Adrenergic Antagonists

Question 1

Phenoxybenzamine

Answer 1

noncompetitive inhibitor of a1 and a2
causes VD and reflex tachycardia

S/e= orthostatic hypotension

can be used for pre-op tx of Pheo with Propranolol

or Raynauds or acrocyanosis

Question 2

Phentolamine pharmacology

Answer 2

non-selective alpha antagonist

CV: decrease BP (a1 block) with reflex tachycardia d/t blockade of a2 autoreceptors–>exs NE–>increase HR

GI: increase motility, inc HCL

Question 3

Phentolamine clinical uses

Answer 3

1) Pheo: pre-op management to prevent hypertensive emergencies
2) Clonidine withdrawal
3) Treat necrosis caused by NE administration
s/e: tachy, n/d, orthostatic hypotension

Question 4

Prazosin

Answer 4

a-1 selective antagonist
**does not block a2 autoreceptors= no reflex tachycardia
tx for HTN and BPH

s/e: SYNCOPE

Question 5

Tamsulosin

Answer 5

competitive a1a with little a1b activity
blocks prostate smooth mm. contraction

limited vascular effects
efficacious in BPH tx

Question 6

Propranolol pharmacology

Answer 6

competitive B1 and B2 antagonist (non selective)

lipid soluble, distributes to the CNS–>drowsiness
decreases HR and CO
slow dec in TPR d/t SNS tone and renin release

blocks lipolysis and glycogenolysis

blocks bronchodilation

2/3 destroyed by first-pass

Question 7

clinical uses of propranolol

Answer 7

1) angina (dec cardiac O2 use)
2) HTN (unk mech)
3) Pheo
4) Thyrotoxicosis (TH elevates levels of B receptors)
4) Anxiety (stage-fright)
5) Post MI–> limits infarct size, Heart failure, mortality

Question 8

Propranolol side effects

Answer 8

dizziness, fatigure, diarrhea, constipation, nausea, depression, bizarre dreams

purpura rash fever

interferes with SGOT and BUN tests

increases VLDL and HDL

Question 9

contraindications of propranolol

Answer 9

1) Diabetics: inhibits compensatory response to hypoglycemia, and masks its early warning signs)
2) Asthmatics and COPD pt (d/t blockage of B2 bronchodilation)
3) Overt heart failure

Question 10

Sudden withdrawal syndrome

Answer 10

after quitting B2 cold turkey
rebound HTN, severe angina, possible MI

Needs to be weaned slowly

Question 11

Metoprolol

Answer 11

selective B1 antagonist (cardioselective)

used in tx of HTN

Question 12

Atenolol

Answer 12

selective B1 antagonist
cardioselective
decreased risk for bronchospasm
allows for normal response to hypoglycemia

Question 13

Labetalol

Answer 13

selective a1 blockers (spares a2)
non selective B blocker

used to treat HTN and Pheo*