Carbamazepine × Clarithromycin

Carbamazepine is broken down in the liver mainly by CYP3A4, and clarithromycin inhibits this enzyme, so carbamazepine blood levels rise (carbamazepine SmPC). In clinical studies the increase was modest but statistically significant (clarithromycin SmPC). The interaction also works the other way: carbamazepine speeds up the breakdown of clarithromycin, and antibiotic levels may fall below the therapeutic range (clarithromycin SmPC).

Dizziness, drowsiness, unsteady gait, double vision, nausea. On the antibiotic side, a weaker response to treatment of the infection because of low clarithromycin levels.

The combination can be used with monitoring. While the patient takes both drugs, monitor carbamazepine blood levels and adjust the dose if needed (carbamazepine SmPC). The US Food and Drug Administration (FDA) also advises close monitoring of carbamazepine levels and notes that the dose may need adjusting (carbamazepine FDA label). High carbamazepine levels cause dizziness, drowsiness, unsteady gait and double vision (carbamazepine SmPC). Use clarithromycin with caution in patients on carbamazepine because the antibiotic may be less effective (clarithromycin SmPC).