Nitrates MOA

Q: Anti-anginal effects of nitrates are primarily due to? (select one)

A) coronary vasodilatation

B) systemic vasodilation 

Answer: B

Nitrates are probably one of the oldest but still the first line of drugs for the relief of angina pectoris since last more than 150 years.

Although nitrates indeed vasodilate coronaries the primary anti-anginal effect is systemic vasodilation which reduces the left ventricular systolic wall stress. Nitrates are primarily venodilators, and have a modest arteriolar vasodilator effect. They have a synergetic effect when used with beta-blockers or calcium channel blockers.

Clinicians should stay aware that if a patient is hypovolemic, (s)he may have a precipitate drop in blood pressure due to arteriolar vasodilatation.

Nitrates may have some coronary effect by reversing coronary vasospasm, and indirectly improve subendocardial blood flow in synergism with decreased left ventricular end-diastolic pressure due to its systemic venous dilatation. Nitrates may also lower the resistance to collateral vessel blood flow.

It is less known that nitrates also have antiplatelet and antithrombotic characteristics.

#cardiology

#pharmacology

References:

1. Murrell W. Nitro-glycerine as a remedy for angina pectoris. Lancet 1879; 1:80.

2. Gibbons RJ, Abrams J, Chatterjee K, et al. ACC/AHA 2002 guideline update for the management of patients with chronic stable angina www.acc.org/qualityandscience/clinical/statements.htm (Accessed on August 24, 2006).

3. Abrams J. Hemodynamic effects of nitroglycerin and long-acting nitrates. Am Heart J 1985; 110:216.

4. Knight CJ, Panesar M, Wilson DJ, et al. Different effects of calcium antagonists, nitrates, and beta-blockers on platelet function. Possible importance for the treatment of unstable angina. Circulation 1997; 95:125.

5. Loscalzo J. Antiplatelet and antithrombotic effects of organic nitrates. Am J Cardiol 1992; 70:18B.