|March 26, 2016|
Amlodipine (as besylate, mesylate or maleate) is a long-acting calcium channel blocker ( dihydropyridine class) used as an anti-hypertensive and in the treatment of angina . Like other calcium channel blockers, amlodipine acts by relaxing the smooth muscle in the arterial wall , decreasing total peripheral resistance and hence reducing blood pressure; in angina it increases blood flow to the heart muscle .
Adverse side effects of the use of amlodipine may be:
The acute oral toxicity ( LD50 ) of amlodipine in mice is 37 mg/kg.
Amlodipine is a dihydropyridine calcium antagonist (calcium ion antagonist or slow-channel blocker) that inhibits the transmembrane influx of calcium ions into vascular smooth muscle and cardiac muscle. Experimental data suggest that amlodipine binds to both dihydropyridine and nondihydropyridine binding sites. The contractile processes of cardiac muscle and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels. Amlodipine inhibits calcium ion influx across cell membranes selectively, with a greater effect on vascular smooth muscle cells than on cardiac muscle cells. Negative inotropic effects can be detected in vitro but such effects have not been seen in intact animals at therapeutic doses. Serum calcium concentration is not affected by amlodipine. Within the physiologic pH range, amlodipine is an ionized compound (pKa=8.6), and its kinetic interaction with the calcium channel receptor is characterized by a gradual rate of association and dissociation with the receptor binding site, resulting in a gradual onset of effect.
Amlodipine is a peripheral arterial vasodilator that acts directly on vascular smooth muscle to cause a reduction in peripheral vascular resistance and reduction in blood pressure.
The precise mechanisms by which amlodipine relieves angina have not been fully delineated, but are thought to include the following:
In patients with exertional angina, amlodipine reduces the total peripheral resistance (afterload) against which the heart works and reduces the rate pressure product, and thus lowers myocardial oxygen demand, at any given level of exercise.
Amlodipine has been demonstrated to block constriction and restore blood flow in coronary arteries and arterioles in response to calcium, potassium epinephrine, serotonin, and thromboxane A2 analog in experimental animal models and in human coronary vessels in vitro. This inhibition of coronary spasm is responsible for the effectiveness of amlodipine in vasospastic (Prinzmetal's or variant) angina.
The recommended starting dose for adults is 5 mg once daily, up to a maximum dose of 10 mg once daily. Small, fragile, or elderly patients, or patients with hepatic insufficiency may be started on 2.5 mg once daily.
The recommended starting dose for pediatric patients is 2.5 mg to 5 mg once daily. Doses in excess of 5 mg daily have not been studied in pediatric patients.
Drug metabolism and excretion
Amlodipine is almost entirely metabolised to inactive metabolites. 10% of the parent substance and 60% of the metabolites are excreted in urine.
Amlodipine is a chiral calcium antagonist, currently on the market and in therapeutic use as a racemate mixture of ( R )-(+)- and ( S )-(???)-amlodipine A method for the semi-preparative chromatographic purification of the enantiomers ( S )-(???)-amlodipine and ( R )-(+)-amlodipine has been reported.
In the United Kingdom tablets of amlodipine from different suppliers may contain different salts. The strength of the tablets is expressed in terms of amlodipine base, i.e., without the salt. Tablets containing different salts are therefore considered interchangeable.
The efficacy and tolerability of a fixed-dose combination of amlodipine 5 mg and perindopril 4 mg, an angiotensin converting enzyme (ACE) inhibitor, have recently been confirmed in a prospective, observational multicentre trial of 1250 hypertensive patients.
Amlodipine is marketed as:
GNU Free Documentation License. It uses material from the Wikipedia article "Amlodipine".
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