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heart diseases

Drugs Used to Treat Angina and Their Classification

Angina is the severe sensation of pain over the chest, radiating to inner arm, shoulder and sometimes to the jaw. 

It occurs due to a disturbance in the balance between and oxygen supply and demand. Oxygen lack may occur due to lack of blood supply, severe anaemia or some respiratory disease. Exercise Increases the
demand and hence can provoke an anginal attack in susceptible individuals.

Now the goal of treatment is to restore the balance between oxygen supply and demand.
this is done by either

  1. Increasing the blood supply or
  2. Decreasing the oxygen demand
Drugs that increase the blood supply:-

These drugs dilate the coronary arteries and hence increase the blood supply to the heart muscles which in turn, increases the oxygen supply. 
These drugs include;
                              Tri-nitroglycerine or glyceryl trinitrate
                              Isosorbide mononitrate
                              Isosorbide dinitrate
                              Amyl nitrate (less commonly used)

Isosorbide dinitrate is converted into two molecules of isosorbide mononitrate in the body.

These drugs dilate the coronary vessels and increase the blood and oxygen supply. 

Drugs that Decrease Oxygen Demand.

Drugs included in this category are; 
                                                    1. Beta-blockers

Beta Blockers:
                     Beta-blockers block the activating effects of the sympathetic nervous system on the heart. During the attack of angina sympathetic nervous system is activated which can lead to further aggravation of angina. Because the sympathetic nervous system increases heart rate and contractility and hence oxygen demand.
Most commonly prescribed beta blockers in angina are;

Drugs having mixed action.

These drugs have a dual effect that is they increase oxygen supply by dilating coronary vessels and decrease oxygen demand by slowing impulse conduction. Calcium channel blockers are included in this category

Calcium channel blockers;
                                          Calcium channel blockers that are used in angina are;
                                                    Diltiazem and verapamil.
These calcium channel blockers have a pronounced effect on the heart. other calcium channel blockers (nifedipine, isradipine, felodipine etc) have more peripheral effects and negligible cardiac effects.
Verapamil is more cardio-selective that is, it has a greater effect on the heart. It slows AV conduction and decreases heart rate, it is also used in the treatment of supra-ventricular tachycardia. It has also a vasodilating effect. it dilates peripheral blood vessels and therefore, it decreases preload, afterload and oxygen demand.
Diltiazem has a more or less similar effect.

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