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Saturday, August 16, 2025

Nifedipine


Introduction

Nifedipine is a calcium channel blocker (CCB) of the dihydropyridine class, widely prescribed for cardiovascular conditions. Its primary therapeutic actions involve vasodilation of arterial smooth muscle and reduction of peripheral vascular resistance, leading to antihypertensive and antianginal effects. Since its introduction in the 1970s, nifedipine has become one of the most commonly used dihydropyridines, particularly in the management of hypertension, chronic stable angina, and certain hypertensive emergencies.

Unlike non-dihydropyridine calcium channel blockers (e.g., verapamil, diltiazem), which act significantly on cardiac conduction, nifedipine has a stronger effect on vascular smooth muscle and relatively less direct effect on the sinoatrial or atrioventricular nodes. This makes it well-suited for conditions characterized by increased systemic vascular resistance, while less appropriate for arrhythmia control.

Pharmacological Classification

  • Class: Dihydropyridine calcium channel blocker

  • ATC code: C08CA05

  • Formulations:

    • Immediate-release capsules (5 mg, 10 mg – less commonly used due to risk of rapid blood pressure drop)

    • Extended-release tablets/capsules (30 mg, 60 mg, 90 mg)

    • Oral suspension (compounded in pediatric or special cases)

    • Intravenous formulations (not widely used in modern practice due to safety concerns)

Mechanism of Action

Nifedipine inhibits the influx of calcium ions through L-type calcium channels in vascular smooth muscle and myocardial cells.

  1. Vasodilation: By reducing intracellular calcium, nifedipine relaxes arterial smooth muscle, resulting in peripheral arterial vasodilation and decreased systemic vascular resistance.

  2. Afterload reduction: The reduced resistance lowers cardiac afterload, improving myocardial oxygen balance.

  3. Coronary artery dilation: Increases coronary blood flow, useful in angina management.

  4. Minimal direct cardiac effect: Unlike verapamil or diltiazem, nifedipine has limited effect on atrioventricular nodal conduction.

Pharmacokinetics

  • Absorption: Rapidly absorbed after oral administration. Bioavailability ~45–70%.

  • Onset of action: 20–30 minutes for immediate-release; 2–6 hours for extended-release.

  • Distribution: Highly protein bound (~90–98%).

  • Metabolism: Extensively metabolized by the liver via CYP3A4 to inactive metabolites.

  • Elimination: Mainly via urine as inactive metabolites.

  • Half-life:

    • Immediate-release: 2–5 hours

    • Extended-release: 6–11 hours (allows once-daily dosing)

Clinical Indications

1. Hypertension

  • First-line or add-on therapy for essential hypertension.

  • Extended-release formulations are recommended for chronic control.

2. Angina Pectoris

  • Chronic stable angina: Reduces frequency of attacks and improves exercise tolerance.

  • Prinzmetal’s (variant) angina: Relieves coronary artery spasm.

3. Hypertensive Emergencies (off-label)

  • Previously used sublingually in emergencies but no longer recommended due to risk of precipitous hypotension and ischemia.

4. Raynaud’s Phenomenon

  • Off-label use in reducing vasospasm in peripheral arteries.

5. Preterm Labor (tocolysis, off-label)

  • Sometimes used to inhibit uterine contractions due to its smooth muscle–relaxant effect.

Contraindications

  • Severe hypotension (systolic <90 mmHg)

  • Cardiogenic shock

  • Advanced aortic stenosis (risk of severe hypotension)

  • Unstable angina or acute myocardial infarction (short-acting formulations increase mortality risk)

  • Known hypersensitivity to nifedipine or excipients

Precautions

  • Heart failure: Use with caution, particularly in reduced ejection fraction.

  • Hepatic impairment: Dosage adjustments may be required.

  • Elderly patients: Greater risk of hypotension and dizziness.

  • Pregnancy: Sometimes used for hypertension or preterm labor but requires specialist supervision.

  • Breastfeeding: Excreted in small amounts; generally considered compatible but requires caution.

Adverse Effects

Common

  • Flushing

  • Headache

  • Dizziness, lightheadedness

  • Peripheral edema (ankle swelling due to precapillary vasodilation)

  • Palpitations or reflex tachycardia

  • Fatigue

Less Common but Important

  • Gingival hyperplasia

  • Constipation

  • Nausea

  • Rash

Rare but Serious

  • Severe hypotension

  • Worsening angina or myocardial infarction (with immediate-release forms)

  • Hepatotoxicity (rare)

Drug Interactions

  • CYP3A4 inhibitors (e.g., ketoconazole, erythromycin, ritonavir): Increase nifedipine plasma concentration, raising risk of toxicity.

  • CYP3A4 inducers (e.g., rifampicin, phenytoin, carbamazepine): Reduce plasma concentration, decreasing efficacy.

  • Beta-blockers: Additive hypotensive effect; may increase risk of heart failure when combined.

  • Grapefruit juice: Inhibits CYP3A4, increasing drug levels.

  • Digoxin: May increase digoxin plasma levels; monitoring required.

  • Quinidine: Altered pharmacokinetics possible; requires monitoring.

Dosage

Hypertension (Adults)

  • Extended-release:

    • Initial: 30 mg once daily

    • Maintenance: 30–60 mg once daily

    • Maximum: 90 mg once daily

  • Immediate-release: Not recommended for chronic use; associated with increased cardiovascular risk.

Angina (Adults)

  • Extended-release:

    • 30–60 mg once daily

    • Titrated according to response

    • Maximum: 120 mg/day (divided if required)

Raynaud’s Phenomenon (Off-label)

  • 10–20 mg three times daily (immediate-release)

  • Extended-release: 30 mg once daily, titrated as needed

Preterm Labor (Off-label, specialist use)

  • Oral 10–20 mg initially, followed by 10–20 mg every 6–8 hours, maximum 120 mg/day

Pediatric Use

  • Not routinely indicated, but sometimes compounded for specific cases under specialist supervision.

Geriatric Patients

  • Start at the lower end of dosing range due to increased sensitivity and altered pharmacokinetics.

Clinical Efficacy

Clinical trials and guideline recommendations place nifedipine (especially extended-release) as:

  • A first-line agent in essential hypertension, particularly effective in older patients and those of African or Asian descent.

  • An effective antianginal medication for reducing frequency of angina attacks and improving exercise tolerance.

  • Superior to placebo and comparably effective to other calcium channel blockers in Raynaud’s phenomenon.

Patient Counseling Points

  • Take extended-release tablets whole; do not crush or chew.

  • Take with or without food, but maintain consistency.

  • Avoid grapefruit juice during therapy.

  • Report side effects such as swelling of ankles, severe dizziness, chest pain worsening, or unusual gum growth.

  • If a dose is missed, take as soon as remembered unless near the time of the next dose.

  • Stand up slowly from sitting or lying positions to minimize dizziness.




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