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35 Cards in this Set
- Front
- Back
What are the general mechanisms of Direct Acting Vasodilators?
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1. Direct Arteriolar Dilation
2. Decrease TPR 3. Have Reflex Sympathetic Activation (Tachycardia, Increased CO, Fluid retention, and increased renin) 4. Tachyphylaxis (due to reflex mechanisms) |
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True/False: Patients can use Direct Acting Vasodilators alone.
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False.
Usually used in combination with diuretic and BB to balance effects. |
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Name four Direct Acting Vasodilators.
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1. Hydralazine
2. Minoxidil 3. Nitroprusside 4. Diazoxide |
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What is the effect on Veins, Arterioles, Tachycardia, and Sodium Retention of Hydralazine?
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Veins: -
Arterioles: + Tachycardia: + Na Retention: + |
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What is the effect on Veins, Arterioles, Tachycardia, and Sodium Retention of Minoxidil?
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Veins: -
Arterioles: +++ Tachycardia: +++ Na Retention: +++ |
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What is the effect on Veins, Arterioles, Tachycardia, and Sodium Retention of Nitroprusside?
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Veins: +
Arterioles: ++ Tachycardia: + Na Retention: - |
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What is the effect on Veins, Arterioles, Tachycardia, and Sodium Retention of Diazoxide?
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Veins: -/+
Arterioles: +++ Tachycardia: +++ Na Retention: +++ |
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Which Direct Acting Vasodilator can be used without combination therapy with a diuretic and a BB?
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Nitroprusside
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What are the two clinical uses for Direct Acting Vasodilators?
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1. Chronic hypertension
2. Hypertensive crisis |
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Which two medications are used in combination with a diuretic and a BB for chronic hypertension?
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1. Hydralazine
2. Minoxidil |
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Which three medications are used in hypertensive crisis?
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1. Nitroprusside
2. Diazoxide 3. Fenoldopam |
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How are each of the hypertensive crisis drugs administered?
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IV
Diazoxide - 8-10 hours Fenoldopam - less than 48 hours |
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What is the mechanism of action of Hydralazine?
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The mechanism isn't clear. It does not affect veins. It opens Ca++ activated K+ channels, inhibits IP3 induced Ca++, and stimulates NO to increase cGMP.
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What does cGMP do?
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cGMP stimulates phosphotases and stimulates movement of Ca++ out of cells
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What action in the liver is of concern with Hydralazine?
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Hydralazine is N-acetylated in the liver and their are fast and slow acetylators.
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What reflex action does Hydralazine cause?
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Reflex increase in CO and fluid volume.
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What are the side effects of Hydralazine?
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Headache, dizziness, flushing, hypotension, palpitations, nausea, black stool, and "Lupus syndrome" - High dose, long term, women, slow acetylators, Caucasians
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which three conditions are contraindicated for use of Hydralazine?
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1. Coronary artery disease
2. Elderly 3. Ischemia - vasodilation and increased work load ischemia may be severe enough to induce MI |
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How does Minoxidil work?
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Acitvated ATP-modulated K+ channels which increases the K+ efflux causing hyperpolarization and muscle relaxation.
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How is Minoxidil activated?
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By liver sulfotransferase. Minoxidil-SO4 activates channels
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What are six effects of Minoxidil?
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1. Because of more severe hemodynamic actions, the CO is increased 2-3 times which stimulates renin release
2. Myocardial ischemia due to reflexes and sympathetics 3. Arrhythmias due to action on K+ channel, also inverted T waves 4. Salt and water retention increases PCT reabsorption 5. Rashes - Stevens-Johnson syndrome 6. Hypertrichosis - hair growth |
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What is Rogaine?
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Topical application of Minoxidil developed when side effect of hair growth was noticed. Can have CV effects.
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True/False: Using diuretics and BB with Minoxidil is optional.
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False
Always use diuretics and BB for BP effects |
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Describe structure, function, and uses of Nitroprusside.
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Nitroprusside has one NO and 5 cyanide bound to Fe. The NO activates cGMP and decreases intracellular Ca++. This drug affects veins and arterioles. Given by IV infusion and used in hypertensive emergencies, to control hypotension during surgery, and to improve cardiac output in CHF
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What are the side effects of Nitroprusside?
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1. Cyanide toxicity - trembling, vomiting, convulsions
2. Thiocyanate toxicity - weakness, anoxia, tinnitus, muscle spasms, toxic psychosis (long term infusions or renal failure) |
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Is there any way to limit cyanide toxicity with Nitroprusside?
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Give sodium thiosulfate
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What is the mechanism of Diazoxide?
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The mechanism is not fully understood. It's related to thiazides. 3rd line agent. Prolongs open time of ATP-sensitive K+ channels which hyperpolarizes smooth muscle.
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How is Diazoxide administered?
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Given by IV. Long acting.
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When is diazoxide used?
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Hypertensive emergencies but not often used because of marked fall in BP and the unpredictability of its long action.
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What are the adverse events associated with Diazoxide?
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Reflex increase in CO, HR, Renin release, Na+ retention, edema, coronary blood flow.
Cardiac or cerebral ischemia due to decreased pressure |
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What effect does Diazoxide have on insulin?
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Inhibits insulin which increases glucose in Type II diabetics (action on K+ channels to prolong opening)
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True/False: Diazoxide is also used orally to treat hypoglycemic conditions.
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True
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What is the mechanism of Fenoldopam?
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Fenoldopam is a dopamine (D1) agonist that stimulates cAMP. It also have Alpha2 antagonist activity. It is a direct renal natriuretic and diuretic.
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How do you administer Fenoldopam?
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IV infusion. Short term. Less than 48 hours.
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What are the adverse events associated with Fenoldopam?
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Headache, flushing, excessive vasodilation, and dysrhythmias
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