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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 jaw. 

It occurs due to disturbance in balance between and oxygen supply and demand. Oxygen lack may occur due to lack of blood supply, severe anemia or some respiratory disease. Exercise Increases the
demand and hence can provoke 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 coronory 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 tri-nitrate
                              Isosorbide mono-nitrate
                              Isosorbide di-nitrate
                              Amyl nitrate (less commonly used)

Iso-sorbide di-nitrate is converted into two molecules of iso-sorbide mono-nitrate 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 catagory are; 
                                                    1. Beta blockers

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

Drugs having mixed action.

These drugs have duel 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 catagory

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

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