Amlodipine
Norvasc | Istin | Amlong
Overview
Inhibits calcium ion influx across cell membranes of cardiac and vascular smooth muscle cells, resulting in peripheral arterial vasodilation and reduced blood pressure.
Indications
- Hypertension
- Chronic stable angina
- Vasospastic (Prinzmetal) angina
- Coronary artery disease
Contraindications
- Severe hypotension
- Severe aortic stenosis
- Cardiogenic shock
Classification
Mechanism of Action
Inhibits calcium ion influx across cell membranes of cardiac and vascular smooth muscle cells, resulting in peripheral arterial vasodilation and reduced blood pressure.
Pharmacodynamics
Long-acting dihydropyridine calcium channel blocker. Produces peripheral vasodilation with gradual onset, minimizing reflex tachycardia.
Pharmacokinetics
- Absorption
- Slowly and almost completely absorbed from GI tract. Peak plasma levels in 6-12 hours.
- Distribution
- Volume of distribution ~21 L/kg. Crosses blood-brain barrier.
- Metabolism
- Hepatic (extensive) via CYP3A4 to inactive metabolites.
- Excretion
- Renal (60% as metabolites, 10% unchanged).
- Half-life
- 30-50 hours
- Bioavailability
- 64-90%
- Protein Binding
- 93-98%
Dosage
Typical dosage: 2.5-10mg once daily
Available Forms
- Tablet
Side Effects
Common
- Peripheral edema
- Fatigue
- Dizziness
- Flushing
- Palpitations
Serious
- Hypotension
- Worsening angina
- Myocardial infarction (rare)
Rare
- Hepatitis
- Jaundice
- Gingival hyperplasia
Drug Interactions
Amlodipine may increase simvastatin levels. Limit simvastatin dose to 20mg daily when used with amlodipine.
Amlodipine may increase cyclosporine levels. Monitor cyclosporine levels closely.
Warnings
Pregnancy
Category C
Toxicity
LD50 >40 mg/kg (oral, rat)
Overdose
Symptoms: excessive peripheral vasodilation, marked hypotension, reflex tachycardia. Treatment: IV fluids, vasopressors, calcium gluconate.
References
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