Flashcards in Prazosin Deck (28)
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?
-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
What receptors does prazosin work on?
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?
What is the plasma 1/2 life of Prazosin?
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?
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