anti anginal drug
what is anti anginal drug
classification of Anti-anginal drugs
type of antianginal drug
nitrate Drug classification
nitrates MOA Mode of action
pharmacological action of nitrate
pharmacokinetics of nitrates advarce reaction advarce affect of nitrates use of Nitrates
Angina pectoris (or chest pain) is a symptom experien ced due to myocardial ischemia, wherein the blood supply to the heart decreases. As a result, the
heart muscles do not get sufficient oxygen and nutrient s, and fails to work properly.
The following two types of angina are mainly seen:
1) Classic Angina (Angina of Exercise): This angina pain occurs w hen the
demand of oxygen exceeds the s upply of oxygen, most commonly due to diminished coronary flow.
2) Vasospastic (Prinzmetal’s or Variant) Angina: This angina pain occurs at rest and is characterised by reversible coronary vasospasm , which in turn reduces the supply of oxygen.
Some individuals however show mixed angina, characterised by both exercise -induced and resting attacks of angina.
The anti-anginals are divided into the following groups:
1) Vasodilator Drugs
i) Organic Nitrites and Nitrates : Amyl ni trite, Isosorbide dinitrate,
Isosorbide mononitrate, and Nitroglycerine.
ii) Calcium Channel Blockers : Amlodipine, Nifedipine, Diltiazem, and
iii) Potassium Channel Opener: Nicorandil.
2) -Adrenoceptor Antagonists (-Blockers): Atenolol, Metoprolol, Nadolol, and Propranolol.
3) Metabolic Modifiers: Ranolazine and Trimetazidine.
Organic Nitrites and Nitrates
Organic nitrites and nitrates are simple nitric and
nitrous acid esters of glycerol having dif ferent volatilities (e.g., isosorbide dinitrate and isosorbide mononitrate are so lids at room temperature, nitroglycerine is moderately volatile, and amyl nitrite is highly volatile). These compounds are used in angina pectoris. They rapidly reduce the myocardial oxygen demand, followed by rapid relief of symptoms. They are effective in classic as well as in variant angina pectoris.
Mechanism of Action
Nitrates inhibit coronary vasoconstriction or spasm as a result of which perfusion of the myocardium increases, thus, relieving vasospastic angina. Nitrates also cause venodilation, resulting in decreased preload and myocardial oxygen consumption. Due to this action, nitrates are
effectively used in classic angina.
It is believed that organic nitrates ( e.g., nitroglycerine) act on vascular smooth muscles and relax them by their intracellular conversion to nitrite ions and then to nitric oxide. It results in activation of guanylate cyclase and elevates the levels of cGMP. This leads to dephosphorylation of the myosin light chain, causing
vascular smooth muscle relaxation