Nitroglycerin

It is also referred to as “Glyceryl trinitrate”.


Mechanism of action:
Intracellularly, Nitroglycerin gives nitrite ions, which then changes into endothelium derived relaxing factor (EDRF) i.e. nitric oxide. This NO then reacts with sulfhydryl (-SH) containing receptors associated with guanylate cyclase resulting in the activation of soluble Guanylate cyclase which promotes cells’ cyclic GMP level, which activates protein kinase G leading to the dephosphorylation of the myosin light chain. This causes ion binding process of Ca2+and at last relaxation of the vascular smooth muscle.

Actions:

It causes a reduced cardiac work resulting in the decreased oxygen demand of the heart muscles.

1. It causes venodilation so that blood is pooled in the veins resulting in the decreased preload and work of the heart.
2. It causes an increased flow of blood to the myocardium by dilating the coronary vessels.

Pharmacokinetics:
Its onset of action is one minute. It undergoes through the first pass metabolism and that is why it is taken sublingually or via transdermal patches.

Therapeutic uses:
Sublingual nitroglycerin is used for immediate relief from angina induced by physical activity or stress.