Antiviral Drugs: Mechanism of Action and Adverse Effects Quiz

Interferons

• Interferons are naturally occurring glycoproteins that can be synthesized using recombinant DNA technology and administered IV
• Interferon alpha is used to treat chronic hepatitis B/C, genital warts caused by HPV, hairy cell leukemia, and Kaposi sarcoma
• Interferon beta is used to treat relapsing-remitting multiple sclerosis
• Interferon gamma is used to treat chronic granulomatous disease

Adverse Effects of Interferons

• Influenza-like symptoms: fever, lethargy, headache, myalgia
• Bone marrow depression
• Cardiovascular problems: congestive heart failure
• Acute hypersensitivity reactions
• Hepatic failure and pulmonary infiltrates (rare)

Sofosbuvir (Sovaldi)

• Mechanism of action: inhibits RNA polymerase, incorporated into HCV RNA by NS5B polymerase, and acts as a chain terminator
• Spectrum: chronic hepatitis C virus in combination with pegylated interferon and ribavirin or with ribavirin alone for 6 months
• Adverse effects: fatigue, headache, nausea, rash, irritability

Antiviral Medications

Acyclovir

• Mechanism of action: inhibits viral DNA polymerase
• Resistance: altered or deficient thymidine kinase or DNA polymerase
• Adverse effects: depend on route of administration (local irritation, nausea, vomiting, diarrhea, headache, renal failure)

Gancyclovir

• Mechanism of action: same as acyclovir
• Resistance: cytomegalovirus is deficient in thymidine kinase but forms the drug by another route
• Adverse effects: severe and dose-dependent neutropenia, carcinogenic, teratogenic, and embryotoxic

Famcyclovir

• Mechanism of action: same as acyclovir (active form is penciclovir)
• Spectrum: approved only orally for the treatment of acute herpes zoster
• Adverse effects: headache, nausea, mammary adenocarcinoma, and testicular toxicity

Foscarnet

• Mechanism of action: reversibly inhibits DNA/RNA polymerases
• Spectrum: only in cytomegalic rhinitis in HIV patients
• Resistance: mutation in polymerase structure
• Adverse effects: nephrotoxicity, anemia, fever, hypo K/MG/CA/PO4, seizures, and arrhythmia

Vidarabine

• Mechanism of action: inhibits viral DNA synthesis
• Spectrum: herpes simplex encephalitis (penetrates blood-brain barrier) and herpes simplex keratoconjunctivitis (as an ointment)
• Resistance: altered DNA polymerase
• Adverse effects: short-term CNS side effects and fluid overload

AIDS Treatment

Zidovudine

• Mechanism of action: inhibits viral reverse transcriptase

Test your knowledge on antiviral drugs such as Acyclovir and Ganciclovir by understanding their mechanism of action, resistance mechanisms, and adverse effects based on different routes of administration. Explore how these drugs inhibit viral DNA polymerase and the implications of altered or deficient thymidine kinase or DNA polymerase.