Modes of action

• Calcium channel blockers cause competitive blockade of cell membrane and slow calcium channels leading to decreased influx of calcium ions into cells. This leads to inhibition of contraction and relaxation of cardiac and smooth muscle fibres resulting in coronary and systemic vasodilatation.

• Nitrates may cause efflux of calcium ions from smooth muscle and cardiac cells and also increase cGMP synthesis resulting in coronary and systemic vasodilatation.

• p-blockers inhibit p-adrenoreceptor stimulation, reducing myocardial work and oxygen consumption. This effect is somewhat offset by compensatory peripheral vasoconstriction.

• Potassium channel openers cause vasodilatation by relaxation of vascular smooth muscle. The potassium channel opening action works on the arterial circulation while a nitrate action provides additional vasodilatation.

• Though aspirin, heparin and clopidogrel have no direct antianginal effect, patients with unstable angina benefit from the reduction in platelet aggregation and thrombus formation.

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