What type of medication is nifedipine (calcium channel blocker)?

Nifedipine: A Dihydropyridine Calcium Channel Blocker

Nifedipine is a dihydropyridine calcium channel blocker that inhibits calcium ion influx across cell membranes of vascular smooth muscle and cardiac muscle, resulting in peripheral arterial vasodilation. 1

Pharmacological Classification and Mechanism

Nifedipine belongs to one of three distinct subclasses of calcium channel blockers:

1. Dihydropyridines (including nifedipine and amlodipine)
2. Benzothiazepines (such as diltiazem)
3. Phenylalkylamines (such as verapamil)

Mechanism of Action

• Selectively inhibits calcium ion influx across cell membranes 1
• Acts primarily on vascular smooth muscle 1
• Causes peripheral arterial vasodilation, reducing peripheral vascular resistance 1
• Does not alter serum calcium concentrations 1

Pharmacological Effects

• Produces marked peripheral arterial vasodilation 2
• Has minimal effect on atrioventricular conduction and heart rate compared to non-dihydropyridines 2
• Causes coronary vasodilation similar to other calcium channel blockers 2

Clinical Distinctions from Other Calcium Channel Blockers

Dihydropyridines like nifedipine differ from non-dihydropyridines (verapamil and diltiazem) in several important ways:

• Vascular Selectivity: Nifedipine is more vascular-selective 3
• Cardiac Effects: Non-dihydropyridines are more myocardial-selective and tend to reduce heart rate 3
• AV Conduction: Nifedipine has minimal effects on AV conduction compared to verapamil and diltiazem 2
• Peripheral Vasodilation: Nifedipine produces more marked peripheral arterial vasodilation than diltiazem 2

Clinical Applications

Nifedipine is used in various cardiovascular conditions:

• Hypertension 1, 4
• Chronic stable angina 5
• Vasospastic (Prinzmetal's) angina 6

For vasospastic angina specifically:

• First-line calcium channel blocker 6
• Maximum dose up to 120 mg/day 6
• More effective than nitrates in alleviating coronary spasm symptoms 6

Important Clinical Considerations

Formulations

• Available in immediate-release and extended-release formulations 1
• Extended-release formulations have approximately 24-hour duration of action 6

Contraindications

• Severe left ventricular dysfunction 6
• Pulmonary edema 6
• Heart failure with reduced ejection fraction 6
• Advanced aortic stenosis 6

Precautions

• Immediate-release nifedipine should not be used without concomitant beta-blockade due to increased risk of adverse cardiovascular events 6, 2
• Use with caution in elderly patients and those with hepatic or renal impairment 6

Common Side Effects

• Hypotension
• Dizziness
• Flushing
• Peripheral edema (more common with nifedipine than other calcium channel blockers) 6

Evidence-Based Considerations

The European Society of Cardiology and American College of Cardiology/American Heart Association guidelines note:

• Calcium channel blockers are recommended for symptom relief in patients already receiving nitrates and beta-blockers 2
• They are useful in patients with contraindications to beta-blockade 2
• They are particularly recommended in patients with vasospastic angina 2
• Nifedipine or other dihydropyridines should not be used without concomitant beta-blocker therapy 2

In acute coronary syndromes, caution is warranted as some studies have shown potential harm with short-acting nifedipine, including the Holland Interuniversity Nifedipine/Metoprolol Trial (HINT) which was stopped early due to concerns about increased risk of reinfarction with nifedipine compared to metoprolol 2.