Pharmacology of Posterior Pituitary Hormones

Question 1

Oxytocin preparations

Answer 1

Pitocin, Syntocinon

Question 2

Vasopressin Agonists

Answer 2

1. Vasopressin (Pitressin)

2. Desmopressin Acetate (DDAVP, Minirin, Stimate)

Question 3

Vasopressin Antagonists

Answer 3

1. Conivaptan HCl (Vaprisol)
2. Tolvaptan (Samsca)
3. Demeclocycline (Declomycin, Declostatin, Ledermycin)

Question 4

Where is ADH/Vasopressin synthesized?

Answer 4

synthesized in the supraoptic and paraventricular nuclei of the hypothalamus and transported down axons to the posterior pituitary

Question 5

Control of ADH secretion

Answer 5

stimulus for secretion is an increase in plasma osmolality above the normal set point

Question 6

Summary of stimuli for ADH secretion

Answer 6

pain, nausea, hypoxia, chronic disease states in which effective circulating volume is reduced

Question 7

ADH release can be reduced by

Answer 7

decrease in plasma osmolality; increase in blood volume; alcohol; nicotine; emotional stress

Question 8

Hormones/NT that stimulate ADH secretion

Answer 8

ACTH; histamine; dopamine; glutamine; aspartate; cholecystokinin; substance P; VIP; prostaglandins; Angiotensin II

Question 9

Hormones/NT that inhibit ADH secretion

Answer 9

atrial natriuretic factor; GABA; opioids

Question 10

Water balance abnormalities can be caused by

Answer 10

Genetic diseases; acquired diseases; pharmaceutical agents

Question 11

Nephrogenic diabetes insipidus is due to

Answer 11

lack of response of kidney collecting tubule cells to ADh stimulations

Question 12

SIADH

Answer 12

excessive ADH production which causes the retention of water resulting in the decrease of effective concentrations of solutes such as sodium

Question 13

Actions of ADH on the kidney

Answer 13

enhance absorption of water from collecting tubule of nephron; acts on the basolateral surface of cells in the cortical and medullary portions of the collecting tubule

Question 14

Other renal sites of ADH actions

Answer 14

glomerular reduction in ultrafiltration; stimulates active reabsorption of NaCl by cells in the medullary thick ascending limbs (osmotic gradient is magnified)

Question 15

V1 receptors mediate

Answer 15

pressor effects - lower affinity for ADH; coupled to phospholipase C

Question 16

V2 receptors mediate

Answer 16

antidiuretic effects - high affinity for ADH; coupled to adenylate cyclase

Question 17

What happens with ADH stimulation of V2 receptors?

Answer 17

aquaporin water channels become inserted into the luminal membrane and the rate of removal of water channels is reduced

Question 18

Prostaglandins (especially PGE) inhibit

Answer 18

antidiuretic action of ADH

Question 19

Lithium inhibits

Answer 19

actions of ADH by inhibiting cAMP production via V2 receptors

Question 20

Demeclocycline inhibits

Answer 20

ADH action through attenuation of cAMP production

Question 21

Demopressin only has what kind of effect?

Answer 21

only antidiuretic effect (little to no pressor effect)

Question 22

Uses of Vaopressin/ADH

Answer 22

1. treatment of neurogenic diabetes insipidus

2. treat esophageal variceal bleeding and colonic diverticular bleeding

Question 23

Toxicity and contraindications of ADH treatment

Answer 23

overdose may result in hyponatremia and seizures; vasopressin (not desmopressin) can cause vasoconstriction so it must be used with caution in patients with CAD

Question 24

Vasopressin receptor antagonists are known as

Answer 24

aquaretics; useful in the treatment of SIADH

Question 25

Tolvaptan has a high affinity for which receptor

Answer 25

high affinity for V2 more than V1

Question 26

Where is oxytocin synthesized?

Answer 26

in the supraoptic and paraventricular nuclei of the hypothalamus

Question 27

Clinical uses of oxytocin

Answer 27

used to induce labor, augment dysfunctional and protracted labor, manage uterine atony or uterine hemorrhage, induce contraction during surgery, in “oxytocin challenge test”

Question 28

Contraindications for oxytocin

Answer 28

fetal distress or abnormal fetal presentation; predisposition for uterine rupture

Question 29

Oxytocin receptor antagonist

Answer 29

Atosiban (Tractocile, Antocin)