Uterine motility Flashcards
What can cause the stretching of uterine muscle fibers?
estrogens, prostaglandins, oxytocin
High levels of this maintain the uterus in a non-excitable state?
Progesterone
Increased levels of estrogen near the time of birth are important for?
Increasing the expression of oxycotin receptors in the myometrium.
Can labor proceed without oxytocin?
Yes, but the process will be lengthened
What triggers the fetal adrenal gland to make DHEA-s?
Increase production of placental CRH during third trimester
what are the 3 things estrogen causes?
- induce expression of slow sodium channels in myometrial cells.
- increase spread of contraction by increase in number of gab junctions
- increase in number of oxytocin receptors in myometrium.
What is the importance of an increase in prostaglandin production?
To soft and dilate the cervix (cervical ripening)
May also stimulate uterine contractions
What are the uses of drugs that stimulate uterine motility?
- induce or augment labor
- control postpartum uterine hemorrhage/ atony
- cause uterine contraction adter cesarean section
- induce abortion
What are the uses of drugs that decrease uterine motility?
- delay or prevent premature labor before 37 weeks.
2. slow or arrest delivery so other measures can be performed
Which drug is a prohormone produced by magnocellular neurons in the supraoptic and paraventricular nuclei of the hyppothalamus?
Oxytocin
Sensory stimuli such as stretching from the cervix, vagina, and breast causes the release of?
Oxytocin
Oxytocin binding to its receptors in the myometrium result in what cascade?
- increase intracellular Calcium
- activate myosin-light chain kinases
- actin-myosin interactions
- contraction myometrial smooth muscle
When should oxytocin be used in labor induction?
- pregnancy present risk to mother/child
- premature rupture of membranes
- erythroblastosis fetalis
- antepartum bleeding
- placental insufficiency
- prolonged pregnancy
What influence does oxytocin have on breast tissue?
It stimulates contraction of myoepithelial cells which forces milk from the alveoli
What are the adverse effects associated with oxytocin?
Decrease BP, increase HR, arrhythmias
Hyponatremia, water retention
sustained uterine contractions
What substance from the fetus increases late in gestation?
Platelet activating factor, leads to production of prostaglandins
What does Dinoprostone PGE2 do?
- Stimulates uterine contractions, softens and dilates the cervix.
What product is used when labor is going to be induced with oxytocin?
dinoprostone cervical gel.
What are some adverse effects associated with PGE2 or dinoprostone?
GI, uterine hyperstimulation
This drug is given IM to control postpartum bleeding that does not respond to oxytocin or ergot alkaloids.
PGF2 Carboprost tromethamine
This drug is given IM to induce abortion in the second trimester.
PGF2 carboprost tromethamine
This drug is used with the antiprogestin Mifepristone RU486 for early termination of pregnancy.
Misoprostol PGE1
The use of these drugs has increased the number of stillborn children.
Ergot alkaloids (ergonovine, Methylergonovine)
How are ergot alkaloids able to stimulate uterine contractions?
Activate alpha1 adrenergic receptors located in the myometrium.
What should ergot alkaloids be used for?
Control of postpartum or postabortion hemorrhage
What are some adverse effects associated with ergot alkaloids?
Hypertension (methylergonovine less). GI (nausea, vomiting, diarrhea)
This drug is an antiprogestin or progesterone antagonist. What does this drug cause?
Mifepristone-RU486 causes detachment of the products of conception.
What tocolytic agent is a beta2-agonist used to decrease uterine motility?
terbutaline
Describe the cascade of events after terbutaline binds to the beta2 receptor.
- cAMP is generated
- Decrease in contraction
Failure may be due to rapid receptor desensitization
What are the adverse effects associated with terbutaline?
Fetal and maternal tachycardia
Maternal pulmonary edema
Maternal hyperglycemia
Drug of choice for patients with contraindications to terbutaline?
Magnesium sulfate
This drug is a prostaglandin synthetase inhibitor.
Indomethicin
What does indomethicin inhibit?
Inhibit production of F2a and E2 prostaglandins (cause cervical ripening and myometrial contraction)
What side effect can indomethicin cause?
premature closure of the ductus arteriosis and pulmonary hypertension.
What is indomethicin used for?
treat painful menstrual cramps associated with primary dysmenorrhea.
