Can a Patient Taking Xgeva and Xtandi Take Tamiflu?
Yes, a patient taking Xgeva (denosumab) and Xtandi (enzalutamide) can safely take Tamiflu (oseltamivir), as there are no clinically significant drug interactions between these medications.
Pharmacokinetic Basis for Safety
The combination is safe because these drugs utilize completely independent metabolic and elimination pathways:
Oseltamivir (Tamiflu) is primarily excreted unchanged via the kidneys through glomerular filtration and tubular secretion via the anionic pathway, with minimal hepatic metabolism and no involvement of cytochrome P450 enzymes 1, 2.
Enzalutamide (Xtandi) is primarily metabolized by CYP3A4 and CYP2C8, and acts as a strong inducer of CYP3A4 and moderate inducer of CYP2C9 and CYP2C19 3. Since oseltamivir does not undergo CYP450 metabolism, enzalutamide's induction effects are irrelevant 1.
Denosumab (Xgeva) is a fully human monoclonal antibody that inhibits RANKL and does not undergo hepatic or renal metabolism 4. It has no known drug-drug interactions with either oseltamivir or enzalutamide.
Known Drug Interactions with Oseltamivir
The only documented clinically significant interaction with oseltamivir involves probenecid, which reduces oseltamivir carboxylate clearance by approximately 50% through competition for renal tubular secretion 1, 2. Neither Xgeva nor Xtandi share this mechanism 5.
Clinical Administration Recommendations
Oseltamivir dosing: 75 mg orally twice daily for 5 days, initiated within 48 hours of influenza symptom onset for maximum benefit 5.
Take with food: Administer oseltamivir with food to minimize gastrointestinal side effects (nausea, vomiting), which occur in approximately 10% of patients 1, 2.
Renal adjustment: If creatinine clearance is 10-30 mL/min, reduce oseltamivir dose to 75 mg once daily 5, 2.
Monitoring Considerations
Monitor for oseltamivir's most common adverse effects: nausea (10%), vomiting (9%), and mild gastrointestinal symptoms 2.
Continue Xgeva and Xtandi without dose adjustment, as no interaction exists 1, 5.
Be aware that transient neuropsychiatric events (self-injury or delirium) have been reported postmarketing with oseltamivir, though rare 2.