Oseltamivir

# Oseltamivir ## Overview - **Classification**: Antiviral, Neuraminidase Inhibitor - **Mechanism**: Selectively inhibits influenza A and B virus neuraminidase, preventing viral release from infected cells and reducing viral spread. ## Primary Indications 1. **Treatment of Influenza**: Acute, uncomplicated influenza A and B. 2. **Prophylaxis of Influenza**: Post-exposure or seasonal prophylaxis during an influenza outbreak. ## Adult Dosing ### Standard Dosing **Influenza Treatment** - **Dose**: **75 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral - **Duration**: 5 days - **Special Considerations**: Initiate within **48 hours** of symptom onset. **Influenza Prophylaxis** - **Dose**: **75 mg** - **Frequency**: Once daily (QD) - **Route**: Oral - **Duration**: At least 7-10 days after exposure or for up to 6 weeks for community outbreaks. - **Special Considerations**: Initiate within **48 hours** of exposure. ### Dose Adjustments - **Renal Impairment**: - CrCl **>30 mL/min**: No adjustment needed. - CrCl **10-30 mL/min**: - Treatment: **30 mg** QD. - Prophylaxis: **30 mg** every other day. - CrCl **<10 mL/min**: Not recommended (data limited). - Hemodialysis: **30 mg** after each dialysis session (treatment), or **30 mg** once weekly (prophylaxis). - Peritoneal Dialysis: **30 mg** single dose (treatment), or **30 mg** once weekly (prophylaxis). - **Hepatic Impairment**: No adjustment required. - **Elderly Patients**: No specific adjustment, but monitor renal function. ## Pediatric Dosing ### Neonates (0-28 days) - **Influenza Treatment (Oral suspension)**: - **Dose**: **3 mg/kg** - **Frequency**: Twice daily (BID) - **Maximum**: Not specified, but adhere to mg/kg dose. - **Special Notes**: Dosing is weight-based for full-term neonates. Limited data for premature infants. - **Influenza Prophylaxis (Oral suspension)**: - **Dose**: **3 mg/kg** - **Frequency**: Once daily (QD) - **Maximum**: Not specified. - **Special Notes**: Generally not recommended due to limited data, consider on a case-by-case basis. ### Infants (1-12 months) - **Influenza Treatment (Oral suspension)**: - **Dose**: **3 mg/kg** - **Frequency**: Twice daily (BID) - **Maximum**: No specific max, but do not exceed adult single dose of **75 mg**. - **Duration**: 5 days. - **Influenza Prophylaxis (Oral suspension)**: - **Dose**: **3 mg/kg** - **Frequency**: Once daily (QD) - **Maximum**: No specific max, but do not exceed adult single dose of **75 mg**. - **Duration**: 7-10 days. ### Children (1-12 years) - **Influenza Treatment (Capsules or Oral suspension)**: - Weight ≤15 kg: **30 mg** BID - Weight >15 to 23 kg: **45 mg** BID - Weight >23 to 40 kg: **60 mg** BID - Weight >40 kg: **75 mg** BID - **Frequency**: Twice daily (BID) - **Duration**: 5 days - **Maximum**: Adult dose equivalent for weight >40 kg. - **Influenza Prophylaxis (Capsules or Oral suspension)**: - Weight ≤15 kg: **30 mg** QD - Weight >15 to 23 kg: **45 mg** QD - Weight >23 to 40 kg: **60 mg** QD - Weight >40 kg: **75 mg** QD - **Frequency**: Once daily (QD) - **Duration**: 7-10 days - **Maximum**: Adult dose equivalent for weight >40 kg. ### Adolescents (13-18 years) - **Dose**: Adult dosing guidelines apply. - **Maximum**: **75 mg** BID for treatment, **75 mg** QD for prophylaxis. ## Safety Information ### Contraindications - **Absolute**: Known serious hypersensitivity to oseltamivir or any component of the formulation. ### Common Adverse Effects - **Very Common (>10%)**: Nausea, Vomiting (especially with first dose). - **Common (1-10%)**: Diarrhea, Headache, Abdominal pain. - **Serious but Rare**: Neuropsychiatric events (delirium, hallucinations, self-injury) mainly in pediatric patients, Stevens-Johnson syndrome, Toxic Epidermal Necrolysis. ### Key Drug Interactions - **Live Attenuated Influenza Vaccine (LAIV)**: Avoid administration for **2 weeks** before and **48 hours** after oseltamivir use. - **Probenecid**: May increase oseltamivir exposure (minor clinical significance, typically no dose adjustment). - **Other drugs eliminated by renal tubular secretion**: Co-administration may affect plasma concentrations. ## Monitoring & Follow-up - **Before Treatment**: Assess baseline renal function (CrCl). - **During Treatment**: Monitor for symptom improvement or worsening of influenza. - **Clinical Signs**: Watch for unusual behavior, confusion, or sudden mood changes, particularly in children and adolescents. ## Clinical Pearls - 💡 **Early Initiation**: Treatment is most effective when initiated within **48 hours** of symptom onset. - 💡 **Take with Food**: Administer with food to reduce nausea and vomiting. - 💡 **Complete Course**: Patients should complete the full prescribed course, even if symptoms improve. - 💡 **Neuropsychiatric Risk**: Counsel patients/caregivers on the rare risk of neuropsychiatric events; seek immediate medical attention if observed. - 💡 **Not a Vaccine Substitute**: Oseltamivir does not replace influenza vaccination. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.