Mechanism of action
Nitrates cause direct, nonspecific smooth muscle relaxation. This effect occurs due to production of nitric oxide which stimulates formation of cGMP in the smooth muscle cells which lead to dephosphorelation of myosin light chain resulting in smooth muscle relaxation. Repeated frequent administration of high dose of organic nitrates leads to decrease in magnitude of most of their pharmacological actions. Nitrates cause more venodilatation than arteriolar dilatation. Hence pre-load and diastolic pressure is reduced which leads to decreased cardiac work.