No Clinically Significant Drug Interaction Between Augmentin and Itraconazole
Augmentin (amoxicillin-clavulanate) and itraconazole can be safely co-administered without dose adjustment, as there is no documented pharmacokinetic or pharmacodynamic interaction between these agents. 1, 2
Evidence Analysis
FDA Drug Label Review
The FDA labeling for both medications provides comprehensive drug interaction information:
Itraconazole's interaction profile 1 extensively details its potential for drug-drug interactions through CYP3A4 inhibition and effects on drugs metabolized via this pathway. The label specifically warns about interactions with calcium channel blockers, calcineurin inhibitors, anticoagulants, and various other medication classes. Notably, beta-lactam antibiotics including amoxicillin-clavulanate are not mentioned anywhere in the contraindications or drug interaction sections.
Augmentin's interaction profile 2 lists specific interactions with probenecid (increases amoxicillin levels), oral anticoagulants (may prolong INR), allopurinol (increases rash risk), and potential reduction in oral contraceptive efficacy. Azole antifungals are not mentioned as interacting agents.
Mechanistic Considerations
The absence of interaction is pharmacologically sound:
- Amoxicillin-clavulanate is primarily renally eliminated and does not undergo significant hepatic metabolism via CYP450 enzymes
- Itraconazole is a potent CYP3A4 inhibitor but this mechanism is irrelevant for beta-lactam antibiotics that bypass hepatic metabolism
- Neither agent affects the other's absorption, distribution, or elimination pathways
Supporting Research Evidence
One study 3 examining drug interactions with itraconazole in anticoagulated patients specifically used amoxicillin-clavulanate as the reference comparator group, implicitly confirming its safety profile when combined with itraconazole. This methodological choice would not have been made if there were known interactions between these agents.
Clinical Implications
You can prescribe these medications together without:
- Dose adjustments for either agent
- Additional monitoring beyond what each drug requires individually
- Concerns about altered efficacy or toxicity
Important Caveats
While the combination is safe, remember:
- Itraconazole requires monitoring for its own adverse effects (cardiac function, hepatotoxicity, drug interactions with OTHER medications) 1
- Review the patient's complete medication list for other drugs that DO interact with itraconazole (particularly calcium channel blockers, immunosuppressants, anticoagulants, and QT-prolonging agents) 4, 1
- The guideline evidence 4 emphasizes that azole antifungals have extensive interaction potential with many drug classes, but beta-lactams are not among them