Exam 11: Oxytocics

Question 1

What hormone ratio is important in promoting parturition?

Answer 1

Increased estrogen to progesterone

Question 2

What hormone prevents contractions throughout pregnancy?

Answer 2

Progesterone

Question 3

Two mechanisms behind progesterone preventing uterine contractions

Answer 3

1. Hyperpolarizing membrane potential of smooth muscle cells

2. Promoting Ca2+ storage in the sarcoplasmic reticulum

Question 4

3 mechanisms behind estrogen promoting contractions

Answer 4

1. Induction of Na+ channels
2. Induction of gap junctions
3. Induction of oxytocin receptors

Question 5

What causes softening/ripening of the cervix for parturition?

Answer 5

Prostaglandins

Question 6

3 uses for Oxytocics

Answer 6

1. Induction or augmentation of labor
2. Control of postpartum uterine hemorrhage (the number 1 cause of maternal mortality)
3. Induction of abortion or expulsion of dead fetus after intrauterine death

Question 7

2 uses of Tocolytics

Answer 7

1. Delay or prevention of preterm labor

2. Slow or arrest delivery so therapeutic actions can be taken

Question 8

Definition of pre-term labor

Answer 8

Before 37 weeks

Contractions every 10 minutes lasting 30 seconds

Question 9

Chemical composition of Oxytocin

Answer 9

Nonapeptide (9 amino acids)

Question 10

Oxytocin mechanism

Answer 10

Gq (increased calcium, phospholipase C)

Question 11

What causes increased sensitivity of the uterus to oxytocin in gestation?

Answer 11

Estrogen

Question 12

Goal of IV oxytocin in labor induction

Answer 12

3-5 contractions of 60-90 seconds per 10 minute period without fetal distress

Question 13

Most common indication for Oxytocin use in labor induction

Answer 13

Prolonged pregnancy (42 weeks)

Question 14

4 reasons for oxytocin labor induction

Answer 14

1. Mother or fetus is at risk and you need to deliver now
2. Premature rupture of membranes
3. Prolonged pregnancy
4. Selective induction (mom’s choice)

Question 15

Oxytocin effects on breast

Answer 15

Contracts myoepithelial cells forcing milk out of the alveoli of the breast

Question 16

CV side effects of Oxytocin

Answer 16

Hypotension
tachycardia
arrhythmia

Question 17

Electrolyte abnormality associated with Oxytocin use

Answer 17

Hyponatremia due to antidiuretic effect and water retention

Can lead to seizures and death

Question 18

Serious fetal complication associated with oxytocin use

Answer 18

Sustained contraction/hyperstimulation can interfere with fetal circulation

Question 19

Oxytocin contraindications (3)

Answer 19

1. Abnormal fetal position
2. Fetal distress
3. Previous uterine surgery

Question 20

What happens to prostaglandin production in pregnancy?

Answer 20

Increases in the 3rd trimester from the placenta and endometrium

Question 21

PG effect on the uterus (mechanism)

Answer 21

Cause contractions by mediating an increase in intracellular calcium

Question 22

PG effects on cervix (mechanism)

Answer 22

Cervical ripening by increasing secretion of collagenase

Question 23

Dinoprostone

Answer 23

PGE2

Question 24

Prepidil, Cervidil

Answer 24

PGE2 preparations used for cervical ripening

Question 25

2 side effects of PGE2 preparations (prepidil, cervidil)

Answer 25

1. GI disturbance | 2. Uterine hyperstimulation

Question 26

PGE2 contraindications

Answer 26

Same as oxytocin 1. Abnormal fetal position 2. Fetal distress 3. Previous uterine surgery

Question 27

15-methyl PGF2alpha (Carbaprost) Tromethamine | 2 uses

Answer 27

2nd line drug to control postpartum bleeding after oxytocin or ergot alkaloids Can also induce abortion in the second trimester

Question 28

Misoprostol

Answer 28

PGE1 analog Used to terminate early pregnancies (up to 49 days from LMP) Promotes uterine contractions and causes detatchment

Question 29

Ergonovine and Methylergonovine

Answer 29

Ergot Alkaloids Binds alpha-1 receptors, causing an increase in Ca2+ and uterine contractions Used for postpartum or post abortion bleeding

Question 30

Ergonovine and Methylergonovine uses

Answer 30

Postpartum or post abortion bleeding | DO NOT use for labor induction or augmentation

Question 31

Ergot alkaloid side effects

Answer 31

Think alpha 1 HTN due to vasoconstriction NVD Gangrene of the fingers/toes

Question 32

Ergot alkaloid contraindications

Answer 32

HTN CV disease Liver or kidney disease

Question 33

Mifepristone

Answer 33

Progesterone antagonist

Question 34

Mifepristone use, mechanism

Answer 34

Termination of pregnancy up to 49 days from LMP Progesterone antagonist Causes detachment of the products of conception

Question 35

Sodium Chloride 20%, urea 40 50% injection mechanism

Answer 35

Damages mucosa of uterus causing release of Prostaglandins leading to uterine contractions

Question 36

Sodium Chloride 20%, urea 40 50% injection use

Answer 36

late term abortions

Question 37

FDA approved tocolytic agent

Answer 37

There isn't one

Question 38

When are tocolytics used/

Answer 38

to delay premature labor up to 24 hours in patients between 24 and 34 weeks gestation

Question 39

Indomethacin

Answer 39

PG-synthetase inhibitor use to prevent labor at weeks 24-32. Dont use it after 32 weeks or you may cause closure of ductus arteriosus and oligohydramnios

Question 40

nifedipine mechansim

Answer 40

inhibits contractions by decreasing intracellular calcium

Question 41

Nifedipine use in pregnancy

Answer 41

used as a tocolytic between 32-34 weeks because you wouldn't want to use indomethacin that late

Question 42

Terbutaline

Answer 42

B2 agonist Inhibits contraction Very dangerous to mother and fetus Difficult to dose correctly

Question 43

Mg sulfate

Answer 43

Tocolytic decreases intracellular calcium Not very effective at delaying birth