Antiviral agents famciclovir

Famciclovir is an orally administered prodrug of the antiviral agent penciclovir. Famciclovir is indicated for the treatment of acute herpes zoster (shingles), treatment or suppression of recurrent genital herpes in immunocompetent patients, treatment of recurrent mucocutaneous herpes simplex infections in HIV-infected patients. 

Detailed pharmacology of acyclovir, valacyclovir, penciclovir and famciclovir is discussed in detail in chapter Chemotherapeutic agents- Antiviral agents. ... 

There are now many other DNA synthesis inhibitors in use, e.g., cidofir, idoxuridine, famciclovir, ganciclovir, and trifluorothymidine, and this class of compound makes up the majority of antiviral agents currently available or in clinical trials. However poor selectivity (and the associated toxicity) is still a key problem in this area owing to the similarities of viral and cellular metabolism (5). 

Other enzymes widely used in organic syntheses are lipases. Lipases are serine hydrolases that catalyze the hydrolysis of lipids to fatty acids. An example of their use is in the resolution of racemic methyl 4-benzyloxy-2-(hydroxymethyl)[l- C]butyrate (8), an intermediate for the carbon-13 labeling of the antiviral agents penciclovir and famciclovir. From a limited number of candidates Candida cylindracea lipase turned out to be the enzyme of choice. At optimal reaction conditions (pH 5-7, 35 °C) no nonenzymatic hydrolysis was detectable. Due to insufficient enzymatic stereospecificity, however, the hydrolysis provided the unreacted dextrorotary ester 2 at an optical purity of 94% e.e. and the hydrolyzed levorotary acid 10 at an optical purity of 70% e.e. 

Famciclovir is an ester prodmg of the antiviral dmg pen-ciclovir which is used to treat herpes. It was designed to increase the lipophilicity of pendclovir and hence improve oral absorption. It has to be administered less frequently than less lipophilic antiviral agents such adclovir. The ester groups are removed by esterases in the body. The purine ring is also oxidised in the liver to yield penddovir. 

Levatol ) is a (subtype-non-selective) P-adrenoceptor ANTAGONIST. It can be used as an antihypertensive. penbutolol sulfate penbutolol. penciclovir [ban, inn] (Vectavir ) is a synthetic nucleoside analogue antiviral, used topically as a treatment for herpes infections. It can also be used orally in the form of its prodrug famciclovir. It is active as an anti-hiv agent. Pendramine penicillamine. 

The use of trimethoprim-sulfamethoxazole in cancer patients at risk for P. jiwveci pneumonia has reduced the incidence of this protozoal infection substantially. Antiviral prophylaxis with acyclovir or newer agents (valacyclovir and famciclovir) is employed in most centers to reduce the risk of HSV reactivation in patients with acute leukemia undergoing intensive chemotherapy. Varicella vaccine provides good protection (90%) in leukemic children and also may be useful in seronegative adults, although the vaccine has been less well studied in this population. 

Famciclovir, the oral formulation of penciclovir, is a new antiherpes agent that is well absorbed following oral administration with little intersubject variability, and is rapidly converted to penciclovir with a bioavailability of 77%. Furthermore, although the activities of penciclovir and acyclovir against varicella-zoster virus (VZV) in infected cell lines appear to be comparable, penciclovir-triphosphate persists in virus-infected cells far longer than acyclovir-triphosphate, resulting in more prolonged antiviral activity. The intracellular half-life of penciclovir-triphosphate in VZV-infected cells is reported to be 9 hours, whereas that of... 

MECHANISMS OE ACTION AND RESISTANCE Lamivudine triphosphate potently inhibits the DNA polymerase/reverse transcriptase of HBV. Lamivudine has enhanced antiviral activity against hepadnaviruses when combined with adefovir or penciclovir. Point mutations in the HBV DNA polymerase markedly reduce sensitivity. Lamivudine resistance confers cross-resistance to agents such as emtricitabine and is often associated with an additional mutation that confers cross-resistance to famciclovir. Lamivudine-resistant HBV retains susceptibility to adefovir and partially to entecavir. Viruses bearing certain mutations are less replication competent than wild-type HBV, but lamivudine resistance is associated with elevated HBV DNA levels, decreased likelihood of HbeAg loss or seroconversion, hepatitis exacerbations, and progressive fibrosis and graft loss in transplant recipients. 

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