amlodipine and cyclosporine

Amlodipine inhibits the CYP3A4 isoenzyme, which is the primary enzyme responsible for metabolising cyclosporine. This inhibition increases cyclosporine plasma concentrations and may lead to cyclosporine toxicity. Additionally, cyclosporine inhibits CYP3A4, which may increase amlodipine concentrations, although this effect is generally less clinically significant. Both drugs also have additive pharmacodynamic effects on vascular tone, potentially causing enhanced hypotension.

Elevated cyclosporine levels can cause nephrotoxicity, hepatotoxicity, neurotoxicity, and hypertension. Patients may experience increased serum creatinine, elevated blood pressure, or other signs of organ toxicity. The magnitude of the interaction is variable and may be more pronounced in patients with pre-existing renal impairment or those on higher doses. Conversely, increased amlodipine levels may lead to excessive hypotension, dizziness, or peripheral oedema.

Monitor cyclosporine trough levels closely, especially after initiating, discontinuing, or changing the dose of amlodipine. Adjust the cyclosporine dose as necessary to maintain therapeutic levels. Monitor renal function, blood pressure, and signs of toxicity. Advise patients to report symptoms such as headache, tremor, or significant hypotension. Consider alternative antihypertensive agents if the interaction cannot be managed.

The interaction is supported by clinical case reports and pharmacokinetic studies. It is recognised in standard drug interaction databases and should be considered clinically significant.