Indication
Amlodipine is a calcium channel blocker and may be used alone or in combination with other antihypertensive and antianginal agents for the treatment of Hypertension and Coronary Artery Disease (such as Chronic Stable Angina, Vasospastic Angina and Angiographically Documented Coronary Artery Disease in patients without heart failure or an ejection fraction < 40%) .
Pharmacology
Amlodipine is a long-acting calcium channel blocker that inhibits the transmembrane influx of calcium ions into vascular smooth muscle and cardiac muscle. Thus it causes reduction in peripheral vascular resistance and contractile process in cardiac muscle and reduces blood pressure.The mechanism of the antihypertensive action is due to a direct relaxant effect on vascular smooth muscle. The precise mechanism by which amlodipine relieves angina has not been fully determined but Amlodipine reduces total ischemic burden by the following two actions:
Amlodipine dilates peripheral arterioles and thus, reduces the total peripheral resistance (after load) against which the heart works. Since the heart rate remains stable, this unloading of the heart reduces myocardial energy consumption and oxygen requirements.
The mechanism of action of Amlodipine also probably involves dilatation of the main coronary arteries and coronary arterioles, both in normal and ischemic regions. This dilation increases myocardial oxygen delivery in patients with coronary artery spasm (prinzmetals or variant angina).
Dosage
Adult: Starting dose 5 mg once daily with maximum dose 10 mg once daily.Pediatric: Starting dose 2.5 mg to 5 mg once daily.Small, Fragile and Elderly patients or patients with hepatic insufficiency: Starting dose 2.5 mg once daily.
Interaction
Amlodipine has been safely administered with thiazide diuretics, alpha blockers, beta blockers, angiotensin-converting enzyme inhibitors, long-acting nitrates, sublingual nitroglycerine, non-steroidal anti-inflammatory drugs, antibiotics, and oral hypoglycemic drugs. Amlodipine has no effect on protein binding of digoxin, phenytoin, warfarin, or indomethacin. Administration of Amlodipine with grapefruit or grapefruit juice is not recommended as bioavailability may be increased in some patients resulting in increased blood pressure lowering effects.
Contradiction
It is contraindicated in patients with known sensitivity to Amlodipine.
Side Effect
Most common side effects are headache and edema which occurred in a dose related manner. Other side effects not dose related but reported with an incidence >1.0% are headache, fatigue, nausea, abdominal pain and somnolence.
Pregnancy
Pregnancy Category C. There are no adequate and well-controlled studies of Amlodipine in pregnant women. Amlodipine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is not known whether Amlodipine is excreted in human milk. In the absence of this information, it is recommended that nursing be discontinued while Amlodipine is administered.
Precaution
Symptomatic hypotension is possible, particularly in patients with severe aortic stenosis. However, because of the gradual onset of action, acute hypotension is unlikely. Worsening angina and acute myocardial infarction can develop after starting or increasing the dose of Amlodipine, particularly in patients with severe obstructive coronary artery disease. Titrate slowly when administering calcium channel blockers to patients with severe hepatic impairment.
Overdose
In humans, experience with intentional overdose is limited.Symptoms: Available data suggest that large overdosage could result in excessive peripheral vasodilatation and possibly reflex tachycardia. Marked and probably prolonged systemic hypotension up to and including shock with fatal outcome have been reported.Management: Clinically significant hypotension due to amlodipine overdosage calls for active cardiovascular support including frequent monitoring of cardiac and respiratory function, elevation of extremities, and attention to circulating fluid volume and urine output. A vasoconstrictor may be helpful in restoring vascular tone and blood pressure, provided that there is no contraindication to its use. Intravenous calcium gluconate may be beneficial in reversing the effects of calcium channel blockade. Gastric lavage may be worthwhile in some cases. In healthy volunteers the use of charcoal up to 2 hours after administration of amlodipine 10 mg has been shown to reduce the absorption rate of amlodipine. Since amlodipine is highly protein-bound, dialysis is not likely to be of benefit.
Storage
keep in a dry place away from light and heat. Keep out of the reach of children.