Antiviral Drugs

Classification of viral infections Herpes simplex and varicella-zoster Human immunodeficiency Influenza A Cytomegalovirus Respiratory Syncytial virus (RSV) Drugs that modulate the host immune system

Herpes simplex and varicella-zoster Aciclovir Valaciclovir famciclovir

Aciclovir Mechanism of action Inhibits viral DNA synthesis only after phosphorylation by virus-specific thymidine kinase. The phosphorylated aciclovir inhibits DNA polymerase in the virus and so prevents virus DNA formation

Aciclovir It is effective against susceptible Herpes viruses if started early in the course of infection, but it does not eradicate persistent infection because viral DNA is integrated in the host genome.

Aciclovir Clinical uses Herpes simplex virus Skin infections, including initial and recurrent labial and genital herpes Ocular keratitis Encephalitis, disseminated disease (IV)

Aciclovir (clinical uses) Varicella-zoster virus Chickenpox, particularly in the immunocompromised (IV) or in the immunocompetent with pneumonitis or hepatitis (IV) Shingles in immunocompetent persons

Aciclovir Adverse effects Ophthalmic ointment causes a mild transient stinging sensation gastrointestinal symptoms, headache, and neuropsychiatric reactions.

Human immunodeficiency Nucleoside reverse transcriptase inhibitors Protease inhibitors Non- nucleoside reverse transcriptase inhibitors Entry inhibitor

Nucleoside reverse transcriptase inhibitors Zidovudine (Retrovir) Didanosine Lamivudine

Zidovudine (Retrovir) Mechanism of action Has a high affinity for HIV’s reverse transcriptase and is integrated by it into the viral DNA chain causing premature chain termination. The drug must be present continuously.

Zidovudine (Retrovir) Clinical uses Serious manifestations of HIV infection in patients with acquired immunodeficiency syndrome or AIDs related complex

Zidovudine (Retrovir) Adverse effects Anorexia, nausea, vomiting, Headache, dizziness, Malaise and myalgia Anemia and neutropenia Hepatic necrosis

Protease inhibitors (amprenavir) Mechanism of action In its process of replication, HIV produces protein and also a protease, which cleaves the protein into component parts that are subsequently reassembled into virus particles; protease inhibitors disrupt this essential process

Protease inhibitors Adverse effects GIT disturbance, headache, dizziness, sleep disturbance, pancreatitis, neutropenia, and rashes.

Non-nucleoside reverse transcriptase Used in africa HIV1 Efavirenz

Entry inhibitor Enfuvirtide is the first antiretroviral agent to target the host cell attachment/entry stage in the HIV replicaton cycle.

Influenza A Amantadine Zanamivir Oseltamivir (Tamiflu)

Amantadine Is only effective only against influenza A; it acts by interfering with the uncoating and release of viral genome into the host cell.

Amantadine Clinical Uses Used orally for the prevention and treatment of infection with influenza A virus Adverse effects Dizziness, nervousness, and insomnia

Zanamivir Is a viral neuraminidase inhibitor that blocks both entry of influenza A and B viruses to target cells.

Oseltamivir (Tamiflu) Is an oral pro-drug of a viral neuraminidase inhibitor. it reduces the severity and duration of symptoms caused by influenza A or B Is one option for treatment and prophylaxis of avian H5N1 influenza

Cytomegalovirus Ganciclovir Resembles aciclovir in its mode of action, but is much more toxic

Respiratory syncytial virus (RSV) Ribavirin is a synthetic nucleoside used for RSV bronchiolitis in infants and children, inhaled by a special ventilator.

Drugs that modulate the host immune system Interferons Directly on uninfected cells to induce enzymes that degrade viral RNA Indirectly by stimulating the immune system To modify cell regulator mechanisms and inhibit neoplastic growth

Drugs that modulate the host immune system Interferons Interferons are cassified as alfa, beta, gamma according to their antigenic and physical properties. Interferon alfa 2 a and 2b also improve the manifestations of viral hepatitis. Adverse effects Are common and include an influenza-like syndrome

Drugs that modulate the host immune system Imiquimod is used topically for genital warts (caused by papillomaviruses). Treatment for 2-3 months results in gradual clearance of warts in about 50% patients.