L17 Adrenoceptor antagonist - alpha blockers

Question 1

Phenoxybenzamine is which alpha receptors blocker?

Answer 1

• a1 & a2

Question 2

Effects of phenoxybenzamine on alpha receptors

Answer 2

• a1: orthostatic hypotension
• a2: tarcycardia

Question 3

Therapeutic uses of phenoxybenzamine

Answer 3

• Pheochromocytoma

Question 4

Side effects of phenoxybenzamine

Answer 4

nasal stuffiness
orthostatic hypotension
tarchycardia
inhibition of ejaculation
fatigue
nausea

Question 5

Phentolamine is which alpha receptors blocker?

Answer 5

a1 , a2

Question 6

Therapeutic use of phentolamine

Answer 6

Pheochromocytoma

Question 7

Side effects of phentolamine

Answer 7

Orthostatic hypotension
Tachycardia
Arrhythmias
Myocardial ischemia

Question 8

Prazosin is which alpha antagonist

Answer 8

a1

Question 9

Therapeutic use of prazosin

Answer 9

Antihypertensive
treat BPH (urinary retention)

Question 10

Side effect of prazosin

Answer 10

1st dose phenomenon - sudden and severe drop in BP when change from lying to standing position
- Hypotension
- Nasal congestion
- Headache
- Drowsiness
- Tiredness
- Palpitation

Question 11

Yohimbine is which alpha antagonist

Answer 11

• a2

Question 12

Uses of yohimbine (4)

Answer 12

• treat orthostatic hypotension
• increase BP
• veterinary medicine to reverse anaesthesia produce by xylazine
• treat erectile dysfunction

Question 13

Which alpha antagonists cause pheochromocytoma

Answer 13

• Phenoxybenzamine
• Phentolamine

Question 14

Treat hypertensive emergencies

Answer 14

• labetalol (a1 antagonist) is useful in high BP due to excess circulating conc. of alpha agonists

Question 15

Chronic hypertension

Answer 15

• prazosin

Question 16

Urinary obstruction

Answer 16

• prazosin, doxazosin, terazosin, tamsulosin

Question 17

peripheral vascular disease - occasional raynaud’s phenomenon

Answer 17

prazosin/ phenoxybenzamine
(ca2+ channel blocker more preferable due to side effect of prazosin and phenoxybenzamine)