CHAPTER 7: ADRENERGIC ANTAGONISTS- Alpha Adrenergic Blockers

Question 1

Adrenergic antagonist mechanism

Answer 1

they bind to adrenoceptors but do not trigger usual receptor-mediated intracellular effects

Question 2

do they work irreversibly or reversibly

Answer 2

work both ways by attaching to adrenoceptors, prevent activation by endogenous/exogenous agonists

Question 3

sites of action: adrenergic antagonists

Answer 3

BLOCK THE SNS–> PSNS acts uncontrollably as result
- mydriasis
- inc GI secretion
- bronchoconstriction
- relaxed sphincters
-lowered BP

Question 4

what are the 2 types and their subclasses?

Answer 4

alpha receptor
- non selective
- a1
- a2

beta receptor
- non selective first gen
- b1 selective second gen
- non selective third gen
- b1 selective third gen

Question 5

alpha blockers do what?

Answer 5

non selective alpha blockers DEC peripheral resistance, INC cardiac output
- affect BP

• a2 selective have limited clinical utility

Question 6

what are the alpha blocking agents?

Answer 6

phenoxybenzamine- nonselec noncompetitive blocker of a1 and a2
phentolamine- competitive blocker of a1 and a2
prazosin, terazosin, doxazosin- selective competitive blocker of a1
yohimbine- selective competitive a2

Question 7

Phenoxybenzamine- cardiac effects

Answer 7

-block a1 vasoconstriction of peripheral blood vessels caused by endogenous catecholamines
-DEC peripheral resistance
-REFLEX tachycardia

-block presynaptic a2 on symp nerve terminals in heart
- INC NE release

-inc HR and cardiac output b\
-cardiac arrhythmias and anginal pain

Question 8

what is angina?

Answer 8

chest pain as a result of reduced O2 to the heart

Question 9

phenoxybenzamine- epinephrine reversal

Answer 9

vasoconstrictive action of epinephrine is interrupted
BUT vasodilation of other vascular beds caused by stimulation of B receptors is NOT blocked
(b2 vasodilation)

Question 10

epinephrine reversal is done with?

Answer 10

ALL a-adrenergic blockers reverse the a-agonist actions of epinephrine

Question 11

alpha adrenergic blockers have no effect on actions of….

Answer 11

ISOPROTERENOL, its a pure beta agonist

Question 12

phenoxybenzamine- therapeutic uses/indications

Answer 12

treat sweating, hypertension associated with pheochromocytoma
sometimes treats Raynaud disease and frostbite

Question 13

what is pheochromocytoma?

Answer 13

catecholamine secreting tumor of cells derived from the adrenal medulla
- cancer of adrenal medulla

Question 14

phenoxybenzamine should be used with caution in patient with what diseases?

Answer 14

cardiovascular or cerebrovascular diseases (contraindication)

Question 15

Phentolamine- actions

Answer 15

• a1 and a2 competitive blockers
• similar to phenoxybenzamine actions

Question 16

Phentolamine- therapeutic uses/indications

Answer 16

-DIAGNOSIS and short term management of pheochromocytoma
-prevent dermal necrosis following extravasation of NE
-treat hypertensive crisis due to abrupt withdrawal of clonidine or ingestion of tyramine containing food in PTs taking monoamine oxidase inhibitors

Question 17

what is extravasation?

Answer 17

leakage of IV administered solution into surrounding tissues

Question 18

prazosin, terazosin, doxasozin (PTsD pneumonic)- what are they

Answer 18

• selective, competitive alpha 1 blockers
• metabolism leads to inactive products that are excreted in urine except for those of doxazosin (appear in feces)

Question 19

pra,ter,doxazosin- actions

Answer 19

-DEC peripheral vasc resistance/LOWER BP
- relax arterial and venous smooth muscle

• MINIMAL cardiac output/renal blood flow/glomerular filtration rate changes

Question 20

pra,ter,doxazosin -therapuetic uses/indications

Answer 20

-treate hypertension
-first dose may produce exaggerated orthostatic hypotensive response, result in syncope(fainting)
-NOT used as monotherapy for hypertension treatment

Question 21

first dose effect

Answer 21

a drug induces an exaggerated orthostatic hypotensive result that may result in fainting

low BP=faint

Question 22

pra, ter, doxazosin- adverse effects

Answer 22

a1 blockers may cause
-diziness (CNS)
-headache (CNS)
-lack of energy
-nasal congestion
-drowsiness
-orthostatic hypotension

additive hypertensive effect when a1 blocker given with vasodilators (nitrates, PDE 5 inhibitors like slidenafil)

Question 23

Yohimbine- where is it found, how does it work

Answer 23

• found as part of bark of yohimbine tree, can be used as sexual stimulant
  -treat erectile dysfunction
  -works in CNS to inc SNS outflow to periphery
  -contraindicated in CNS and cardiovasc bc its a CNS/cardiovasc stimulant