Amlodipine: Uses, Dosage, Side Effects, and More
1. Drug Name
Generic Name: Amlodipine
Brand Name(s):
- Pakistan: Norvasc
- India: Amlovas, Stamlo
- United States: Norvasc
- United Kingdom: Istin
2. Pharmacological Class
Class: Antihypertensive
Subclass: Calcium channel blocker (dihydropyridine)
3. Mechanism of Action
Amlodipine works by inhibiting the influx of calcium ions into vascular smooth muscle and cardiac muscle. This inhibition results in vasodilation and a reduction in blood pressure, which helps to manage hypertension and angina.
4. Indications
Primary Indications:
- Hypertension
- Chronic stable angina
- Vasospastic angina (Prinzmetal's angina)
Off-label Uses:
- Raynaud's phenomenon
- Coronary artery disease (prevention)
5. Dosage and Administration
Standard Dosage:
- Adults: 5-10 mg once daily.
- Children (6-17 years): 2.5-5 mg once daily.
Route of Administration: Oral (tablets).
Special Populations:
- Pediatric: Adjust dosage based on weight and response.
- Geriatric: Start at the lower end of the dosage range due to increased sensitivity.
6. Pharmacokinetics
Absorption: Well absorbed with peak plasma concentrations occurring 6-12 hours after administration.
Distribution: Widely distributed in the body, 93% bound to plasma proteins.
Metabolism: Extensively metabolized in the liver by cytochrome P450 enzymes.
Excretion: Primarily excreted in urine, with 10% excreted unchanged.
Half-life: Approximately 30-50 hours.
7. Contraindications
Amlodipine is contraindicated in patients with known hypersensitivity to amlodipine or any of its components. It is also contraindicated in patients with severe hypotension, shock, or aortic stenosis.
8. Warnings and Precautions
Use with caution in patients with severe hepatic impairment. Monitor for signs of hypotension, especially in patients with severe aortic stenosis. Use with caution in patients with heart failure as it may increase the risk of worsening symptoms.
9. Side Effects
Common Side Effects: Edema, dizziness, palpitations, flushing, fatigue.
Serious Side Effects: Hypotension, worsening angina, myocardial infarction. Seek immediate medical attention if these occur.
10. Drug Interactions
Major Interactions: May interact with other antihypertensives, increasing the risk of hypotension.
Moderate Interactions: Grapefruit juice may increase the concentration of amlodipine, leading to an increased risk of side effects.
Minor Interactions: Minimal interactions with other drugs.
11. Pregnancy and Lactation
Pregnancy Category: Category C - Risk cannot be ruled out. Use only if clearly needed and the potential benefits justify the potential risk to the fetus.
Breastfeeding Considerations: Amlodipine is excreted in breast milk. Use with caution and consult your doctor before use.
12. Patient Counseling Information
Key Points for Patients:
- Take amlodipine exactly as directed. Do not exceed the recommended dose.
- Avoid sudden discontinuation of the drug as it may worsen angina.
- Inform your doctor about any other medications you are taking to avoid potential interactions.
Administration Tips:
- Take with or without food.
- If a dose is missed, take it as soon as you remember unless it is almost time for the next dose. Do not double the dose to catch up.