Antiviral Agents for Influenza A

Antiviral Agents Overview

• Antiviral agents like Rimantadine, Acyclovir, Nevirapine, Zidovudine, Fosamprenavir, Enfuvirtide, Maraviroc, Raltegravir, Adefovir, and Simeprevir target various viral infections, primarily influenza, herpes, and HIV.

Rimantadine

• Therapeutic action: Inhibits viral replication by preventing virus uncoating.
• Indicated for prophylaxis and treatment of influenza A in adults and children.
• Pharmacokinetics: Oral administration, slow onset, peak effect at 6 hours, half-life of 25.4 hours; excreted unchanged in urine.
• Contraindications: Embryotoxic; avoid during pregnancy and lactation.
• Adverse effects: Light-headedness, dizziness, insomnia, nausea, and depression.
• Drug interactions: Increases atropine-like effects with anticholinergics; may reduce effectiveness of aspirin and acetaminophen.

Acyclovir

• Therapeutic action: Inhibits viral DNA replication with minimal impact on human cells.
• Indications: Effective against herpes simplex, herpes zoster, and cytomegalovirus (CMV), especially in immunocompromised patients.
• Pharmacokinetics: Oral (varying onset, peak in 1.5-2 hours), IV (immediate onset, peak in 1 hour), topical (not absorbed systemically), half-life of 2.5-5 hours; excreted unchanged in urine.
• Contraindications: Use cautiously in pregnancy and lactation; caution in patients with allergies and renal disease.
• Adverse effects: Headache, vertigo, nausea, vomiting, rash.
• Drug interactions: Increased risk of nephrotoxicity with nephrotoxic drugs; drowsiness risk with zidovudine.

Nevirapine

• Therapeutic action: Binds to HIV-1 reverse transcriptase, blocking replication.
• Indications: For HIV-1 infected patients with clinical or immunological deterioration, used with other retrovirals.
• Pharmacokinetics: Oral, rapid onset, peak in 4 hours, half-life of 45 hours; metabolized in liver, excreted in urine.
• Contraindications: Limited pregnancy studies; not recommended for breastfeeding or children.
• Adverse effects: Headache, nausea, liver dysfunction, rash.
• Drug interactions: Avoid with hormonal contraceptives and protease inhibitors.

Zidovudine

• Therapeutic action: Thymidine analogue that inhibits replication of retroviruses like HIV.
• Indications: Managing symptomatic HIV infection in adults and preventing maternal-fetal transmission.
• Pharmacokinetics: Oral (peak in 30-90 mins), IV (peak at infusion end), half-life of 30-60 mins; metabolized in liver, excreted in urine.
• Contraindications: Only proven safe agent during pregnancy; caution in bone marrow suppression, hepatic/renal impairment.
• Adverse effects: Headache, insomnia, diarrhea, bone marrow suppression.
• Drug interactions: Severe drowsiness when combined with cyclosporine.

Fosamprenavir

• Therapeutic action: Inhibits protease activity, resulting in noninfectious virus particles.
• Indications: Managing symptomatic HIV infection in adults.
• Pharmacokinetics: Oral, varying onset, peak in 1.5-4 hours, half-life of 7.7 hours; metabolized in liver, excreted in feces and urine.
• Contraindications: Caution in pregnancy; avoid breastfeeding with HIV patients.
• Adverse effects: Headache, mood changes, rash, potential for stevens-johnson syndrome.
• Drug interactions: Increased risk of adverse effects if combined with ritonavir.

Enfuvirtide

• Therapeutic action: Prevents HIV-1 entry into cells by inhibiting viral membrane fusion.
• Indications: HIV-1 patients with clinical or immunological deterioration after other treatments.
• Pharmacokinetics: Subcutaneous, slow onset; peak in 4-8 hours, half-life of 3.2-4.4 hours; metabolized in liver.
• Contraindications: Hypersensitivity and nursing mothers; caution in lung disease or pregnancy.
• Adverse effects: Insomnia, peripheral neuropathy, pneumonia.
• Drug interactions: No reported interactions, but caution with other drugs.

Maraviroc

• Therapeutic action: Binds to CCR5 on cell membranes, preventing HIV-1 entry.
• Indications: Combination therapy for adults with CCR5 tropic HIV-1.
• Pharmacokinetics: Oral, peak in 0.5-4 hours, half-life of 14-28 hours; metabolized in liver, excreted in feces and urine.
• Contraindications: Hypersensitivity; not approved for children; caution in liver disease and pregnancy.
• Adverse effects: Severe hepatotoxicity, dizziness, gastrointestinal symptoms.
• Drug interactions: Increased toxicity with CYP3A inhibitors; decreased effectiveness with CYP3A inducers.

Raltegravir

• Therapeutic action: Inhibits integrase, preventing HIV-1 provirus formation.
• Indications: Patients with evidence of viral replication.
• Pharmacokinetics: Oral, rapid onset, peak in 3 hours, half-life of 9 hours; metabolized in liver.
• Contraindications: Hypersensitivity, not for initial treatment in adults or nursing mothers; caution for rhabdomyolysis risk.
• Adverse effects: Headache, dizziness, muscle risks.
• Drug interactions: Monitor if combined with rifampin; avoid St. John’s wort.

Adefovir

• Therapeutic action: Inhibits reverse transcriptase in hepatitis B virus, leading to viral replication inhibition.
• Indications: Chronic hepatitis B treatment in adults with active disease.
• Pharmacokinetics: Oral, rapid onset, peak in 0.6-4 hours; half-life of 7.5 hours; excreted in urine.
• Contraindications: Known allergies, lactation, caution in renal/liver impairment.
• Adverse effects: Headache, nausea, potential hepatomegaly.
• Drug interactions: Increased renal toxicity risk with other nephrotoxic drugs.

Simeprevir

• Therapeutic action: Inhibits hepatitis C protease formation, preventing viral replication.
• Indications: Chronic hepatitis C in adults with compensated liver dysfunction.
• Pharmacokinetics: Oral, rapid onset, peak in 4-6 hours, half-life of 10-12 hours; excreted in feces.
• Contraindications: Known allergies, pregnancy, caution in severe liver disease.
• Adverse effects: Fatigue, gastrointestinal issues, rash.
• Drug interactions: Caution with other protease inhibitors; avoid St. John's wort for efficacy.