Amlodipine
Amlodipine is a long-acting dihydropyridine calcium-channel blocker used in adults and children for hypertension and chronic stable or vasospastic angina. Its long half-life supports once-daily oral dosing with a stable blood-pressure profile.
- Chemical formula
- C20H25ClN2O5
- CAS number
- 88150-42-9
- ATC code
- C08CA01
- Molecular weight
- 408.88 g/mol
- Drug class
- Dihydropyridine calcium-channel blocker
- Also known as
- UK-48340, Amlodipino
What is it?
Amlodipine is a third-generation dihydropyridine calcium-channel blocker approved in 1990. It is supplied as oral tablets, often as the besylate salt, and is dispensed only on prescription. Amlodipine is one of the most prescribed antihypertensive medications in the world and appears on the World Health Organization List of Essential Medicines. It is also part of fixed-dose combinations with other antihypertensives and statins.
Mechanism of action
Amlodipine selectively blocks L-type calcium channels in vascular smooth muscle, reducing transmembrane calcium influx and producing peripheral arterial vasodilation. The drug has comparatively little direct effect on cardiac contractility or atrioventricular conduction at therapeutic doses. The result is a sustained reduction in systemic vascular resistance and blood pressure, with a parallel improvement in coronary perfusion that supports its anti-anginal effect.
Pharmacokinetics
Amlodipine is slowly absorbed orally, with peak plasma concentrations reached after six to twelve hours. Absolute bioavailability is approximately 60% to 80%. Plasma protein binding is approximately 93%. The drug is extensively metabolised in the liver, mainly by CYP3A4, to inactive metabolites. The terminal half-life is approximately 30 to 50 hours, supporting once-daily dosing. Hepatic impairment substantially increases exposure and requires lower starting doses.
Indications
Amlodipine is approved in adults for the treatment of essential hypertension and chronic stable angina, and for vasospastic (Prinzmetal's) angina. In paediatric patients from age 6, it is approved for hypertension. Amlodipine can be used alone or in combination with other antihypertensives, including angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, diuretics or beta-blockers. According to international guidelines, calcium-channel blockers are one of the recommended first-line classes in hypertension.
Safety profile
Common adverse effects include peripheral oedema (typically ankle), flushing, headache, palpitations and fatigue, mostly dose-related. Peripheral oedema is the most common reason for discontinuation and is more frequent in women. Severe hypotension and reflex tachycardia are uncommon at standard doses. According to the prescribing information, hepatic impairment increases exposure and the dose should be lower in elderly and frail patients. Concomitant strong CYP3A4 inhibitors increase exposure.
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Frequently asked questions
Why does amlodipine cause ankle swelling? ▾
Dihydropyridine calcium-channel blockers preferentially dilate arterioles compared with venules, leading to increased capillary pressure and fluid extravasation, mostly in the lower limbs. Ankle oedema is therefore a class effect of amlodipine and is typically dose-related, more common in women, in older adults and in warm weather. According to the prescribing information, persistent or severe oedema should be reported to the prescriber, who may reduce the dose or switch class.
How long does it take amlodipine to work? ▾
Amlodipine is slowly absorbed and reaches peak plasma concentrations after six to twelve hours, with steady state achieved after about seven to eight days of once-daily dosing. Antihypertensive effect therefore develops gradually over days to weeks. According to the prescribing information, dose adjustment should be guided by blood-pressure response after at least one to two weeks at the same dose.
Can amlodipine be combined with other antihypertensives? ▾
Yes. Amlodipine is frequently combined with renin-angiotensin system blockers, diuretics or beta-blockers in patients who do not reach blood-pressure targets on monotherapy. Several fixed-dose combinations exist. According to international guidelines, combination therapy is preferred in moderate to severe hypertension because it improves blood-pressure control and adherence. The choice of combination is made by the prescriber based on comorbidity and response.
Does grapefruit juice affect amlodipine? ▾
Grapefruit juice can modestly increase amlodipine plasma concentrations through inhibition of intestinal CYP3A4, but the effect is smaller than for some other dihydropyridines such as felodipine. According to the prescribing information, a substantial change in grapefruit consumption should be discussed with the prescriber, particularly in patients with marked blood-pressure changes or in combination with other CYP3A4-active medications.
What are the main contraindications for amlodipine? ▾
Amlodipine is contraindicated in known hypersensitivity to dihydropyridine calcium-channel blockers, in severe hypotension, in shock and in unstable angina shortly after a myocardial infarction. Caution is required in severe aortic stenosis, severe hepatic impairment, in elderly and frail patients, and during pregnancy and breastfeeding. According to the prescribing information, the medical history must be reviewed by a clinician before any prescription.
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