What are the potential side effects of Oseltamivir (antiviral medication) in patients, particularly the elderly or those with a history of chronic health conditions such as heart disease, lung disease, or diabetes?

Oseltamivir Side Effects

The most common side effect of oseltamivir is nausea and vomiting, occurring in approximately 10% of adults and 14% of children, which is typically mild, transient, and can be reduced by taking the medication with food. 1

Gastrointestinal Side Effects

Nausea and vomiting are the predominant adverse effects:

• Adults: Nausea without vomiting occurs in approximately 10% (versus 6% with placebo), and vomiting in approximately 9% (versus 3% with placebo) 1
• Children: Vomiting occurs in 14.3% of treated children compared to 8.5% receiving placebo 1
• Only 1% of patients discontinue oseltamivir due to gastrointestinal side effects 1
• Taking oseltamivir with food significantly reduces the severity of nausea and vomiting 1
• These symptoms are typically transient, resolving within 1-2 days 2

Special Population Considerations

Elderly Patients (≥65 Years)

• No dose reduction is recommended based on age alone 1
• The standard adult dose of 75 mg twice daily remains appropriate unless renal impairment is present 1
• Elderly patients do not experience higher rates of adverse effects compared to younger adults 3

Patients with Chronic Conditions

Cardiac Disease:

• No specific cardiac adverse effects or ECG changes (including QT interval) have been observed, even at high doses 4
• Oseltamivir is safe and effective in patients with chronic heart disease 5

Pulmonary Disease:

• Unlike zanamivir (which can cause bronchospasm), oseltamivir does not cause respiratory complications in patients with asthma or COPD 1
• Oseltamivir is the preferred antiviral for patients with underlying airway disease 1

Diabetes:

• No specific adverse effects related to diabetes have been reported 4
• Standard dosing applies unless renal impairment is present 1

Renal Impairment:

• Dose reduction by 50% is required if creatinine clearance is less than 30 mL/minute 1
• Oseltamivir and its active metabolite are excreted renally, necessitating dose adjustment 1

Other Adverse Effects

Neuropsychiatric Events:

• Postmarketing surveillance has reported neuropsychiatric events, but no clear causal relationship has been established 4
• A large insurance database study showed no increased risk of neuropsychiatric events in oseltamivir users compared to non-users 4

Skin Reactions:

• Skin reactions have been reported infrequently in postmarketing surveillance 4
• A clear association between skin reactions and oseltamivir has not been established 4

Hereditary Fructose Intolerance:

• The oral suspension contains sorbitol, which may cause dyspepsia and diarrhea in patients with hereditary fructose intolerance 6

Drug Interactions

• Limited clinical data exist regarding drug interactions with oseltamivir 1
• Oseltamivir is excreted in urine by glomerular filtration and tubular secretion 1
• No clinically significant drug interactions have been identified in clinical practice 4

Safety Profile Summary

Overall tolerability is excellent:

• Serious adverse events occurred in 1.3% of oseltamivir recipients versus 1.2% of placebo recipients in clinical trials 4
• Over 4 million prescriptions have been dispensed worldwide with approximately 2,300 spontaneous adverse event reports over three winter seasons 4
• Most reports involved gastrointestinal and skin reactions 4
• No increased risk of cardiac, neuropsychiatric, or respiratory events was found in large-scale postmarketing surveillance 4

Clinical Pitfalls to Avoid

• Do not withhold oseltamivir from patients with chronic respiratory disease due to concerns about respiratory side effects—unlike zanamivir, oseltamivir does not cause bronchospasm 1
• Always adjust dose for renal impairment (creatinine clearance <30 mL/minute requires 50% dose reduction) 1
• Advise patients to take oseltamivir with food to minimize gastrointestinal side effects 1
• Do not discontinue therapy prematurely due to mild nausea—symptoms typically resolve within 1-2 days while continuing treatment 2