Medicines Acting on Uterus

Flashcards about medicines acting on the uterus.

What are myometrial stimulants (uterotonics)?

Medicines that cause uterine contractions or increase the frequency and intensity of contractions.

List examples of myometrial stimulants (uterotonics).

Oxytocin, Ergometrine, Prostaglandin (PG) analogues (misoprostol, Gemeprost, dinoprostone, etc.)

What are myometrial relaxants (tocolytics)?

Medicines that relax the myometrium.

List examples of myometrial relaxants (tocolytics).

Ritodrine, Atosiban.

What are the clinical uses of myometrial stimulants?

Medical abortion, induction and augmentation of labour, prevention of postpartum hemorrhage (PPH), treatment of PPH.

Which medications are FDA-approved for medical abortions?

A combination of misoprostol and mifepristone.

How does pre-treatment with mifepristone facilitate medical abortion?

It sensitizes the uterus to subsequent administration of a PG and therefore abortion occurs in a shorter time and with a lower dose of PG.

What are the formulations of Dinoprostone used for induction and augmentation of labor?

Vaginal tablets, pessaries, gel.

What medications are recommended for the prevention of PPH during the third stage of labor?

Recommended - Oxytocin IV or IM. If oxytocin is unavailable - Ergometrine IM/IV. If skilled birth attendants not available - misoprostol orally.

How is Oxytocin administered for the treatment of PPH?

Bolus followed by infusion.

How is Ergometrine administered for the treatment of PPH?

IM.

What is the mode of action of Oxytocin?

Activation of oxytocin receptors, causes the activation of phospholipase-C b (PLCb), which hydrolyses phosphatidylinositol bisphosphate (PIP2) leading to the formation of two second messengers: Inositol triphosphate (IP3) and diacylglycerol (DAG).

How does oestrogen affect oxytocin sensitivity in the uterus?

Oestrogen induces oxytocin receptor synthesis and the uterus at term is highly sensitive to this hormone.

What are the unwanted effects of Oxytocin?

Nausea, vomiting, headache, rash, arrhythmia; Dose related hypotension and reflex tachycardia; Water retention and Hyponatraemia; Hypertonic uterus and uterine rupture; Anaphylactoid reaction.

What are the contraindications for Oxytocin use?

When vaginal delivery is contra-indicated (CPD, Placenta previa, cord prolapse…).

What are the actions of Ergometrine?

Contracts human uterus. If the uterus is inappropriately relaxed: It induces sustained and strong contractions and reduces bleeding from the placental bed.

What is the mode of action of Ergometrine?

Not well understood - Partly acts on 5HT (serotonin) and alpha receptors.

What are the clinical uses of Ergometrine?

Treatment of PPH and Prevention of PPH.

What are the contraindications of Ergometrine?

Pregnancy and labour**, Pre – eclampsia, Severe fibroids, Moderate to severe heart disease, Severe peripheral vascular disease.

What are the unwanted effects of Ergometrine?

Vomiting: by an effect on dopamine D2 receptors in the chemoreceptor trigger zone; Vasoconstriction: increased blood pressure; Angina, CVA, gangrene; Headache.

What are the specific considerations for Ergometrine use?

Multiple pregnancy: May cause death of second fetus due to excessive uterine contractions; IHD, HT, PVD: May be exacerbated by vasoconstriction; Hepatic impairment: Avoid in severe impairment; Pregnancy: Avoid; induces uterine contraction and causes premature or hypertonic labour.

Provide examples of Prostaglandin Analogues and their indications in obstetrics.

Misoprostol, Gemeprost - Medication abortion; Dinoprostone - Induction/augmentation of labour; Carboprost, Dinoprost - PPH due to uterine atony.

What is Mifepristone?

Antiprogestogenic steroid, Sensitize the myometrium for PG induced contractions and ripens the cervix.

Mention some cautions for using Mifepristone.

Asthma, haemorrhagic disorder, anti-coagulant therapy, prosthetic heart valve.

Mention some contraindications for using Mifepristone.

Uncontrolled severe asthma, hepatic impairment, renal impairment, breast feeding.

What are the side effects of Mifepristone?

GIT cramps, uterine contractions, vaginal bleeding, hypersensitivity reactions.

What is the role of myometrial relaxants?

Tocolytic medicines postpone premature labour.

What are Ritodrine/Salbutamol?

Selective beta 2 agonists, Inhibit spontaneous or oxytocin induced uterine contractions.

What is Atosiban?

Oxytocin receptor antagonist.

List other myometrial relaxants.

Nifedipine, Magnesium sulfate, GTN patches.