Drug Interaction Between Tamiflu and Augmentin
There is no clinically significant drug interaction between Tamiflu (oseltamivir) and Augmentin (amoxicillin-clavulanate), and they can be safely co-administered without dose adjustments.
Pharmacokinetic Basis for Safety
The combination is safe because these medications utilize completely separate metabolic and elimination pathways with no overlap 1:
Oseltamivir metabolism: Approximately 80% is absorbed and converted by hepatic esterases (not CYP enzymes) to its active metabolite, oseltamivir carboxylate, then excreted renally via glomerular filtration and tubular secretion through the anionic pathway 1, 2
Amoxicillin-clavulanate metabolism: Primarily renally excreted unchanged without significant hepatic metabolism 3
No enzyme interactions: Oseltamivir is not a substrate, inhibitor, or inducer of CYP3A4 or P-glycoprotein, eliminating potential interaction pathways 1
Guideline Support
The Advisory Committee on Immunization Practices (ACIP) identifies no contraindications to combination use of influenza antiviral drugs with antibiotics 1. The Infectious Diseases Society of America confirms that neither medication requires dose modification when used together 1.
Critical Exception: The Only Documented Interaction
Probenecid is the sole documented drug that interacts with oseltamivir, reducing oseltamivir carboxylate clearance by approximately 50% through competition for renal tubular secretion 1, 4. Augmentin does not share this mechanism.
Dosing Considerations in Renal Impairment
When co-administering these medications in patients with impaired renal function, adjust oseltamivir dosing based on creatinine clearance 5, 6:
- CrCl >60 mL/min: Oseltamivir 75 mg twice daily (standard dose) 6
- CrCl 30-60 mL/min: Oseltamivir 30 mg twice daily 6
- CrCl 10-30 mL/min: Oseltamivir 75 mg once daily 5, 6
Age alone does not require dose adjustment for oseltamivir, but calculate creatinine clearance as renal function declines with age 6.
Practical Administration Tips
- Timing: Initiate oseltamivir within 48 hours of influenza symptom onset for maximum benefit 6, 1
- Reduce GI side effects: Administer oseltamivir with food to significantly reduce nausea and vomiting (occurs in 10-14% of patients) without affecting absorption 6, 1, 2
- Treatment duration: Standard oseltamivir course is 5 days 2, 4
Monitoring Parameters
Monitor for oseltamivir adverse effects including nausea, vomiting, and mild-to-moderate gastrointestinal symptoms 7. Renal function monitoring is necessary for both drugs, particularly in patients with baseline renal impairment 1.