Drugs for heart patients

Classes of drugs acting on heart

• Drugs acting on the heart can be classified into-
  1. Drugs that directly affect the myocardial cells which includes
     • autonomic neurotransmitters and related drugs
     • cardiac glycosides and other inotropic agents
     • antidysrhythmic or antiarrhythmic drugs
  2. Drugs that affect the cardiac function indirectly through actions elsewhere in the vascular system calcium antagonists acting both directly on the myocardial cells and indirectly by relaxing the arterioles.

Autonomic transmitters and related drugs

Both sympathetic and parasympathetic systems exert a tonic effect on the heart at rest.

• The main effects of sympathetic activity on the heart are
  1. positive inotropic effect (increased force of contraction)
  2. positive chronotropic effect ( increased heart rate)
  3. increased automaticity
  4. repolarization and restoration of function following generalized cardiac depolarization
  5. reduced cardiac efficiency.
• The parasympathetic effects include
  1. cardiac slowing and reduced automaticity
  2. decreased force of contraction
  3. inhibition of A-V conduction

Effect of drugs acting on the heart

The effect of drugs on the heart may be expressed as-

1. Inotropic effect if it affects the contractility of heart
2. Chronotropic if it affects the rhythmicity of heart
3. Dromotropic if it affects the conductivity of heart
4. Bathmotropic if it affects the excitability of heart
5. Tonotropic if it affects the tonicity of heart