Side Effects of Oseltamivir (Tamiflu)
Oseltamivir commonly causes gastrointestinal side effects, particularly nausea and vomiting, which occur in 5-15% of recipients but are usually mild and can be minimized by taking the medication with food. 1
Common Side Effects
Gastrointestinal Effects
- Nausea: Occurs in approximately 10% of adults (compared to 6% with placebo) 1
- Vomiting: Occurs in approximately 9% of adults (compared to 3% with placebo) 1
- In children, vomiting occurs in 14% (compared to 8.5% with placebo) 1
- Abdominal pain
- Dyspepsia
- Diarrhea
Taking oseltamivir with food can reduce the severity of gastrointestinal side effects 1. These symptoms are typically mild and transient, rarely leading to discontinuation of the medication 1.
Neurological Effects
- Headache
- Fatigue
- Insomnia
- Dizziness
Other Common Side Effects
- Conjunctivitis
- Nose bleed
- Rash
- Ear disorders
Rare Side Effects
- Hypersensitivity reactions 1
- Transient neuropsychiatric events: Including self-injury or delirium, reported mainly in Japanese adolescents and adults 1
Very Rare Side Effects
- Hepatitis
- Stevens-Johnson syndrome 1
Special Populations
Renal Impairment
- Oseltamivir requires dose reduction in patients with low creatinine clearance (<30 ml/min) 1
- The drug is eliminated primarily through renal excretion 2
Elderly Patients
- Elderly patients may have increased exposure to the active metabolite (approximately 25% higher) 2
- Neuropsychiatric events have been reported in elderly patients with mild neurocognitive disorders 3
Children
- Safety data for children under 1 year is limited 1
- Careful attention to dosing is essential in young children 1
Monitoring and Precautions
- Monitor patients, especially children and adolescents, for abnormal behavior during treatment 1
- Serious adverse events should be reported to FDA's MedWatch program 1
- Patients with underlying respiratory disease should be monitored closely, though zanamivir (not oseltamivir) is the neuraminidase inhibitor associated with bronchospasm 1
Pharmacokinetic Considerations
- Oseltamivir is a prodrug that is converted to its active form (oseltamivir carboxylate) in the liver 2
- Approximately 80% of orally administered oseltamivir is absorbed systemically 1
- The active metabolite has a half-life of 6-10 hours 1
While oseltamivir is generally well-tolerated, healthcare providers should be aware of the potential side effects, particularly gastrointestinal symptoms, and advise patients accordingly. Taking the medication with food can help minimize these effects.