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Anti-viral drugs

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When is anti-viral therapy most important? 3 things
severe disease, immunocompromised patient, latent disease
What are the two uncoating inhibitors?
Amantadine and rimantadine
What is the mechanism of action for Amantadine?
Its a cyclic compount that binds to the M2 channel of influenza A. With M2 inhibited the endosome cannot be acidified and viral RNA transcriptase can't be activated.
How are amantadine and rimantadine metabolized?
Amantadine by renal excretion.
Rimatadine by hepatic metabolism
What are the adverse effects of amantadine?
CNS aniexty, insomnia, dizziness
GI nausea/vomiting
Teratogen
Which anti influenza drugs are also effective against type B influenza?
Zanamivir and osteltamivir
How do Zanamivir and osteltamivir work?
They inhibit neuroaminidase cleave sialic acid from viral proteins and surface proteins of infected cells. they prevent release and spread of mature virus particles.
How does acyclovir (ACV) work?
Gets activated to ACV TP - a competitive inhibitor of DNA pol. It lead s to chain termination. A viral thymidine kinase (TK) is needed for phosporylation.
What is ACV used for?
HSV or VZV infections. HSV-1, HSV-2, VZV are most sensitive. EBV is less sensitive and CMV is least sensitive. § Oral – mucucutaneous and genital herpes lesions. Prophylaxis in AIDS and other immunocompromised patients
ACV toxicity?
usually well tolerated, GI disturbances or headache can occur. Rapid IV infusion can produce renal dysfunction.
How is ACV selectively toxic?
acyclovir requires activation by a viral enzyme (Thymidine Kinase). Phosphorylated drug (ACV TP) actively inhibits viral DNA polymerase. Acylovir binds more strongly to viral DNA polymerase than the host polymerase.
Mechanism of viral resistance to ACV?
mutations in TK or DNAP genes, mutants are resistant to other drugs of the ACV class
How is ganciclovir different from ACV?
Ganciclovir is 100x more active than AC against CMV. · A viral specific TK phosphorylates GCV and cellular enzymes convert it to triphosphate which inhibits viral DNAP. Chain termination is minimal
Uses of GCV?
CMV prophylaxis, and retininitis in immunocompromised or transplant recipients
Adverse effects of GCV?
bone marrow suppression (leukopenia, thrombocytopenia) mucositis, hepatic dysfunction, seizures. If used with zidovudine or other myelosuppressive agents, it may causes severe neutropenia.

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