Oxytocics and Tocolytics

Question 1

Receptors targeted in premature contractions

Answer 1

Beta 2

Question 2

Receptors targeted to induce labor

Answer 2

Alpha 1

Question 3

Agents that stimulate uterine contraction

Answer 3

Oxytocics

Question 4

Agents that relax the uterus

Answer 4

Tocolytics

Question 5

When is labor induction considered

Answer 5

Typically it is only considered when the risks of continuing pregnancy without intervention are greater than the risks of induction

Question 6

In small doses, oxytocin _________. At higher doses, it _________.

Answer 6

In small doses, oxytocin increases both the frequency and the force of uterine contractions. At higher doses, it produces sustained contraction.

Question 7

Half life of oxytocin

Answer 7

5-15 minutes

Question 8

How does oxytocin help post-partum blood loss

Answer 8

Post-partum blood loss can also be minimized using high dose oxytocin to stimulate a sustained contraction. Uterine contraction clamps off blood vessels and prevents further blood loss.

Question 9

How is oxytocin used to “test” labor

Answer 9

A dose of oxytocin is administered to produce a short series of contractions, thus, placental blood flow to the fetus is transiently reduced, similar to true labor. The oxytocin challenge test measures the fetal heart rate response during this infusion and provides the physician information about placental circulatory reserve. An abnormal response, seen as specific decelerations in the fetal heart rate that is being co-monitored with administration of the drug, indicate fetal hypoxia or intolerability to labor and may indicate need for cesarean delivery.

Question 10

How is oxytocin related to ADH

Answer 10

Both produced in the post. pituitary and has a very similar structure. Oxytocin can bind to ADH receptors, so high doses can lead to acute water intoxication (Hyponatremia) which can lead to convulsions, come, death

Question 11

Role of prostoglandins in delivery

Answer 11

Prostaglandins cause cervical ripening (relaxation)

Question 12

Mechanism of prostoglandin action

Answer 12

They alter the extracellular ground substance of the cervix and increase the activity of collagenase in the cervix. By increasing proteoglycan content and changing the biophysical properties of collagen, relaxation of cervical smooth muscle occurs.

Question 13

Example of prostoglandin analogs

Answer 13

Dinoprostone - synthetic prostaglandin E2 analogs, vaginally inserted gel or tablet

Misoprostol (Cytotec) - synthetic PGE1 analog, vaginally inserted in tablet form

Carboprost (Hemabate) - synthetic 15-methylprostaglandin F2 analog, typically injected intramuscularly in an attempt to reduce post-partum hemorrhage, induces uterine contraction

Question 14

Side effects of prostoglandin analogs

Answer 14

Side effects are typically limited to nausea, vomiting, fever

Question 15

Two most common ergot alkaloids

Answer 15

Ergonovine and Methylergonovine.

Question 16

Mechanism of ergot alkaloids

Answer 16

Ergot alkaloids act on alpha-1 adrenergic receptors, dopaminergic, and serotonin receptors.

Question 17

When are ergot alkaloids used and why

Answer 17

Because it does not have a “specific target” it is difficult to tightly control its downstream effects, so although it does produce uterine contractility, it is only used for this purpose when controlling post-partum hemorrhage

Question 18

Side effects of ergot alkaloids

Answer 18

vasospasm, nausea, vomiting, diarrhea, dizziness, arrhythmias, and hallucinations (similar to fungus responsible for LSD).

Question 19

What is mifepristone

Answer 19

An anti-progesterone agent, casues uterine lining decay and producing uterine contraction

Question 20

What is uterine tachysystole

Answer 20

hyperstimulation, more than five contractions in 10 minutes, which may result in placental abruption or uterine rupture.

Question 21

Contraindications for induction of labor

Answer 21

Question 22

When are tocolytics indicated, and most common classes

Answer 22

short-term prolongation of pregnanc

beta-adrenergic receptor agonists, calcium channel blockers or NSAIDs

Question 23

What is Magnesium Sulfate (MgSO4) mostly used for

Answer 23

primary agent to prevent seizures associated with pre-eclampsia and for control of seizures with eclampsia

reduces the severity and risk of cerebral palsy in surviving infants if administered when birth is anticipated before 32 weeks of gestation

Used to be used as a tocolytic because it has a huge list of side effects

Question 24

What is terbatuline and when is it used

Answer 24

β2 receptor adrenergic agonist

Used for short-term labor suppresors when inpatient because mother has top be monitored – can cause sympathetic side effects like hyotension, hyperglycemia, dizziness, anxiety

Also used to counter effects of oxytocin to “reverse” induced labor

Question 25

What is indomethacin and when is it used

Answer 25

NSAID, used to block prostoglandins

Not used after 32 weeks because can cause premature closure of fetal ductus arteriosus which could be disastrous if the newborn has a cardiac anomaly that relies on its patency for oxygenation.

Question 26

Examples of calcium channel blockers

Answer 26

Nifedipine, Procardia

Question 27

Mechanism of calcium channel blockers

Answer 27

The Ca2+ channels are complex proteins composed of distinct subunits (α1, α2, β, δ and γ) encoded by multiple genes. Dihydropyridines (calcium channel blockers) such as nifedipine bind to voltage gated L-type channels and prevent intracellular calcium influx, thus decreasing contraction.

Question 28

Side effects of calcium channel blockers

Answer 28

reduce mean arterial pressures through vasodilation throughout the body, so as expected, side effects that can be seen include hypotension, flushed skin, dizziness, and headache.