Amlodipine × Clarithromycin

Clarithromycin inhibits CYP3A4, the enzyme that clears amlodipine, so amlodipine blood levels rise and so does the risk of hypotension (amlodipine SmPC). The labels give no exact figure for this pair. The US Food and Drug Administration (FDA) expects clarithromycin, as a strong inhibitor of the enzyme, to raise amlodipine levels more than diltiazem, which increases them by 60% (amlodipine FDA label). Clarithromycin levels may also rise (clarithromycin SmPC). The effect is stronger in older patients (amlodipine SmPC).

Blood pressure drop: postural dizziness, syncope. Ankle oedema (typical of amlodipine), facial flushing, reflex tachycardia are possible.

The combination can be used, but with caution because of the risk of hypotension (clarithromycin SmPC). During the clarithromycin course, monitor blood pressure and how the patient feels, and lower the amlodipine dose if needed (amlodipine SmPC). The US Food and Drug Administration (FDA) advises using signs of hypotension and swelling to decide whether a dose change is needed (amlodipine FDA label). Watch older patients more closely: the effect is stronger in them (amlodipine SmPC), and most reports of acute kidney injury with clarithromycin and these calcium channel blockers involved patients aged 65 or older (clarithromycin FDA label).