What it is
Amlodipine is a third-generation dihydropyridine calcium channel blocker with a long action (24 hours). It inhibits calcium entry into vascular smooth muscle and heart cells, causing vasodilation and lowering blood pressure with minimal negative effect on cardiac contractility.
It is first line in essential hypertension, especially if there is angina. Very well tolerated: no cough, no hyperkalaemia. Less heart protection than ACE inhibitors, but better tolerance.
Mechanism of action
It inhibits:
- L-type calcium channels in vascular smooth muscle cells
- Peripheral arteriolar vasodilation without significant reflex tachycardia (long duration)
- Minimal effect on cardiac contractility (vascular selectivity)
At the counter
When to recommend it
- Essential hypertension (first line)
- Stable angina (it reduces ischaemia)
- Coronary artery disease with hypertension
- Raynaud's phenomenon (a common use, on prescription)
When not to
- Allergy to dihydropyridines
- Cardiogenic shock or severe low blood pressure
- Severe aortic stenosis
- Pregnancy: only if there is no safer alternative (the doctor decides)
Warnings
- Important Peripheral oedema (ankles): common, especially at 10 mg. Bothersome but not serious; it does not usually mean stopping. Tell it apart from heart failure (breathlessness, tiredness).
- Caution Low blood pressure: especially with the first dose. Gradual dose increases are recommended.
- Caution Headache and facial flushing: common at the start but usually go away.
- Caution With simvastatin: do not exceed 20 mg of simvastatin a day (amlodipine inhibits its metabolism).
Pharmacokinetics
- Absorption
- Slow, prolonged oral absorption. Bioavailability of 64–90%. Peak at 6–12 hours.
- Distribution
- Wide tissue distribution. Protein binding of 93%. It crosses the placenta.
- Metabolism
- Extensive hepatic metabolism via CYP3A4. It mainly produces inactive metabolites.
- Elimination
- Mainly renal (as metabolites). Very long half-life (30–50 hours), allowing a single daily dose.
Amlodipine vs enalapril
| Aspect | Amlodipine | Enalapril |
|---|---|---|
| Blood pressure effect | High | High |
| Heart protection | Moderate | High (especially in heart failure) |
| Dry cough | No | Yes (common) |
| Peripheral oedema | Common | No |
| Ideal indication | Hypertension + angina | Hypertension + heart failure |
Amlodipine for hypertension + angina, with excellent tolerance. Enalapril if there is heart failure.
Self-assessment
Three questions. When you check your answers you will see the explanation for each one.
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Amlodipine is a calcium channel blocker: it inhibits the calcium entry needed for muscle contraction.
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Mild ankle oedema is very common with amlodipine and not serious. It should not be confused with heart failure: if there is breathlessness or tiredness, get checked.
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Amlodipine's long half-life allows once-daily dosing. That improves adherence.
Training content. It does not replace the summary of product characteristics or clinical judgement.