Notes on Anti-Influenza Drugs, Pharmacological effects, Pharmacokinetics by Chart and MCQ for GPAT, NEETPG, NORCET Exams
Anti-Influenza Drugs
1. Classification
| Class | Drugs |
|---|---|
| M2 Ion Channel Inhibitors | Amantadine, Rimantadine |
| Neuraminidase Inhibitors | Oseltamivir, Zanamivir, Peramivir |
| Cap-dependent Endonuclease Inhibitors | Baloxavir marboxil |
| RNA Polymerase Inhibitors (Investigational) | Favipiravir |
2. Mechanism of Action
-
M2 Inhibitors (Amantadine, Rimantadine): Block M2 proton channel → prevent uncoating of viral RNA in host cells.
-
Neuraminidase Inhibitors: Inhibit neuraminidase enzyme → prevent viral release from host cell.
-
Baloxavir Marboxil: Inhibits cap-dependent endonuclease → blocks viral mRNA transcription.
-
Favipiravir: Inhibits RNA-dependent RNA polymerase → inhibits viral replication.
3. Pharmacology & Side Effects
| Drug | Route | Common Side Effects | Severe Side Effects |
|---|---|---|---|
| Amantadine | Oral | Nausea, insomnia | Hallucination, orthostatic hypotension |
| Oseltamivir | Oral | GI upset | Neuropsychiatric effects (esp. in children) |
| Zanamivir | Inhalation | Cough, bronchospasm | Not recommended in asthma/COPD |
| Peramivir | IV | Diarrhea | Rare neuropsychiatric events |
| Baloxavir | Oral | Diarrhea, bronchitis | Hypersensitivity (rare) |
4. Drug-Drug Interactions
-
Amantadine: Interacts with CNS stimulants, anticholinergics → additive side effects.
-
Oseltamivir: Minimal interactions.
-
Zanamivir: Avoid in respiratory disease patients.
-
Baloxavir: Chelation with polyvalent cations (Ca++, Fe++, Mg++) → reduced absorption.
5. Pharmacokinetic Parameters Chart
| Drug | Absorption | Half-Life (t½) | Metabolism | Excretion | Notes |
|---|---|---|---|---|---|
| Amantadine | Good (oral) | 15–20 hrs | Minimal | Renal | Adjust dose in renal impairment |
| Oseltamivir | Prodrug, good oral | 6–10 hrs | Hepatic (to active carboxylate) | Renal | Start within 48h of symptoms |
| Zanamivir | Poor oral (inhaled) | 2.5–5 hrs | None | Renal | Caution in asthma |
| Peramivir | IV only | ~20 hrs | Minimal | Renal | Single-dose therapy possible |
| Baloxavir | Oral, rapid | ~80 hrs | Hepatic (UGT1A3) | Fecal | Long half-life, single dose |
MCQs on Anti-Influenza Drugs
1. Which of the following is a neuraminidase inhibitor?
A. Amantadine
B. Oseltamivir
C. Baloxavir
D. Favipiravir
Answer: B. Oseltamivir
2. What is the mechanism of action of baloxavir & marboxil?
A. M2 ion channel blocker
B. Neuraminidase inhibitor
C. Cap-dependent endonuclease inhibitor
D. RNA polymerase inhibitor Answer: C. Cap-dependent endonuclease inhibitor
3. Zanamivir is contraindicated in which condition?
A. Hypertension
B. Asthma
C. Diabetes
D. Renal failure Answer: B. Asthma
4. Which of the following drugs shows chelation interaction with antacids?
A. Oseltamivir
B. Baloxavir
C. Peramivir
D. Zanamivir Answer: B. Baloxavir
5. Which anti-influenza drug is administered via the inhalation route?
A. Oseltamivir
B. Amantadine
C. Zanamivir
D. Baloxavir Answer: C. Zanamivir