Medication Classification
Nitroglycerin and sodium nitroprusside are both classified as vasodilators, specifically nitrovasodilators that work by releasing nitric oxide to cause arterial and venous smooth muscle dilation. 1
Mechanism of Action
Both agents function through a shared pharmacologic pathway:
- Nitric oxide release: Both drugs cause intracellular release of nitric oxide, which activates guanylate cyclase, resulting in accumulation of cyclic GMP that produces smooth muscle relaxation 1
- Vasodilatory effects: This mechanism leads to both arterial and venous smooth muscle dilation 1
Differential Hemodynamic Properties
While sharing the same drug class, these agents have distinct hemodynamic profiles:
Nitroglycerin
- Predominantly a venodilator with primary preload-reducing effects 2
- Acts primarily through venodilation to lower preload and rapidly reduce pulmonary congestion 2, 3
- Less potent effect on arterial vasodilation compared to nitroprusside 1
Sodium Nitroprusside
- Balanced vasodilator with combined preload and afterload reduction 2
- Functions as both a preload-reducing venodilator and afterload-reducing arteriodilator 2, 3
- Also dilates the pulmonary vasculature 2, 3
- More potent at producing systemic vasodilation and reducing systemic vascular resistance compared to nitroglycerin 1, 4
Clinical Context
Both agents are used as intravenous vasodilators in acute care settings:
- Recommended for acute heart failure patients with systolic blood pressure >110 mmHg 2
- May be used with caution in patients with systolic blood pressure between 90-110 mmHg 2
- Should be avoided when systolic blood pressure <90 mmHg 2
- Both decrease left and right heart filling pressures and improve dyspnea in acute heart failure 2