What are the potential side effects of taking Tamiflu (Oseltamivir) for a patient with a history of respiratory issues, such as asthma or COPD?

Side Effects of Tamiflu (Oseltamivir)

The most common side effects of Tamiflu are nausea and vomiting, occurring in approximately 10-14% of patients, which can be significantly reduced by taking the medication with food. 1, 2, 3

Common Gastrointestinal Side Effects

• Nausea without vomiting occurs in approximately 10% of adults and vomiting in approximately 9%, compared to 6% and 3% in placebo groups respectively 1
• Among children, 14% experience vomiting compared to 8.5% receiving placebo 1
• Taking oseltamivir with food significantly reduces these gastrointestinal symptoms without affecting drug absorption 1, 2, 3
• Only 1% of patients discontinue treatment due to nausea or vomiting 1
• Other gastrointestinal effects include diarrhea, occurring in less than 5% of patients 1

Neuropsychiatric Side Effects

• Transient neuropsychiatric events including self-injury, delirium, confusion, speech problems, shaky movements, seizures, and hallucinations have been reported, primarily in postmarketing surveillance from Japan among adolescents and adults 1, 3
• Recent analyses found that oseltamivir is not associated with an increased risk for neuropsychiatric events compared to placebo 1
• Research suggests oseltamivir increases dopamine levels in the medial prefrontal cortex, which may theoretically contribute to behavioral changes 4
• Patients and caregivers should be instructed to contact their healthcare provider immediately if confusion, speech problems, shaky movements, seizures, or hallucinations develop 3

Serious Allergic and Skin Reactions

• Serious skin and allergic reactions can occur, requiring immediate discontinuation 3
• Stop oseltamivir immediately if the following develop: skin rash or hives, skin blistering and peeling, blisters or sores in the mouth, itching, swelling of face/eyes/lips/tongue/throat, trouble breathing, or chest pain 3
• Allergic reactions including oropharyngeal or facial edema have been reported during postmarketing surveillance 1

Other Common Side Effects

• Headache occurs in less than 5% of patients in both treatment and prophylaxis studies 1, 3
• Upper respiratory symptoms including sinusitis, nasal signs and symptoms, bronchitis, cough, dizziness, and ear/nose/throat infections each occur in less than 5% of patients 1
• These symptoms occur at similar rates in placebo groups, making causality difficult to establish 1

Critical Considerations for Patients with Respiratory Disease

Oseltamivir is safe for patients with asthma or COPD, unlike zanamivir which carries significant bronchospasm risk. 5, 6

• Zanamivir (the inhaled neuraminidase inhibitor) caused a greater than 20% decline in FEV1 in 13% of patients with asthma or COPD, similar to the 14% in placebo groups, but individual cases of bronchospasm have been reported 1
• Zanamivir is not recommended for patients with underlying airway disease due to risk of serious respiratory deterioration 1
• Oseltamivir does not cause bronchospasm and is the preferred antiviral for patients with asthma or COPD 5, 6

Safety Profile Summary

• Oseltamivir has simple, uncomplicated pharmacology with no significant drug-drug interactions 7
• Electrocardiogram parameters including QT interval are unaffected even at high doses 7
• Serious adverse events occurred in 1.3% of patients receiving oseltamivir 75mg twice daily versus 1.2% in placebo recipients in clinical trials 7
• Over 4 million prescriptions have been dispensed worldwide with approximately 2,300 spontaneous reports received, most involving gastrointestinal and skin reactions 7
• A large insurance database study showed no increased risk of cardiac, neuropsychiatric, or respiratory events compared to those not receiving oseltamivir 7

Practical Management Strategies

• Always administer oseltamivir with food or a light snack to minimize nausea and vomiting 1, 2, 3
• Close observation is required when prescribing to children due to neuropsychiatric concerns 4
• If a dose is missed and it is more than 2 hours before the next scheduled dose, take it immediately; otherwise skip the missed dose 3
• Never take two doses at the same time 3