Vasodilators Flashcards
Nitroprusside Class
Nitrate
Direct peripheral arterial vasodilator
Non-selective relaxation of arterial & venous smooth muscle
Nitroprusside MOA
As NTP is metabolized, it releases nitric oxide and cyanide. NO activates guanylyl cyclase which synthesizes (cGMP), decreases intracellular calcium, which causes smooth muscle dilation
Nitroprusside Use
Reliable antihypertensive
Afterload reducing agent
Nitroprusside Dosing
Infusion: 0.3–10 mcg/kg/min
Nitroprusside Onset and DOA
Onset: 1 minute
DOA: 3 – 5 minutes
Nitroprusside Metabolism
Metabolized in RBC’s to cyanide which is released, then metabolized in the liver and kidneys to thiocyanate (inactive)
Nitroprusside Excretion
Thiocyanate (inactive) is slowly excreted by the kidneys
Nitroprusside Admin Considerations (8)
Caution in patients with aortic stenosis, hypertrophic cardiomyopathy, increased ICP, hypotension, heart failure
May cause headache, tachycardia and bronchodilation
Patients with renal failure may experience a build-up of thiocyantate, which may lead to thyroid dysfunction, muscle weakness, nausea, hypoxia, and an acute toxic psychosis
Dilation of coronary arterioles may result in an intracoronary steal
Reductions in pulmonary artery pressure and the hypoxic pulmonary vasoconstriction mechanism may decrease lung perfusion
Large doses of NTP may lead to methemoglobinemia and is treated with methylene blue to reduce methemoglobinemia to hemoglobin
NTP must be protected from light because of photodegradation
Patient’s on NTP infusions benefit from arterial line monitoring
Nitroglycerin Class
Nitrate
Peripheral vasodilator with venous dilation predominating over arterial dilation
Nitroglycerin MOA
As NTG is metabolized, it releases nitric oxide and cyanide. NO activates guanylyl cyclase which synthesizes (cGMP), decreases intracellular calcium, which causes smooth muscle dilation
Nitroglycerin Uses
Relieves
- Myocardial ischemia
- Coronary vasospasm
- Hypertension
- Ventricular failure
Used for controlled hypotension
Nitroglycerin Dosing
IV Infusion: 5 – 200 mcg/min
SL: 0.4 mg
Nitroglycerin Onset and DOA
Onset: 2 minutes
DOA: 5 minutes
Nitroglycerin Metabolism
Nitroglycerin undergoes rapid reductive hydrolysis in the liver and blood by glutathione-organic nitrate reductase. One metabolic product is nitrite, which can convert hemoglobin to methemoglobin
Also have non-hepatic metabolism via RBCs and Vascular endothelial walls
Nitroglycerin Excretion
Kidneys