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Drug Reference

amlodipine

dihydropyridine calcium channel blocker· Brands: Amlor, Istin, NorvascPO

Mechanism of action
Amlodipine is a dihydropyridine calcium channel blocker that inhibits the influx of calcium ions across vascular smooth muscle and cardiac muscle cells. It primarily acts on vascular smooth muscle, causing vasodilation and reducing peripheral vascular resistance, which lowers blood pressure. It also relaxes coronary arteries, improving myocardial oxygen supply.
Pharmacokinetics
Amlodipine is well absorbed after oral administration with a bioavailability of 64-90%. It undergoes extensive hepatic metabolism to inactive metabolites, with a half-life of 30-50 hours. Peak plasma concentrations occur 6-12 hours after administration. It is highly protein-bound (about 98%). Excretion is mainly renal, with metabolites and unchanged drug. Steady-state concentrations are achieved after 7-8 days of dosing.
Indications & dosing

Chronic stable angina

Also for vasospastic angina; usual range 5-10 mg daily.

  • adult · PO: 5–10 mg once daily · Also for vasospastic angina; usual range 5-10 mg daily.

Hypertension

Usually started at 5 mg daily; consider 2.5 mg in elderly or hepatic impairment.

  • adult · PO: 5–10 mg once daily · Usually started at 5 mg daily; consider 2.5 mg in elderly or hepatic impairment.

Hypertension

For children 6-17 years; adjust based on response.

  • pediatric · PO: 2.5–5 mg once daily · For children 6-17 years; adjust based on response.
Contraindications & precautions
  • Hypersensitivity to amlodipine or other dihydropyridines · Manifestations include rash, pruritus, angioedema.
  • Cardiogenic shock · Amlodipine may worsen hypotension and haemodynamic instability.
  • Severe aortic stenosis · Vasodilation may cause critical reduction in coronary perfusion; use with caution.
  • Severe hypotension · Avoid in patients with baseline systolic BP < 90 mmHg; monitor blood pressure.
  • Use with caution in patients with heart failure or reduced left ventricular function; amlodipine may cause deterioration in some patients.
  • In hepatic impairment, amlodipine metabolism is reduced; consider a lower initial dose and monitor for adverse effects.
  • Monitor for signs of peripheral oedema; if oedema occurs, assess for other causes (e.g., heart failure) before dose adjustment.
  • CYP3A4 inhibitors (e.g., clarithromycin, itraconazole) can increase amlodipine levels; consider dose reduction to avoid excessive hypotension.
  • Use caution in pregnancy and breastfeeding; amlodipine is not recommended unless the potential benefit outweighs the risk.
Adverse effects
  • Peripheral oedema
  • Flushing
  • Headache
  • Dizziness
  • Palpitations
  • Severe hypotensionserious
  • Angioedemaserious
  • Hepatotoxicityserious
Interactions
  • cyclosporinemajorMonitor 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.
  • doxazosinmoderateMonitor blood pressure, heart rate, and symptoms such as dizziness when initiating or increasing the dose of either drug. Advise patients to rise slowly. Consider dose adjustment if hypotension occurs.
  • simvastatinmajorIf the combination is necessary, limit the simvastatin dose to 20 mg daily, or use an alternative statin that is less dependent on CYP3A4, such as pravastatin or rosuvastatin. Monitor patients for signs of myopathy, and consider measuring creatine kinase if symptoms develop. Do not exceed the recommended dose.
Renal & hepatic adjustment
  • Hepatic impairment (mild): No specific dose adjustment required; monitor for adverse effects.
  • Hepatic impairment (moderate): Consider starting with a lower dose (2.5 mg once daily) and titrate slowly.
  • Hepatic impairment (severe): Avoid use; if necessary, start with 2.5 mg once daily and titrate with extreme caution. (avoid)
Monitoring, pregnancy & toxicity
  • Blood pressure · At initiation and after each dose adjustment
  • Heart rate · Baseline and during titration
  • Peripheral oedema · Regularly during treatment
  • Signs of hypotension (e.g., dizziness, syncope) · After starting therapy and after dose changes
  • Liver function tests · In patients with hepatic impairment
  • Pregnancy: Amlodipine is not recommended in pregnancy, particularly during the first trimester, as there is limited data on its safety. It should only be used if the potential benefit outweighs the risk and alternative antihypertensives (e.g., labetalol, methyldopa) are unsuitable or contraindicated. If used, monitor maternal blood pressure and fetal well-being.
  • Toxicity: Severe hypotension and peripheral vasodilation · Supportive care; IV fluids, IV calcium gluconate or calcium chloride; vasopressors may be required. Monitor closely.
  • Toxicity: Bradycardia and conduction disturbances · Atropine IV for symptomatic bradycardia; temporary pacemaker if refractory; consider IV glucagon; calcium salts may also help.
  • Toxicity: Non-cardiogenic pulmonary oedema · Supportive oxygen therapy and ventilatory support; treat underlying causes; monitor for fluid overload.
Antidotes & reversal
  • Calcium gluconate (IV) · 10-20 mL 10% IV; add high-dose insulin-euglycaemia therapy for refractory vasodilatory shock.
Clinical notes
Amlodipine is used for hypertension and chronic stable angina, and for vasospastic (Prinzmetal's) angina. It can be used alone or in combination with other antihypertensives. Common side effects include peripheral oedema, headache, flushing, and dizziness. It is safe in patients with heart failure, but may cause dose-dependent oedema. Dose adjustment is not required in renal impairment, but caution in hepatic impairment. It has a long half-life, allowing once-daily dosing. It does not cause significant reflex tachycardia. It is not dialysable.

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BNF; local formulary