prazosin

Question 1

What is the pharmacological classification of Prazosin?

Answer 1

Selective and competitive Alpha-1 (α1) adrenoceptor antagonist.

Question 2

How does Prazosin affect heart rate compared to Phentolamine?

Answer 2

Prazosin causes minimal/no tachycardia because it spares the Alpha-2 ‘brake’ on NE release.

Question 3

What is the ‘First-Dose Phenomenon’ of Prazosin?

Answer 3

Sudden postural hypotension and syncope (fainting) occurring shortly after the very first dose.

Question 4

How should a doctor instruct a patient to take their first dose of Prazosin?

Answer 4

Take a low dose (0.5mg) at bedtime to prevent syncopal attacks.

Question 5

What is the effect of Prazosin on preload and afterload?

Answer 5

It decreases both by causing vasodilation of both veins (preload) and arteries (afterload).

Question 6

List three therapeutic uses of Prazosin.

Answer 6

1. Hypertension; 2. Benign Prostatic Hyperplasia (BPH); 3. Raynaud’s Disease.

Question 7

Why is Prazosin used in Raynaud’s disease?

Answer 7

It blocks Alpha-1 mediated vasospasm in peripheral digital vessels.

Question 8

What is the plasma half-life of Prazosin?

Answer 8

Approximately 3 hours (requires frequent dosing).

Question 9

Name two longer-acting analogs of Prazosin.

Answer 9

Terazosin and Doxazosin (once-daily dosing).

Question 10

Does Prazosin cause nasal congestion? Why?

Answer 10

Yes; it causes vasodilation of the nasal mucosa vessels (Alpha-1 blockade).

Question 11

Is Prazosin a first-line drug for Hypertension?

Answer 11

No; it is typically used as an add-on therapy in resistant hypertension.

Question 12

Why is Prazosin effective in BPH?

Answer 12

It relaxes smooth muscle in the bladder neck and prostate capsule, improving urinary flow.