Amlodipine (Norvasc) is a dihydropyridine calcium channel blocker used to treat hypertension and angina. It works by blocking L-type voltage-gated calcium channels in vascular smooth muscle, causing vasodilation and reducing blood pressure with a gradual onset of 6–12 hours. Common side effects include peripheral edema (ankle swelling), flushing, and headache. Its exceptionally long half-life of 30–50 hours allows once-daily dosing; it must be used with caution in patients with severe aortic stenosis.
Amlodipine
Uses & FDA Indications
Amlodipine is among the most commonly prescribed antihypertensive medications worldwide. Its long half-life allows once-daily dosing, and its gradual onset minimizes reflex tachycardia — advantages that have contributed to its widespread clinical adoption.
Hypertension
Amlodipine is FDA-approved for the treatment of hypertension in adults and children aged 6 and older. It can be used alone or in combination with other antihypertensive agents. Outcome data from the ALLHAT trial demonstrated that amlodipine-based therapy was as effective as ACE inhibitor-based therapy in preventing cardiovascular events.
Chronic Stable Angina
By dilating coronary arteries and reducing the workload on the heart, amlodipine prevents the chest pain episodes associated with stable angina. It improves exercise tolerance and reduces the frequency of angina attacks.
Vasospastic (Prinzmetal's) Angina
Amlodipine is also approved for vasospastic angina, a form caused by coronary artery spasm rather than fixed atherosclerotic obstruction. Calcium channel blockade directly prevents the arterial spasm responsible for these episodes.
Coronary Artery Disease
The CAMELOT trial demonstrated that amlodipine reduced the need for coronary revascularization and slowed atherosclerosis progression, supporting its use in established CAD beyond blood pressure control alone.
How It Works
Amlodipine belongs to the dihydropyridine class of calcium channel blockers (CCBs). It selectively blocks L-type voltage-gated calcium channels in vascular smooth muscle, preventing calcium entry into cells. Since calcium is required for smooth muscle contraction, blockade results in vasodilation — particularly of arterioles — reducing peripheral vascular resistance and blood pressure.
Unlike non-dihydropyridine CCBs (verapamil, diltiazem), amlodipine has minimal direct effect on the heart's conduction system or contractility at therapeutic doses. Its primary antihypertensive action is peripheral vasodilation rather than cardiac depression, making it generally safe in patients with heart failure with preserved ejection fraction.
Amlodipine's exceptionally long half-life (30–50 hours) means that missed doses have minimal impact on blood pressure control compared to shorter-acting agents. It also results in very gradual drug accumulation and offset, which reduces the risk of abrupt blood pressure changes.
In the coronary vasculature, amlodipine dilates both epicardial arteries and resistance vessels, increasing coronary blood flow and relieving vasospasm. The reduction in afterload (the resistance the heart pumps against) also decreases myocardial oxygen demand, explaining its efficacy in stable angina.
Side Effects
Common
- Peripheral edema (ankle and foot swelling) — the most frequent side effect, affecting 10–30% of patients
- Flushing, sensation of warmth or redness
- Headache (especially in early weeks of therapy)
- Dizziness or lightheadedness
- Palpitations or reflex tachycardia
- Fatigue
Less Common
- Gingival (gum) hyperplasia with long-term use
- Nausea, abdominal discomfort
- Muscle cramps
- Pruritus (itching) or rash
- Gynecomastia (rare, with chronic use)
Managing Peripheral Edema
The ankle edema caused by amlodipine is due to arteriolar dilation without corresponding venous dilation, causing fluid to shift into the interstitial space. This is not related to heart or kidney dysfunction. Elevating legs, adding an ACE inhibitor or ARB (which cause venodilation and help counteract this effect), or switching agents are common strategies.
Drug Interactions
| Drug / Class | Interaction | Clinical Significance |
|---|---|---|
| Simvastatin | Amlodipine inhibits CYP3A4, the primary enzyme metabolizing simvastatin; increases simvastatin exposure and risk of myopathy/rhabdomyolysis | High — simvastatin dose cap recommended when combined with amlodipine |
| Cyclosporine / tacrolimus | Amlodipine inhibits CYP3A4-mediated metabolism, raising immunosuppressant levels | Moderate-High — monitor drug levels and renal function |
| Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) | Increase amlodipine plasma concentrations, potentially causing excessive hypotension | Moderate — monitor blood pressure; dose reduction may be needed |
| Strong CYP3A4 inducers (e.g., rifampin) | Accelerate amlodipine metabolism, potentially reducing antihypertensive efficacy | Moderate — monitor blood pressure and adjust accordingly |
| Beta-blockers | Additive antihypertensive effect; amlodipine lacks significant negative chronotropy, so combination is generally well tolerated | Low — beneficial combination in many patients; monitor for hypotension |
| Grapefruit juice | Inhibits intestinal CYP3A4, increasing amlodipine bioavailability and risk of hypotension | Low-Moderate — avoid large quantities; effect less pronounced than with some other CCBs |
Warnings & Contraindications
⚠ Amlodipine should be used with caution in patients with severe aortic stenosis. Vasodilation without the ability to increase cardiac output can cause severe hypotension or syncope in this population.
Hypotension
Although amlodipine's gradual onset reduces abrupt blood pressure drops, hypotension can still occur, particularly in volume-depleted patients or those on multiple antihypertensive agents. Dizziness upon standing (orthostatic hypotension) warrants dose reassessment.
Worsening Angina / Acute MI
Rarely, amlodipine can worsen angina or trigger myocardial infarction at the time of initiation, particularly in patients with obstructive coronary disease. This is attributed to reflex sympathetic activation from vasodilation. Close monitoring during therapy initiation is advised in high-risk patients.
Hepatic Impairment
Amlodipine is extensively metabolized in the liver. Patients with severe hepatic impairment may have significantly prolonged drug elimination and require careful monitoring.
Frequently Asked Questions
Why do my ankles swell on amlodipine?
Peripheral edema is the most common complaint with amlodipine and affects a significant minority of patients. It occurs because amlodipine dilates small arteries (arterioles) more than veins, increasing capillary hydrostatic pressure and pushing fluid into the surrounding tissue. This swelling is not a sign of heart failure or kidney disease — it is a direct pharmacological effect. Elevating the legs, adding an ACE inhibitor, or adjusting the dose can help.
Can amlodipine be stopped abruptly?
Unlike beta-blockers, amlodipine does not cause dangerous rebound effects when stopped abruptly. However, blood pressure will gradually return to pre-treatment levels over several days, given its long half-life. Stopping without medical guidance is still inadvisable — alternative treatment should be arranged to maintain blood pressure control.
Is amlodipine safe for older adults?
Amlodipine is generally considered safe and effective in elderly patients and is often preferred over diuretics in this population. However, older adults are more susceptible to hypotension and falls from over-treatment. The risk of dizziness and peripheral edema should be monitored, and careful blood pressure management is especially important in those over 75.
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