Uterus!

Question 1

What are the layers s of the uterus (3)?

Answer 1

(Outer-Inner) Perimetrium (loose connective tissue), Myometrium (thick muscle), Endometrium (mucous and glandular). And lumen is the cavity.

Question 2

Explain the process of smooth muscle contraction

Answer 2

• Rest - Ca extracellylar&raquo_space; Ca intracellular

Calcium channels open in response to agonists and Ca influx determines the strength of the contraction/muscle shape change

Question 3

What are the two types of drugs that act on the uterus and what do they do?

Answer 3

Stimulants (oxytocic) - induce labour and reduce hemorrhage
Relaxants (tocolytics) - stop or delay premature birth

Question 4

What are the classes of oxytocics (3)?

Answer 4

Oxytocin
Prostaglandins
Ergot Alkaloids

Question 5

What is oxytocin’s synthetic name and what does it do?

Answer 5

Carbetocin - agonist to oxytocin receptors (which are more responsive in late pregnancy) in myometrium

Question 6

What are the adverse effects of Oxytocin?

Answer 6

Uterine rupture and similar to vasopressin (water retention and hyponatremia)

Question 7

What are the contraindications of oxytocin?

Answer 7

Normal labour and abnormal presentation/fetal distress

Question 8

What is the action of Progtaglandins?

Answer 8

PG regulates inflammation, blood flow, GI muscle contraction, and labour

Made by most tissues (including placenta)

Contract Uterus - activating PG receptors

Relax uterus - by producing enzymes that break down collagen - used for cervical ripening

Question 9

What are the clinically used prostaglandins?

Answer 9

Misoprostol (medical abortion, PPH, cervical ripening, and induction of labour)
Dinoprostone (cervical ripening, induction, medical abortion)
Carboprost (abortion and PPH)

Question 10

What are the adverse effects of prostaglandins?

Answer 10

GI upset and fever

Question 11

What are the contra-indications of prostaglandins?

Answer 11

Normal birth, fetal distress, or abnormal fetal position

Question 12

What are the action mechanisms of ergot alkaloid classes?

Answer 12

Organic compounds made by ergot fungus with high affinity agonists of alpha-adrenoceptors - vasoconstriction

(ergonovine, methylergonovine)

Not good for induction, just PPH

Question 13

Adverse effects ergot alkaloids?

Answer 13

Increase BP

Question 14

Contraindications ergot alkaloids?

Answer 14

Hypertension, angina, other CV factors

Question 15

What are the classes of tocolytics (4)?

Answer 15

1. Oxytocin receptor antagonists
2. β2-Adrenoceptor agonists
3. Ca2+ channel blockers
4. Prostaglandin synthesis inhibitors

Question 16

What are the mechanisms of action Oxytocin receptor antagonists?

Answer 16

• Block oxytocin receptors
  (Atosiban)

Question 17

What are the adverse effects Oxytocin receptor antagonists?

Answer 17

Blocks vasopressin receptors = hypotension

Question 18

What are the mechanisms of action β2-Adrenoceptor agonists?

Answer 18

• Activate Beta 2 receptors
  (Terbutaline - only drug approved in Canada)

Question 19

What are the adverse effects β2-Adrenoceptor agonists?

Answer 19

SNS response

Question 20

What are the mechanisms of action Ca2+ channel blockers?

Answer 20

• Blocks calcium channels to slow contractions
  (Nifedipine)

Question 21

What are the adverse effects Ca2+ channel blockers?

Answer 21

Vasodilation - dizzy, headache, flushed

Question 22

What are the mechanisms of action Prostaglandin synthesis inhibitors?

Answer 22

• NSAID blocks synthesis of prostaglandins by inhibiting the cyclooxygenase COX enzymes
  (Indomethacin)

Question 23

What are the adverse effects Prostaglandin synthesis inhibitors?

Answer 23

Premature closing of ductus arteriosis

Question 24

What are the contraindications Prostaglandin synthesis inhibitors?

Answer 24

Pregnancy greater than 30 weeks

Question 25

Explain why NSAIDs should not be used in (late) pregnancy

Answer 25

too much blood will be delivered to lungs