Antiepileptic Drug Interactions with Azithromycin

Mechanism of Interaction

• Azithromycin primarily inhibits P-glycoprotein (P-gp) efflux transporters but does not significantly inhibit cytochrome P450 enzymes, which is a key distinction from other macrolides like erythromycin and clarithromycin 1
• Erythromycin and clarithromycin are potent inhibitors of CYP3A4, the primary enzyme responsible for metabolizing several antiepileptic drugs, according to the MMWR Recommendations and Reports 3

Antiepileptics Affected by Macrolides

• Carbamazepine is extensively metabolized by CYP3A4 and shows clinically significant interactions with erythromycin and clarithromycin, but not with azithromycin, which does not inhibit CYP3A4 1
• Erythromycin can interact with phenytoin through CYP450 inhibition, but azithromycin lacks this CYP450 inhibitory effect, as stated by the Cancer Treatment Reviews 1, 3

Pharmacodynamic Concerns

• Azithromycin can prolong the QT interval and increase the risk of torsades de pointes, which is a pharmacodynamic concern, particularly when combined with other QT-prolonging medications, according to the Cancer Treatment Reviews and MMWR Recommendations and Reports 1, 3
• The American Heart Association recommends monitoring ECG if combining azithromycin with medications that lower seizure threshold or prolong QT interval, as suggested by the Cancer Treatment Reviews 5

Practical Recommendations

• The American College of Clinical Pharmacology recommends azithromycin as the preferred macrolide when antibiotic therapy is needed in patients taking antiepileptic drugs, particularly those on carbamazepine, phenytoin, or other CYP3A4-metabolized antiepileptics 2