PHARM: Drugs that Affect Labor

Question 1

List some ACOG indications for elective induction of labor.

Answer 1

• Pre-eclampsia/Eclampsia (and other HTN disorders)
• Maternal Diabetes
• Premature rupture of membranes
• Chorioamnionitis
• Intrauterine fetal growth restriction
• Fetal Demise
• Postterm Pregnancy (at 41 weeks)

Question 2

List some contraindications to labor induction.

Answer 2

active genital herpes infection
placenta or vasa previa
umbilical cord prolapse
fetal malpresentations
previous classical uterine incision

Question 3

What is an “Oxytocic” drug?

Answer 3

a drug to induce labor

Question 4

What is a “tocolytic” drug?

Answer 4

drug to prevent labor

Question 5

What is pitocin?

Answer 5

synthetic analog of oxytocin that leads to uterine SM contractions→ stimulate labor

Question 6

List the prostaglandins used to induce labor.

Answer 6

Dinoprostone
Misoprostol
Carboprost Tromethamine

Question 7

What is dinoprostone?

Answer 7

PGE2 analog

Question 8

What is misoprostol?

Answer 8

PGE1 analog

Question 9

What is carboprost tromethamine?

Answer 9

15-methyl PGF-2alpha

Question 10

List two tocolytics used to delay labor.

Answer 10

Magnesium Sulfate

Indomethacin

Question 11

Which patients are good candidates for indomethacin?

Answer 11

useful in patients less than 32 weeks gestation

Question 12

List some OTCs/herbal remedies used to induce labor.

Answer 12

Caster Oil
Blue Cohosh
Black Cohosh
Oil of the Evening Primrose

Question 13

How do prostaglandin E analogs work in pregnant women?

Answer 13

blocks progesterone and cause a local inflammatory response (PGE2 stimulates cervical ripening)

Question 14

How does carboprost tromethamine work?

Answer 14

binds to progesterone receptors on the myometrium to stimulate uterine contractions

Question 15

MOA: prevents preterm labor by blocking membrane intracellular calcium channels which decreases myometrial contractility

Answer 15

magnesium sulfate

Question 16

MOA: Nonselective COX inhibitor used to treat pre-term labor: blocks formation of gap junctions in the myometrium that increase intracellular calcium and facilitate myometrial contractility.

Answer 16

Indomethacin

Question 17

MOA: Herb with oxytotic effects used for labor induction

Answer 17

Blue Cohosh

Question 18

MOA: Herb with estrogenic effects used for cervical ripening

Answer 18

Black Cohosh

Question 19

MOA: Potentiates effects of prostaglandins for cervical ripening

Answer 19

Oil of the Evening Primrose

Question 20

What is the most commonly used herbal therapy to stimulate labor?

Answer 20

caster oil

Question 21

TOXICITY: Uterine hyperstimulation; post-partum hemorrhage; antidiuretic effect (water intoxication and hyponatremia)

Answer 21

Pitocin

Question 22

TOXICITY: Abruption, intrapartum and postpartum hemorrhage; alteration of FHR and uterine rupture; GI side effects and fever are uncommon with vaginal administration

Answer 22

PGs

Question 23

TOXICITY: 60% of women have flushing, nausea, blurry vision, headache, lethargy, hypotension and pulmonary edema; Mg toxicity (loss of patellar reflexes)

Answer 23

Magnesium Sulfate

Question 24

TOXICITY: nausea, vomiting, gastroesophageal reflux, and gastritis. In addition, platelet dysfunction

Answer 24

indomethacin

Question 25

TOXICITY: Precipitate labor, abruption, severe gastric cramping, diarrhea and dehydration

Answer 25

caster oil

Question 26

TOXICITY: Can lead to abortion because of vasodilatory effects

Answer 26

Black Cohosh

Question 27

FETAL TOXICITY: May lead to primary premature closure of the DA or oligohydramnios in fetus with long-term use; possible necrotizing enterocolitis, intraventricular hemorrhage, and cardiac, pulmonary, and renal abnormalities

Answer 27

Indomethacin

Question 28

What drug is contraindicated in women with myasthenia gravis and should be used in caution in the setting of renal insufficiency because it is excreted by the kidneys.

Answer 28

Magnesium sulfate

Question 29

How long must you wait to give oxytocin after misoprostol?

Answer 29

4 hours

Question 30

How long must you wait to give oxytocin after Dinoprostone?

Answer 30

.5-1 hours

Question 31

What is the ROA of dinoprostone?

Answer 31

Time released suppository left in place for 12 hours

Question 32

Why does the half life of Pitocin alter adverse effects?

Answer 32

Half life is 10-12 minutes so complications like hyperstimulation are rapidly reversible

Question 33

During pregnancy, the placenta releases what hormone that hyperpolarizes the smooth muscle membrane to make it non-excitable and prevents arachidonic acid release (so no PG synthesis)?

Answer 33

progesterone

Question 34

What happens to the uterus as parturition approaches?

Answer 34

estrogen is increased relative to progesterone and increases the number of receptors for contractile agonists and increases the number of gap junctions that electrically couple myometrial cells

Question 35

What are the major uses of oxytocics?

Answer 35

Induce Labor Control postpartum uterine hemorrhage Induce uterine contraction post C-section/uterine surgery Induction of therapeutic abortion

Question 36

What is the major indication for a tocolytic?

Answer 36

slow or arrest delivery for brief periods for therapeutic measures like glucocorticoid therapy to increase fetal surfactant