Denavir (penciclovir)

Penciclovir, a synthetic acyclic guanine nucleoside analog, is an antiviral agent active against various Herpesviridae, including herpes simplex virus types 1 and 2 (HSV-1 and HSV-2).

Penciclovir, a synthetic acyclic guanine nucleoside analog, is an antiviral agent. Penciclovir is structurally and pharmacologically related to acyclovir.

Penciclovir is converted in vivo to a pharmacologically active triphosphate metabolite, which has in vitro and in vivo inhibitory activity against various Herpesviridae, including herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) and varicella-zoster virus (VZV). The drug also has some in vitro activity against Epstein-Barr virus (EBV), but only limited activity in vitro against cytomegalovirus (CMV).

Penciclovir triphosphate exerts its antiviral effects on HSV and VZV by interfering with DNA synthesis and inhibiting viral replication. In virus-infected cells, penciclovir is converted to penciclovir monophosphate by viral thymidine kinase; the monophosphate is further converted to the diphosphate via cellular kinase and then to the triphosphate via other cellular enzymes. Penciclovir triphosphate is a viral DNA polymerase inhibitor and stops replication of viral DNA by competing with deoxyguanosine triphosphate for viral DNA polymerase and inhibiting viral DNA chain elongation.

The inhibitory activity of penciclovir triphosphate is highly selective because of the drug's affinity for thymidine kinase encoded by HSV and VZV. The mechanism of action of penciclovir is similar to that of acyclovir. Although penciclovir has a higher affinity for HSV thymidine kinase than acyclovir and penciclovir triphosphate is more stable than acyclovir triphosphate in HSV-infected cells, HSV DNA polymerases have a higher affinity for acyclovir triphosphate than for penciclovir triphosphate and the net effect is that these nucleoside analogs have similar antiviral potencies.

Although most HSV isolates tested have been susceptible to penciclovir in vitro and intermittent topical use of the drug does not appear to be associated with emergence of penciclovir resistance, HSV resistant to penciclovir have been produced in vitro and penciclovir-resistant clinical isolates have been reported rarely. HSV clinical isolates resistant to acyclovir because they are deficient in viral thymidine kinase (i.e., thymidine kinase-negative mutants) generally are cross-resistant to penciclovir. However, some viral thymidine kinase- or DNA polymerase-altered strains that are resistant to acyclovir have been susceptible to penciclovir in vitro.

For the topical treatment of herpes labialis, penciclovir is commercially available as a 1% cream. Each gram of the white cream contains 10 mg of penciclovir and cetostearyl alcohol, mineral oil, polyoxyl 20 cetostearyl ether, propylene glycol, purified water, and white petrolatum. Following topical application of penciclovir to skin, the drug is not appreciably absorbed into systemic circulation, even at single or multiple dosages up to 180 mg daily (approximately 67 times the estimated usual topical dosage).

Penciclovir has limited oral bioavailability (about 5%). A prodrug of penciclovir, famciclovir, is commercially available for oral use. (See Famciclovir 8:18.32.)

USES: This medication is used to treat "cold sores/fever blisters" (herpes labialis). It can speed up healing of the sores and decrease symptoms (such as tingling, pain, burning, itching). Penciclovir belongs to a class of medications known as antivirals.

It works by stopping the growth of the virus. This medication does not cure herpes, and it does not prevent passing the infection to someone else. It does not prevent future occurrences.

Generic name: penciclovir
Pronunciation: (pen-SYE-kloe-vir)
Drug class: Topical Antivirals
Therapeutic class: Dermatological

The following indications are listed for Denavir:

• Herpes Labialis

Also known as: Herpes Simplex Type 1 Infection Of The Lip Or Nares, Hsv Type 1 Infection Of The Lip Or Nares.