Uterine Drugs Flashcards
What is cervical ripening and why is it important for labor?
It is the softening of the cervix which is necessary for cervical dilation
Describe the mechanism of action for oxytocin.
It is a nonpeptide hormone that is released during labor that binds to receptors altering transmembrane ion currents in the myometrium to cause uterine contraction.
What adverse effects are associated with oxytocin?
Uterine tachysystole (excessively frequent contractions- 6+ in 10 minutes)
Describe the mechanism of action of prostaglandins (misoprostol).
It is a PGE1 that causes uterine stimulation throughout all of gestation and ripens the cervix
What is the clinical indication for misoprostol?
Labor induction and postpartum hemorrhage prevention. Used to induce contractions after a missed/incomplete miscarriage in early pregnancy.
When is misoprostol contraindicated?
In women with previous c-sections
What are common side effects associated with misoprostol?
GI smooth muscle contraction (n/v/d) is common. Bleeding is also possible.
Describe the mechanism of action of ergot alkaloids (methylergometrine).
It is a partial agonist/antagonist at alpha-adrenergic, DA, and 5-HT receptors resulting in vasoconstriction, increased uterine motor activity (force and frequency), and high doses lead to sustained contraction
What adverse effects are associated w/ methylergometrine (ergot alkaloids)?
Elevated BP, n/v are common
With what other medication can you use methylergometrine (ergot alkaloids)?
Oxytocin
What are the clinical indications for ergot alkaloids (methylergometrine)?
It is used to prevent postpartum hemorrhage and prolongs uterine contractions.
When is methylergometrine (ergot alkaloids) contraindicated?
Hypertension (b/c this drug causes vasoconstriction)
Name the tocolytics and the clinical indication for their use.
Magnesium sulfate, terbutaline, nifedipine, atosiban, and indomethicin. They are used to delay preterm delivery to allow time for corticosteroid administration for fetal lung development
What is the general mechanism of action for tocolytics?
They decrease smooth muscle contractions.
What is the mechanism of action of magnesium sulfate?
It is a Ca++ channel blocker that subsequently decreases strength and frequency of uterine contractions
What is the mechanism of action of terbutaline?
It is a beta-2 agonist that inactivates myosin light-chain kinase resulting in relaxation of uterine muscle
Discuss the clinical indications for magnesium sulfate.
It is a tocolytic used for preterm labor before 32 weeks, however it is more commonly used to prevent seizures in preeclampsia and is neuroprotective for the premature fetus.
What adverse effects are associated with magnesium sulfate?
It has a narrow therapeutic index and must monitor blood plasma levels closely for hypermagnesemia, particularly in renal patients. It can also cause pulmonary edema.
What adverse effects are associated with terbutaline?
It can cause reflex tachycardia and in high doses, B1 effects and hypotension. It’s adverse effects to mom and baby limit use.
Name the antenatal corticosteroids and their clinical use.
Dexamethasone and betamethasone. They are used to enhance fetal lung development in preterm labor. Tocolytics are given to allow time for these medications to be administered
Name the uterotonics and the major clinical indication for this class of drugs.
Oxytocin, Prostaglandins (Misoprostol), and Ergot Alkaloids (Methylergometrine). They are used to induce labor once cervical ripening is complete, and also help treat/prevent postpartum hemorrhage.
What is the mechanism of action of Nifedipine?
It is a Ca++ channel blocker.
What is the mechanism of action of indomethicin?
It is an NSAID aka it inhibits prostaglandins
What is the mechanism of action of atosiban?
It is an oxytocin inhibitor
