to replicate within the cell.

mechanism of action

Penciclovir has in vitro activity against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2). In cells infected with HSV-1 or HSV-2, viral thymidine kinase phosphorylates penciclovir to a monophosphate form. The monophosphate form of the drug is then converted to penciclovir triphosphate by cellular kinases. The intracellular triphosphate of penciclovir is retained in vitro inside HSV-infected cells for 10-20 hours, compared with 0.7-1 hour for acyclovir. in vitro studies show that penciclovir triphosphate selectively inhibits viral DNA polymerase by competing with deoxyguanosine triphosphate. Inhibition of DNA synthesis of virus-infected cells inhibits viral replication. In cells not infected with HSV, DNA synthesis is unaltered. Resistant mutants of HSV can occur from qualitative changes in viral thymidine kinase or DNA polymerase. The most commonly encountered acyclovir-resistant mutants that are deficient in viral thymidine kinase are also resistant to penciclovir.

toxicity

Symptoms of overdose include headache, abdominal pain, increased serum lipase, nausea, dyspepsia, dizziness, and hyperbilirubinemia.

biotransformation

Hepatic

absorption

Measurable penciclovir concentrations were not detected in plasma or urine of healthy male volunteers (n= 12) following single or repeat application of the 1% cream at a dose of 180 mg penciclovir daily.

half life

2 hours

drug interactions

Aluminium: The multivalent agent decreases the effect of penicillamine

Attapulgite: The multivalent agent decreases the effect of penicillamine

Digoxin: The multivalent agent decreases the effect of penicillamine

Iron: The multivalent agent decreases the effect of penicillamine

Kaolin: The multivalent agent decreases the effect of penicillamine