Uterine Drugs Flashcards
What are the two groups of drugs that affect uterine motility and uterine smooth muscle control?
osytocics
tocolytics
(tokos means childbirth)
What are the three classes of oxytocics?
oxytocin
prostaglandins
ergots
What are the 4 classes ot tocolytics?
beta agonists
magnesium sulfate
oxytocin receptor angatonist
NSAIDs
What do oxytocics do?
stimulate uterine smooth muscle to contract
What do we use them for?
- induce/augment labor
- control postpartum heorrhage
- correct postpartum uterine atony
- produce uterine contractions after c section or other uterine surgery
- expel conceptus
- can initiate and enhanc erhythmic uterine contraction at any time, but relatively high doses are required for such responses in early pregnancy
What do tocolytics do?
suppress uterine smooth muscle and thereby suppress premature labor
Oxtocin is very similar to what other hormone?
ADH - it’s only two amino acids different
Where is Oxytocin made?
paraventricular and supraoprtic nuclei of hypothalamus
What will it be release in response to?
cervical dilation
mechanical stimulation of vagina and uterus
suckling reflex
Describe the oxytocin receptor?
G protein coupled to phosphpolipiase C
Where in the body is the OT receptor?
myoepithelial cells of mammary gland
pregnant myometrium
CNS
What does ethanol do to oxytocin?
inhibits it
What does oxytocin promote?
uterine contraction
milk let-down
antidiuretic and vasoactive at high concentrations
How can we give oxytocin?
parenteral, sublingual or nasal (it’s a peptide)
When in pregnancy is oxytocin degraded more readily?
term
Where in the body os oxytocinase located?
uterus and placenta
What is the synthetic oxytocin?
pitocin
When might you want to speed up labor with pitocin?
chrnic hypertension or preeclampsia
Besides starting and speeding up labor, why do we use it in parturition?
mild let down
stimulation of uterine motility postpartum to reduce bleeding (get uterus to contract back down)
WHat are the contraindications for pitocins?
if baby is too big to pit or presenting breech
also if you have hyperotnic uterine contractions
also in women who ahve had lots of previous c sections - increased risk of uterine rupture
What does PGE2 do?
contracts the uterus and produces hyperalgesia
promotes softening of the cervix
What type of receptor is PGER?
Gs coupled
What does PGF2 do in this regard?
uterine contractions
What type of receptor is the PGFR?
Gq stimulating IP3
What happens to levels of prostaglandins during parturition?
increase in amniotic fluid
What drug will reduce the oxytocin-induced uterine contractions through it’s action on reducing PG production?
indomethacin - an NSAID that blocks COX, so no prostaglandin synthesis
What is the natural PGE we use?
Dinoprostone
What is the synthetic PGE we use?
Misoprostol
Which one can be used as an abortifacient?
Misoprostol
What is the natural PGF2alpha?
Dinoprost
What is the synthetic PGF2alpha used IM
Carboprost
Which trimester can Carboprost be used as an abortifacient or to induce labor?
can be used in any trimester
Which analog is also used to treat hydatidiform mole?
dinoprostone
What are the side effects of these prostaglandin analogs?
basically flu-like symptoms
What are ergots?
alkaloids identified from a fungus that grows on cereal grasses
What will poisoning with ergot cause?
vascular constriction with gangrene in periphery
convulsions
In general, what do the ergots do to smooth muscle?
smooth muscle constriction
Why do we use ergots in this setting?
contraction of the uterus to control postpartum bleeding
Which ergot is largely used for this purpose?
ergonovine = ergometrine
Which ergot is used to contract blood vessels and treat migraine headache?
ergotamine
Which beta2 agonist do we use to slow down uterine contractions?
terbutaline
How does terbulatine work here?
activates the Gs receptor, which activates AC and increases cAMP to turn on PKA.
PKA will turn off myosin light chain kinase, which will decrease muscle contraction
When can terbutaline be used in pregnancy?
after the 2oth week
What are the side effects of tocolytics?
tachycardia and pulmonary edema
also hyperglycemia
can precipitate myocardial infarction by increasing oxygen demand (through increased heart rate)
How is magnesium sulfate given?
IV
What does magnesium sulfate do here?
it competes with calcium and relaxes smooth muscle
Why do we give magnesium in eclampsia?
prevents the seizures
What is the oxytocin receptor antagonist?
Atosiban (Tractocile)
Which has more maternal side effects - atosiban or terbutaline?
terbutaline
but atosiban might not be as effective
