**6.1 Nifedipine**

It is a dihydropyridine that does not resemble the other calcium antagonists in chemical structure. Although it is not a nitrate, its nitro group is essential for its antianginal effect. Also, it has peripheral vasodilatory effects. It works by inhibiting the voltage-dependent calcium channel in the vascular smooth muscles and has little or no direct suppressant effect on the SA or AV nodes. Nifedipine is thought to be more effective in patients with coronary vasospasm, and it is usually used for vasospastic angina along with angina pectoris.

Additionally, it is used in selected patients to treat hypertension because of its vasodilatory properties. Nifedipine has efficient absorption with buccal or oral administration. Around 90% of nifedipine is protein-bound. The bioavailability of an oral dose reaches 65%. Nifedipine gets metabolized into two inactive metabolites which are found in equilibrium with each other. Only a limited amount of unchanged nifedipine is found in the urine [7].
