Nifedipine: Dihydropyridine Calcium Channel Blocker
Nifedipine is a dihydropyridine (DHP) L-type calcium channel blocker used for hypertension and angina pectoris. It acts primarily on peripheral and coronary vascular smooth muscle, causing vasodilation and reducing blood pressure and cardiac workload.
Short-acting immediate-release formulations are no longer recommended for chronic hypertension due to reflex tachycardia and cardiovascular risk. Modified-release formulations (Adalat LA) are preferred for once- or twice-daily dosing.
Mechanism of Action
Nifedipine blocks L-type voltage-gated calcium channels in vascular smooth muscle and cardiac cells, preventing calcium entry, reducing smooth muscle tone, and causing arteriolar vasodilation. Unlike non-DHP CCBs (diltiazem, verapamil), it has minimal direct cardiac chronotropic or dromotropic effects.
Indications & Use
Chronic stable angina, vasospastic (Prinzmetal) angina, hypertension, Raynaud's phenomenon, hypertensive emergency (immediate-release, limited use). Also off-label for preterm labour (tocolysis).
Dosage
Hypertension/angina: modified-release 30–60 mg once daily (max 90 mg/day). Immediate-release 5–10 mg three times daily only for specific indications (not for chronic BP management). Reduce dose in severe hepatic impairment.
Side Effects
Common: peripheral oedema (ankle swelling, fluid shift), flushing, headache, dizziness. Reflex tachycardia (especially with immediate-release). Gingival hyperplasia with long-term use.
Drug Interactions
CYP3A4 inhibitors (ketoconazole, erythromycin, grapefruit juice): markedly increase nifedipine levels — avoid. CYP3A4 inducers (rifampicin, phenytoin): reduce efficacy. Beta-blockers: can be combined cautiously (risk of excessive BP reduction).
Contraindications
Cardiogenic shock, unstable angina, acute myocardial infarction (within 1 month), significant aortic stenosis. Immediate-release formulations contraindicated for chronic hypertension management.
Frequently Asked Questions
Why should I avoid grapefruit with nifedipine?
Grapefruit contains furanocoumarins that irreversibly inhibit intestinal CYP3A4, significantly increasing nifedipine absorption and blood levels, potentially causing dangerous hypotension and reflex tachycardia.
Why does nifedipine cause leg swelling?
The peripheral oedema is caused by arteriolar dilation without corresponding venodilation, causing fluid to shift from capillaries into surrounding tissue. It is not a sign of heart failure.
What is the difference between immediate-release and modified-release nifedipine?
Immediate-release causes rapid peaks, reflex tachycardia, and is linked to increased cardiovascular events in chronic hypertension. Modified-release provides smooth 24h coverage and is the recommended formulation.
References
- ESC Hypertension Guidelines 2023
- ACTION Trial (nifedipine in stable angina)
- EMA product information nifedipine
Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice.