What are the adverse reactions to oseltamivir (Tamiflu) in a 13‑month‑old child?

Adverse Reactions to Oseltamivir (Tamiflu) in a 13-Month-Old Child

Vomiting is the most common adverse reaction in young children taking oseltamivir, occurring in approximately 9-16% of treated infants and toddlers, but it is typically mild, transient, and rarely leads to discontinuation of therapy. 1, 2, 3

Most Common Adverse Effects in Infants and Young Children

Gastrointestinal Reactions

• Vomiting is the predominant adverse effect, reported in 9-16% of children aged 1-12 years receiving oseltamivir compared to 8-9% receiving placebo 1, 3
• Diarrhea occurs in approximately 7% of infants under 1 year of age 1, 2, 3
• Diaper rash was reported in 7% of infants 2 weeks to less than 1 year of age in clinical trials 3
• These gastrointestinal symptoms typically appear within the first 1-2 days of treatment and resolve spontaneously within 1-2 days 3, 4

Strategies to Minimize Gastrointestinal Side Effects

• Administering oseltamivir with food or a light snack significantly reduces nausea and vomiting without affecting antiviral efficacy 2, 5, 4, 6
• Taking the medication with meals improves gastrointestinal tolerability and should be emphasized to caregivers 2, 5

Serious Adverse Reactions (Rare)

Neuropsychiatric Events

• Post-marketing surveillance has identified rare cases of abnormal behavior, delirium, hallucinations, agitation, anxiety, confusion, and nightmares, primarily in pediatric and adolescent patients 3
• However, extensive reviews of controlled clinical trial data and ongoing surveillance have failed to establish a causal link between oseltamivir and neuropsychiatric events 1, 2
• Influenza infection itself is strongly associated with neurologic and behavioral symptoms, making it difficult to attribute these events specifically to the medication 2

Hypersensitivity and Skin Reactions

• Serious skin reactions including toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme have been reported in post-marketing surveillance, though causality has not been definitively established 3
• Rash, dermatitis, urticaria, and eczema have been reported but are uncommon 3
• Anaphylactic/anaphylactoid reactions and swelling of the face or tongue are rare but serious hypersensitivity reactions 3

Dosing for a 13-Month-Old Child

Weight-Based Dosing

• For children ≥12 months weighing ≤15 kg: 30 mg (5 mL of 6 mg/mL suspension) twice daily for 5 days 1, 2
• For children ≥12 months weighing >15-23 kg: 45 mg (7.5 mL) twice daily for 5 days 1, 2
• Use the oral suspension formulation (6 mg/mL concentration) with a calibrated oral syringe for accurate dosing 2, 5

Safety Profile and Discontinuation Rates

• Only approximately 1% of patients discontinue oseltamivir due to adverse effects in clinical trials, indicating that side effects are generally manageable 5, 3
• The safety profile in infants 2 weeks to less than 1 year of age was generally comparable to that observed in older pediatric and adult subjects 3
• Oseltamivir is FDA-approved for treatment in children as young as 2 weeks of age, and the American Academy of Pediatrics supports its use in both term and preterm infants from birth when benefits outweigh risks 1, 2

Important Clinical Caveats

• Do not withhold treatment due to concerns about vomiting alone—the clinical benefits of reducing illness duration (by approximately 17.6-36 hours) and preventing complications (34% reduction in otitis media risk) outweigh the transient gastrointestinal side effects 1, 2
• Monitor for signs of dehydration if vomiting occurs, especially in young infants who may be more vulnerable 2
• Caregivers should be counseled that gastrointestinal symptoms are expected, mild, and self-limited in most cases 1, 3, 4
• Serious adverse reactions are rare, and the overall safety profile supports the use of oseltamivir in high-risk populations including children under 2 years of age 1, 2, 3