L32- Hypothalamic and Pituitary Hormones (posterior)

Question 1

Oxytocin:

• acts on (1) type receptors in order to stimulate (2)
• (3) effect at low doses
• (4) effect at high doses

Answer 1

1- G-protein coupled receptors
2- PG release + LT release –> augments uterine contraction

3- inc force, frequency of contractions (uterine, breast-feeding)

4- sustained contractions, weak antidiuretic / pressor activity (vasopressin receptor activation)

Question 2

list the clinical effects of Oxytocin

Answer 2

Labor Induction (IV): when early vaginal delivery is required; Rh issue, maternal DM, pre-eclampsia, ruptured membranes

Augments Normal Labor (IV): when labor is protracted / displays arrest disorder

Control of uterine hemorrhage (IM)

Question 3

Oxytocin AEs

Answer 3

severe toxicity is rare
-excess stimulation of uterine contractions –> fetal distress, placental abruption, uterine rupture

• inadvertent activation of vasopressin receptors –> excess fluid retention / water toxicity => hyponatremia, HF, seizures, death
• Bolus injections leading to hypotension –> administer IV as dilute solution at controlled rate

Question 4

Oxytocin contraindications

Answer 4

• fetal distress
• prematurity
• abnormal fetal presentation
• cephalopelvic disproportion
• uterine rupture predisposition

Question 5

Oxytoxin Antagonist = (1), and is used for (2)

Answer 5

Atosiban- Tx for preterm labor (NOT in the USA)

Question 6

compare the ADH agonists

Answer 6

• Vasopressin
• Desmopressin: long-acting synthetic analog, minimal V1 activity —– 4000:1 antidiuretic to vasopressor activity ratio

Question 7

describe the direct MOA of ADH agonists

Answer 7

-activates 2 G-protein coupled receptors

V1R: vascular smooth muscle –> contraction (vasopressin > desmopressin)

V2R: renal tubule cells –> inc water permeability and water reabsorption (desmopression > vasopressin)

Question 8

ADH agonist clinical applications

Answer 8

drugs of choice for diabetes insipidus (mainly central DI)

Vasopressin: esophageal variceal bleeding, colonic diverticular bleeding

Desmopressin: coagulopathy Tx in Hemophilia A and VWD

Question 9

ADH agonist AEs

Answer 9

• HAs, nausea, abdominal cramps, allergic reactions

- OD –> hyponatremia, seizures

Question 10

ADH antagonist = (1), affects (2) receptors. used for (3)

Answer 10

1- Conivaptan

2- V1R (pressor), V2R (antidiuretic)

3- hyponatremia due to elevated vasopressin