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What is the trade name for Prazosin?



What is the formal drug classification for Prazosin?

Selective POST-synaptic alpha 1 adrenergic Antagonist; Antihypertensive


What are the clinical uses for Prazosin?

-essential hypertension
-to decrease afterload in CHF
-preop prep for patients with pheochromocytoma, who exhibit ST changes on ECG
-Reduces Vasospasm in Raynaud syndrome
-essential hypertension in pts with BPH b/c it reduces prostate size
-Ischemic cardiomyopathy


What receptors does prazosin work on?

Alpha 1


Does prazosin block pre- or post- synaptically?

POST-synaptically (alpha 1 antagonist)


What is the MOA of Prazosin?

Selective post-synaptic alpha 1 adrenergic antagonist resulting in vasodilating effects on both arterial and venous vasculature


Does Prazosin work on the arterial or venous vasculature?

Both, BUT has 1,000 fold > affinity for alpha 1 receptors than for alpha-2 receptors


What does the alpha-1 antagonism of Prazosin cause regarding vascular tone? Is there reflex tachycardia? What happens to venous return and CO?

-Decreases SVR without causing reflex tachycardia or increases in renin activity
-Vascular tone in both resistance and capacitance vessels is decreased, resulting in decreased venous return and CO


Since Prazosin is selective for alpha-1 antagonism, what does this mean regarding alpha-2 receptors and NE release?

It leaves the inhibiting effect of Alpha-2 receptor activity on NE release intact, therefore it is less likely to evoke reflex tachycardia!!!!


What does Prazosin do to the vasoconstrictor effects of NE and Epi?

Antagonizes their effects, thereby causing a decline in Peripheral Vascular Resistance, and venous return to the heart


Tell me about the oral absorption of Prazosin

Has substantial 1st pass effect with oral intake, <60% bioavailability after oral administration


Is Prazosin protein bound?

Highly bound to plasma protein


How is Prazosin metabolized?

Via Demethylation and conjugation in the liver


How is Prazosin eliminated?

Bile and Feces


When does Prazosin take peak effect?

3 hours


What is the plasma 1/2 life of Prazosin?

2-3 hours


What is the elimination 1/2 time of Prazosin? but what is a condition that prolongs this?

3-4 hours, prolonged by CHF but NOT renal dysfunction


What are the side effects of Prazosin?

-Syncope with a sudden loss of consciousness with 1st dose, postural and dose related
-Dizziness and Vertigo, Orthostatic Hypotension, Headache, Palpitations, fluid retention, drowsiness, weakness, anticholinergic effects, priapism
-Dryness of the mouth, nasal congestion, nightmares, urinary frequency, lethargy and sexual dysfunction may occur
-MAy cause bronchodilation
-Palpitations, depression, dizziness, weakness


What are serious side effects that may occur from Prazosin?

-Systemic Lupus Erythematous


What are the contraindications with Prazosin?

-Hypersensitivity to Prazosin, Terazosin, or Doxazosin
-Epidural anesthesia hypotension may be exaggerated due to drug induced alpha 1 blockade that prevents compensatory vasoconstriction in the unblocked portions of the body
-Concommitant use of Beta Blockers could result in refractory hypotension during regional anesthesia due to potential blunted responses to beta 1 as well as alpha 1 agonists


What pregnancy category does Prazosin fall under?

C- should only be used in pregnancy if the potential benefit justifies the potential risk to the mother or fetus


What drug interactions with Prazosin cause an additive hypotensive effect?

Antihypertensive Agents
Phosphodiesterase-5 Inhibitor


What drug interaction may occur between Prazosin and NSAIDS?

NSAIDS may interfere with the antihypertensive effect


Which 2 drugs have decreased effectiveness when administered concurrently with Prazosin?



What is the initial PO dose of Prazosin?

1mg PO at bedtime, then titrated slowly to effect


What is the maximum total daily dose of Prazosin?

20mg in divided doses


What has Prazosin been shown to do regarding Lipid profiles?

Improves lipid profiles by lowering LDL levels while raising HDL levels


As a secondary drug in combination with WHICH drug, has Prazosin proved to be effective for hypertension in young patients?

combination with a diuretic