Side Effects of Tamiflu (Oseltamivir)
Tamiflu (oseltamivir) commonly causes gastrointestinal side effects, particularly nausea and vomiting, which 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) 2, 1
- Vomiting: Occurs in approximately 9% of adults (compared to 3% with placebo) and 14% of children (compared to 8.5% with placebo) 2
- Diarrhea: Reported in <5% of patients 2
- Taking oseltamivir with food can reduce the severity of these gastrointestinal side effects 2, 1
- Approximately 1% of patients discontinue the medication due to gastrointestinal side effects 2
Other Common Side Effects (each reported by <5% of patients)
- Headache
- Dizziness
- Sinusitis
- Nasal symptoms
- Bronchitis
- Cough
- Ear, nose, and throat infections 2
Serious Side Effects
Neuropsychiatric Events
- Transient neuropsychiatric events (self-injury or delirium) have been reported, particularly among adolescents and adults in Japan 2, 3
- The FDA advises monitoring patients, especially children and adolescents, for abnormal behavior during treatment 2, 4
- Several analyses have found that oseltamivir is not associated with an increased risk for neuropsychiatric events 2
- Research suggests these effects may be related to increased dopamine levels in the brain 5
Allergic Reactions
- Serious skin and allergic reactions can occur 4
- Stop taking oseltamivir and seek medical help immediately if you experience:
- Skin rash or hives
- Blisters or peeling skin
- Mouth sores
- Itching
- Facial swelling
- Breathing difficulties
- Chest pain or tightness 4
Special Populations
Respiratory Disease
- Unlike zanamivir (another influenza antiviral), oseltamivir does not have specific warnings against use in patients with underlying respiratory disease 2
Pregnancy
- Oseltamivir is a "Pregnancy Category C" medication
- Should be used during pregnancy only if potential benefit justifies potential risk to the fetus
- No adverse effects have been reported among women who received oseltamivir during pregnancy or among infants born to such women 2
Children
- Limited safety data exists for children under 1 year of age
- Careful attention to dosing is essential in young children 2, 1
Drug Interactions
- Limited clinical data regarding drug interactions
- Oseltamivir is excreted in the urine by glomerular filtration and tubular secretion via the anionic pathway
- Potential for interaction with other drugs excreted by this pathway
- Coadministration with probenecid results in reduced clearance of oseltamivir carboxylate by approximately 50% and a corresponding twofold increase in plasma levels 2
Practical Considerations
- Side effects are generally mild and transient 6
- In outbreak settings, mass prophylaxis with oseltamivir has shown higher rates of adverse effects and non-completion of therapy (up to 41% of recipients reporting side effects) 7
- Taking oseltamivir with a light snack can reduce gastrointestinal side effects 6
- Monitor children and adolescents closely for abnormal behavior during treatment 4
Remember that despite these potential side effects, oseltamivir remains an effective treatment for influenza when initiated promptly, reducing the duration of symptomatic illness and hastening return to normal activity levels 8.