Endocrine

Question 1

Oxytocin (Pitocin)

Answer 1

Endogenous Hormone released from Posterior Pituitary gland
Synthetic formation for IV administration

Uses;

• increase my-metrical activity
• induce and augment labor when uterine atony (inadequate contractions)
• induction of labor when medically necessary r/t fetal status
• postpartum (especially after c-section) to contract uterus and decease risk of hemorrhage
• adjunct therapy for partial or inevitable abortion and following D & C procedure
• increase milk ejection and “let down”

MOA;

• stimulates oxytocin receptors on the uterus and causes uterine contraction
• during pregnancy increased oxytocin receptors on linen go uterus, when oxytocin binds to receptor on musculature of uterine wall causes interaction between myosin and actin, smooth muscle contraction

Dose;
Postpartum bleeding; 10 mL IM
gtt; 10 -40 units per 1,000ml of NS or D5 (titrate to sustain uterine contraction)
Allan; rule of 3s
3 units assess in 3 minutes (not adequate uterine tone; give 3 more doses of 3 units until adequate tone)

Pharmacokinetics;

• Onset; 1 min (IV) 3 - 5 min (IM)
• E1/2t; 3 - 5 min
• DOA; 1 hr (IV) 2 - 3 hrs (IM)

oxytocin is inactivated in the liver and kidney; plasma oxytocinase also break down hormone

Side Effects;
mom;
-anaphylaxis, N/V, arrhythmias, PVC, water intoxication, spasm and titanic rupture of uterus, hypertonicity, pelvic hematoma, postpartum hemorrhage

Fetus;
-bradycardia, PVC, arrhythmias, permanent CNS and brain damage, neonatal seizure, lower Apgar score , jaundice, retinal hemorrhage

Contraindicated;
hypersensitivity 
-large fetal head circumference 
-problematic delivery position (breech)
-fetal distress
-hyperactive uterus 
-emergency delivery

Question 2

Octreotide

Answer 2

Somatostatin analogue

Uses;

• tx of adverse hemodynamic effects of carcinoid tumor
• blunts vasoactive and bronchospasm effects of carcinoid tumor
• tx bleeding of esophageal varicies
• tx symptoms of other uncommon endocrine tumors
• stabilize hypoglycemia pt post-op

MOA:
-synthetic somatostatin (GI regulatory peptide “off switch”)
-binds to somatostatin receptors on carcinoid tumors and block release of serotonin and other vasoactive substances; decreases amount of serotonin 5-HIAA in urine)
[[>30mg in urine indicated carcinoid tumor]]
-mimics inhibitory action of somatostatin; decreases GH, TSH, serotonin, gastrin, VIP, insulin, glucagon and reduced gastric acid and pancreatic secretions

MOA for esophageal varicies is thought to be vasoconstriction in splanchnic circulation

Dose;
-Carcinoid tumor 50 - 100 mcg/hr
PRN 25 - 100 mcg
-Variceal bleeding 25 - 50 mcg/hr

Pharmacokinetics

• Peak; 2 hrs
• E1/2 life; 2 hrs
• Clinical effects 8 hrs
• Pb; 65%
• Vd; 14L

metabolized by the liver
32% excreted unchanged in urine

Side Effects;

• IV bolus has caused bradycardia and heart block
• N/V
• decreased GI motility
• constipation
• ab pain
• post prandial hyperglycemia (block insulin release)
• hypoglycemia (decrease glucose release)

Question 3

Argine Vasopressin (AVP)

Answer 3

exogenous antidiuretic peptide (AHD) and vasopressor

Uses;

• tx Diabestes Insipidus (DI)
• uncontrolled hemorrhage of esophageal varies
• alternative to epi for cardiopulmonary resuscitation
• adjunct for hemorrhagic and septic shock

MOA;
works on V1, V2, and V3
V1; vasopressor activity
vascular smooth muscle; potent vasoconstrictor
-works on efferent artery of kidney and no effect on afferent (unlike catecholamine and angiotensin II) maintains GFR
-promotes hemostasis via increasing vWF and VIII
-increases peristalisis by directly stimulating GI smooth muscle

V2; collecting duct in nephron to increases Na and H20 retention

V3; stimulation of ACTH

Dose;
-Refractory Cardiac Arrest; 40 units IV push
-Esophageal Varicies; 20 units IV over 5 min
-Hemorrhagic and septic schock; 0.01 - 0.1 unit/mL
[[>0.05 unit/min CV side effects]]

routes; nasal/ SQ/ IM/ IV

Pharmacokinetics;
-E1/2 t; 10 - 20 min (IV)
(from enzymatic breakdown in tissues especially the kidney)

• metabolism by tissue peptidases
• 33% removed by the kidney

Side Effects;

• IV route can cause;
• coronary artery vasospasm (angina, ischemia, EKG changes)
• increased BP (systemic vasoconstriction)
• N/V ab pain (increased peristalsis)

*NSAID and carbamazepine (tegretol) increase effects of AVP

• secreted from supraoptic & paraventricular nuclei of the anterior hypothalamus.
• stored in posterior pituitary gland
• baroreceptor or osmotic receptor stimulation-triggers exocytosis of AVP from the terminal vesicles into the circulation