Sympathomimetics

Question 1

What is a sympathomimetic?

Answer 1

A drug the mimics/enhances the effects of NE release from sympathetic nerve terminals.

Question 2

What are the categories of adrenoceptors?

Answer 2

Alpha 1/2 or Beta 1/2/3

Question 3

Discuss the signal transduction for adrenoceptors a2 and Beta

Answer 3

A2-inhibits adenylyl cyclase and reduces cAMP level.

B-adrenoceptor stimulates them.

Question 4

What are the 3 actions of an indirect agonist of adrenoceptors?

Answer 4

1. Displace stored NE from sympathetic nerve terminals.
2. Inhibit NE reuptake
3. Block metabolism of catecholamines.

Question 5

Relate the potencies of direct agonists for adrenoceptors.

Answer 5

Alpha: Epi > NE> isoproterenol
Beta: Isoproterenol > Epi > NE

Question 6

What is the parent compound from which sympathomimetic drugs are derived?

Answer 6

Phenylethylamine; Catecholamines have -OH group on 3 and 4 positions of benzene ring.

Question 7

Describe the relative receptor affinities of alpha agonists.

Answer 7

Phenylephrine: A1 > A2
Clonidine: A2 > A1

Question 8

Describe the relative receptor affinities of mixed alpha and beta agonists.

Answer 8

Norepinephrine: A1 = A2, B1&raquo_space; B2
Epinephrine: A1 = A2, B1 = B2

Question 9

Describe the relative receptor affinities of Beta agonists.

Answer 9

Dobutamine: B1 > B2
Isoproterenol: B1 = B2
Albuterol/Salmeterol: B2 > B1