Pharmacology: Amdepin is a calcium antagonist calcium (slow channel blocker) of he dihydropyridine group. It inhibits the transmembrane influx of calcium ions into cardiac and smooth muscles.
The mechanism of the anti-hypertensive action of Amdepin is due to a direct relaxant effect on vascular of smooth muscles. The precise mechanism by which Amdepin relieves angina has not been fully determined, but Amdepin reduces total ischaemic burden by the following two actions: 1. Amdepin dilates peripheral arterioles and thus reduces the total peripheral resistance (afterload) against which the heart works. Since there is no associated reflex tachycardia, this unloading of the heart reduces myocardial energy consumption and oxygen requirements and probably acccounts for the effectiveness of Amdepin in myocardial ischaemia.
2. The mechanism of action of Amdepin probably involves dilation of the main coronary arteries and coronary arterioles, both in normal and ischaemic regions. This dilation increases myocardial oxygen delivery in patients with coronary artery spasm (Prinzmetal's or variant angina).
After oral administration of therapeutic doses, amlodipine is well absorbed with peak blood levels between 6-12 hour post-dose. The terminal plasma elimination half-life is about 35-50 hours and is consistent with once-daily administraton. Steady state plasma level are reached after 7-8 days.
Amlodipine is predominantly cleared by metabolism to inactive metabolites with most metabolites excreted in the urine. Amlodipine is approximately 97.5% plasma protein bound.
In patients with hypertension, once daily dosing provides clinically significant reductions of blood pressure in both the supine and standing positions throughout the 24 hour interval. Due to the slow onset of action, acute hypotension is not a feature of Amdepin administration.
In patients with angina, once daily administration of Amdepin increases total exercise time and decreases both angina attack frequency and glyceryl trinitrate tablet consumption.
Amdepin has not been associated with any adverse metabolic effects or changes in plasma lipids and is suitable for use in patients with asthma, diabetes and gout.