nifedipine
dihydropyridine calcium channel blocker· Brands: Adalat, ProcardiaPO
Mechanism of action
Nifedipine inhibits the influx of calcium ions through L-type voltage-gated calcium channels in vascular smooth muscle. This prevents calcium-dependent smooth muscle contraction, resulting in vasodilation, reduced peripheral vascular resistance, and lower blood pressure. It also dilates coronary arteries, improving myocardial oxygen supply. Its action is more potent on vascular smooth muscle than on cardiac muscle, hence it has minimal direct negative inotropic effect.
Pharmacokinetics
Nifedipine is well absorbed after oral administration, but undergoes extensive first-pass hepatic metabolism, resulting in a bioavailability of about 50-70%. It is highly bound to plasma proteins (92-98%). It is metabolised by the hepatic cytochrome P450 enzyme system, primarily CYP3A4, to inactive metabolites. The elimination half-life is approximately 2 hours for immediate-release formulations and 7-10 hours for modified-release formulations. Metabolites are excreted mainly in the urine as inactive compounds.
Indications & dosing
Hypertension
Modified-release preparation. Immediate-release: 10-20 mg three times daily.
- adult · PO: 30–60 mg once daily · Modified-release preparation. Immediate-release: 10-20 mg three times daily.
Chronic stable angina
Modified-release preparation. Immediate-release: 10-20 mg three times daily.
- adult · PO: 30–60 mg once daily · Modified-release preparation. Immediate-release: 10-20 mg three times daily.
Vasospastic angina
Immediate-release preparation. Modified-release: 30-60 mg once daily.
- adult · PO: 10–20 mg three times daily · Immediate-release preparation. Modified-release: 30-60 mg once daily.
Raynaud's phenomenonoff-label
Off-label in some regions; licensed in UK for prophylaxis. Immediate-release preparation.
- adult · PO: 10–20 mg three times daily · Off-label in some regions; licensed in UK for prophylaxis. Immediate-release preparation.
Contraindications & precautions
- Cardiogenic shock · Nifedipine may cause severe hypotension and reflex tachycardia, worsening shock.
- Hypersensitivity to nifedipine or any excipient · Rare but serious reactions possible.
- Severe aortic stenosis · Risk of significant hypotension due to fixed left ventricular outflow obstruction.
- Severe hypotension (systolic blood pressure <90 mmHg) · May exacerbate hypotension; use caution and monitor blood pressure.
- Monitor blood pressure, especially at start of treatment or dose increase.
- Use caution in patients with chronic heart failure, as nifedipine may worsen symptoms.
- Reduce dose in patients with hepatic impairment; nifedipine is metabolised in the liver.
- Avoid concurrent grapefruit juice, which can increase plasma nifedipine concentrations via CYP3A4 inhibition.
- Use caution in patients with coronary artery disease, as reflex tachycardia may provoke angina.
Adverse effects
- Peripheral oedema
- Headache
- Flushing
- Palpitations
- Hypotensionserious
- Exacerbation of angina pectorisserious
- Gingival hyperplasia
- Myocardial infarctionserious
Renal & hepatic adjustment
- eGFR 0+: No dose adjustment required in renal impairment.
- Hepatic impairment (mild): Use with caution; consider a lower initial dose.
- Hepatic impairment (moderate): Use with caution; reduce dose and monitor closely.
- Hepatic impairment (severe): Avoid use in severe hepatic impairment. (avoid)
Monitoring, pregnancy & toxicity
- Blood pressure · At regular intervals during treatment
- Heart rate · At regular intervals during treatment
- Signs of peripheral oedema · At each clinical review
- Anginal symptoms (if used for angina) · At each clinical review
- Pregnancy: Nifedipine may be used in pregnancy for hypertension or preterm labour when clinically indicated. It has not been associated with significant teratogenic risk; however, use in early pregnancy should reflect specialist advice and the balance of benefit versus risk.
- Toxicity: Hypotension and tachycardia (or bradycardia in severe cases) · Supportive measures: IV fluids; calcium gluconate 10% IV; atropine for bradycardia; vasopressors for refractory hypotension.
- Toxicity: Flushing, headache, dizziness, peripheral oedema · Usually self-limiting; observe and monitor vital signs.
- Toxicity: Severe overdose may cause shock, metabolic acidosis, and acute kidney injury · Aggressive supportive care: IV fluids, calcium salts, vasopressors, glucagon; consider haemofiltration in refractory cases.
Antidotes & reversal
- Calcium gluconate (IV) · IV calcium salts restore tone; high-dose insulin-euglycaemia for prolonged toxicity (SR preparations).
Clinical notes
Nifedipine is used for the treatment of hypertension and chronic stable angina. Immediate-release formulations are not recommended for long-term hypertension management due to rapid vasodilation and reflex tachycardia. Extended-release or modified-release formulations are preferred. Common adverse effects include flushing, peripheral oedema, headache, dizziness, and reflex tachycardia. Caution is needed in patients with severe aortic stenosis or heart failure. Grapefruit juice inhibits CYP3A4 and can increase nifedipine levels; advise patients to avoid it. Dose adjustments may be required in hepatic impairment. It should be used with caution during pregnancy and breastfeeding.
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BNF; local formulary