Common OB Medications Flashcards
What is the trade name of oxytocin?
Pitocin
What is oxytocin used for?
- induction of labor
- control postpartum uterine bleeding
- after suction D & C
What is the mechanism of action of oxytocin?
- indirectly increases intracellular calcium
- directly stimulates the oxytocin receptor on the myometrium
- some antidiuretic effect
In what cases is oxytocin contraindicated?
- fetal distress
- unfavorable fetal positions
- previous uterine rupture
What are the side effects of oxytocin?
- flushing
- brady/TACHYCARDIA
- hyper/hypotension
Oxytocin Dosing
10-40 units in 1000 ml LR
Oxytocin onset and duration
Onset: immediate
Duration: within 1 hour
Oxytocin causes uterine contraction or relaxation?
uterine contraction
How many weeks of gestation does oxytocin work?
does not work until 12-14 weeks of pregnancy
What is the trade name of methylergonovine?
Methergine
Methylergonovine dosing and frequency
0.2 mg IM q 2-4 hours
MAX OF 5 DOSES
Methylergonovine onset and duration
Onset: 2-5 min
Duration: about 3 hours
T/F: methylergonovine can be given IV or IM
false
- methylergonovine can only be given IM, NEVER IV!!!
What drug class does methylergonovine fall under?
semisynthetic ergot alkaloid
How does methylergonovine work?
increases motor activity of the uterus (contraction) by acting directly on smooth muscle to increase tone, rate, and amplitude of contraction
What is the mechanism of action of methylergonovine?
- arterial vasoconstriction by alpha stimulation
- inhibition of endothelial derived relaxation factor release
When is methylergonovine contraindicated?
- severe HTN
- pregnancy induced hypertension (PIH)
- cardiac disease
Methylergonovine causes uterine contraction or relaxation?
uterine contraction
What is the trade name of carboprost?
Hemabate
What are the side effects of carboprost?
- airway constriction and wheezing
- increased CO, BP, PVR (peripheral vascular constriction)
When is carboprost contraindicated?
asthma
- causes airway constriction and wheezing
Carboprost causes increased or decreased temperature? How does this happen?
- increased temperature
- effect on hypothalamic thermoregulation
- can increase temp by 2 degrees
Carboprost can increase temperature by _____ degrees
2 degrees
What is the mechanism of action of carboprost?
- synthetic analogue of prostaglandin F2 that stimulates uterine contraction
- increase of myometrial calcium, stimulates smooth muscle of GI tract to cause diarrhea
How does carboprost stimulate uterine contraction?
it is a synthetic analogue of prostaglandin F2
Carboprost increases ______________ , which stimulates smooth muscle of the GI tract to cause diarrhea
myometrial calcium
Carboprost dosing and frequency
250 mcq IM q 15-45 min
MAX OF 8 DOSES
Carboprost onset and duration
Onset: immediate
Duration: 2 hours
What is the trade name of misoprostol?
Cytotec
What drug class is misoprostol?
synthetic prostaglandin E1
What is misoprostol indicated for?
- uterine atony
- abortions
- cervial ripening
- peptic ulcer disease
Misoprostol Dosing
1-2 tablets buccal (200 mcq each)
What are the possible routes of administration of misoprostol?
- buccally
- rectally
- vaginally (by OB)
Misoprostol onset and half time
Onset: rapid
Half life: 20-40 min
Misopostol has potential to cause __________
diarrhea
What is magnesium sulfate (MgSO4) used for in OB?
- prevent eclamptic seizures (decreases incidence by 50%)
- stop premature labor (tocolytic)
What effect does magnesium sulfate have at the NMJ?
inhibits release of acetylcholine
How does magnesium sulfate work?
- mild vasodilator that decreases uterine activity to increase uterine blood
- dilates liver beds and kidneys to increase function
- decreases SVR
Magnesium sulftate causes uterine contraction or relaxation?
uterine relaxation
Magnesium sulfate potentiates ___________ and _______________
nondepolarizers and depolarizers
What respiratory side effect comes with administering magnesium sulfate?
pulmonary edema
- may be some correlation with chorioamnionitis
Magnesium sulfate dosing
- 4 grams over 20 min
- 2-3 grams/hr infusion
Magnesium sulfate onset and duration
Onset: immediate
Duration: 20-30 min (assuming good renal perfusion)
What do we have to check when administering magnesium sulfate?
- magnesium levels
- deep tendon reflexes
How do you treat magnesium toxicity?
- 1 gram calcium gluconate over 2 min
- fluids
- diuresis
- O2
Magnesium sulfate _____________ (crosses/does not cross) the placenta
crosses the placenta
What effect does magnesium sulfate have on the fetus/neonate?
- respiratory depression
- apnea
- decreased tone
Magnesium sulfate may cause muscle relaxation or contraction?
muscle relaxation (weakness)
What are therapeutic magnesium sulfate levels for use in OB?
4-8 mg/dL
At magnesium level of 5-10 mg/dl, what would you see?
- ECG
- prolonged PR
- widened QRS
What magnesium level would you begin to see decrease in deep tendon reflexes and respiratory depression?
10 mg/dl
What would you expect to see at a magnesium level of 10 mg/dl?
- decreased deep tendon reflexes
- respiratory depression
What would you expect to see in an OB patient with magnesium levels between 4-8 mg/dl?
therapeutic effects
At what magnesium level would you begin to see respiratory arrest and ECG changes from SA/AV conduction?
15 mg/dl
At what magnesium level would you expect cardiac arrest?
25 mg/dl
What treatments may you consider for blood pressure control in parturients?
- labetalol
- hydralazine
- nipride
- nitroglycerine
- volume repletion (decrease ECF)
Labetalol is a _____________ antagonist
alpha and beta antagonist
What effects does labetalol have on the neonate if administered?
- possibly bradycardia
- typically few neonatal complications
Labetalol has a _________ onset
rapid
How does hydralazine work?
potent vasodilator that decreases afterload, PVR, maternal BP, and uterine vascular resistance to increase uterine blood flow
When would you most see decrease in PVR with hydralazine administration?
volume repletion
What are potential side effects of hydralazine?
- maternal tachycardia (reflex sympathetic response to vasodilation)
- vomiting
- tremors
What is nipride used for in OB?
acute hypertensive crisis
How does nipride decrease blood pressure?
potent arteriolar dilator
Nipride has ______ onset and _______ duration
rapid onset and short duration
Maternal/fetal _________________ is a concern with nipride, but can be prevented with low doses at ________________
- cyanide toxicity
- 5-10 mcg/kg/min
What dose should you keep nipride at for OB patients?
5-10 mcg/kg/min
How does nitroglycerine lower blood pressure?
venodilator to decrease cardiac filling pressures by acting on capacitance vessels
The patient may get reflex _______________ when nitroglycerine is used to lower blood pressure
reflex tachycardia
When would volume repletion be considered in OB?
severe pre-eclampsia
How would intravascular volume repletion be beneficial in OB?
- improve the low CO
- normalize right/left cardiac filling pressures
- improve CI
- decrease maternal HR
- decrease SVR and BP
- improve fetal circulation