Uterine Stimulants/Uterine Motility Drugs (Oxytocics)

Uterine motility medications trigger uterine contractions to facilitate labour (oxytocics) or to induce abortion (abortifacients).

Oxytocics

Oxytocics promote uterine muscle contraction, mimicking the action of the hypothalamic hormone oxytocin, which is stored in the posterior pituitary gland.

These medications include:

• Ergonovine (Ergotrate)

• Methylergonovine (Methergine)

• Oxytocin (Pitocin, Syntocinon)

Oxytocin

• Legal Class: Class B controlled drugs

• Medical Class: Oxytocic medication

• Form: Sterile solution for injection

• Strength: 10 IU per ampule

Indications of Oxytocin

1. Labour induction

2. Intrauterine fetal demise cases

3. Hypotonic uterine contractions (weak contractions)

4. Mothers experiencing hypertension

5. Postpartum to manage bleeding

6. Pre-eclampsia and eclampsia conditions

7. Congestive heart failure

8. Post-term pregnancy

9. Prevention of Postpartum Hemorrhage (PPH)

10. Incomplete or missed abortion

11. Active management of the third stage of labour

Contraindications of Oxytocin

• Hypertonic uterus (excessively contracted uterus)

• Fetal and maternal distress

• Multiple pregnancy

• Trial of labour situations

• Malpresentations such as breech or brow

• Cephalo-pelvic disproportion (baby’s head too large for pelvis)

• Low blood pressure

Dose

1. For Labour Induction/Augmentation: 5 I.U. in 500ml of solution for IV infusion, begin at 5 drops per minute initially.

2. For PPH Prevention after Placenta Delivery: Administer 5 I.U. slow IV, increase the rate during the 3rd stage of labour.

Route

• Intramuscular (IM)

• Intravenous (IV) when mixed with normal saline or dextrose

Side Effects

• Dizziness

• Nausea and vomiting

• Skin rashes

• Fetal bradycardia (slow fetal heart rate)

• Hypotension (low blood pressure)

Adverse Effects

• Risk of ruptured uterus

• Hypertension (high blood pressure)

• Tachycardia (fast heart rate)

• Intrauterine fetal hypoxia and anoxia leading to birth asphyxia (oxygen deprivation to the fetus)

Pharmacokinetics

• Absorption is rapid after IV injections.

• Drug distributes through extracellular fluid, with some amount reaching fetal circulation.

• Metabolism occurs quickly in the kidney and liver in small quantities and is excreted via urine.

Abortifacients

Abortifacients are employed to evacuate uterine contents by causing strong uterine contractions.

These drugs include:

• Misoprostol

• Carboprost (Hemabate)

• Dinoprostone (Cervidil, Prepidil Gel, Prostin E2)

• Mifepristone (Mifeprex)

Misoprostol

• Legal Class: Class B controlled drugs

• Medical Class: Oxytocic drug/ cervical ripening agent

• Form: Tablet

• Strength: 200mcg/ 100mcg tablet

Indications

• Labour induction

• Management of postpartum hemorrhage due to uterine atony (failure of uterus to contract)

• Prior to cervical dilatation procedures

• Intra-uterine fetal death

• Treatment of gastric and duodenal ulcers

Contraindications

• Malpresentation of the fetus

• Placenta previa grade 3 and 4

• Multiparous mothers (women with multiple previous pregnancies)

• Cephalo-pelvic disproportion

• Hypersensitivity to misoprostol

Dose

• For Labour Induction: 100mcg vaginally every 12 hours.

• For NSAID ulcers: 200mcg four times daily.

Route

• Sublingually (under the tongue)

• Rectally

• Vaginally

Side Effects

• Headache

• • Dizziness.

  • Fever.

  • Shivering.

  • Vomiting.

  • Uterine rupture.

  • Fetal distress.

  • Constipation.

  Pharmacokinetics

  Absorbed in the gastrointestinal tract and widely distributed throughout the body. Metabolized in the liver and excreted in urine.

  DINOPROSTOL

  • Available Preparation: 3mg tablet.

  • Brand Name: Prostin.

  Pharmacokinetics

  Following vaginal insertion, it diffuses gradually into the maternal bloodstream. Local absorption into the uterus occurs via the cervix. It is broadly distributed in the mother, metabolized in organs such as lungs, liver, kidney, and spleen, as well as other maternal tissues. Excretion is primarily in urine, with a small amount eliminated in feces.

  Indications

  • Induction of labour.

  • Management of missed abortion.

  Contraindications

  • Active cardiac diseases.

  • Multiple pregnancy.

  • Hypersensitivity to dinoprostone.

  • Untreated pelvic infection.

  • Prior Caesarean section.

  Dose

  • 3 mg administered vaginally.

  Side Effects

  • Abdominal pain.

  • Nausea and vomiting.

  • Hypotension.

  • Shivering.

  • Back pain.

  • Rapid cervical dilatation.

  SYNTOMETRINE

  • Legal Status: Class B controlled drugs.

  • Medical Category: Oxytocic drug.

  • Pharmaceutical Form: Sterile solution for injection.

  • Strength: Combination of ergometrine and Pitocin (ergometrine 0.5 mg + Pitocin 5 IU) – available in 1ml ampules.

  Dose

  • 1 ml as a single dose, but can be repeated if necessary when bleeding is uncontrolled.

  Route of Administration

  • Intramuscular.

  • Intravenous.

  Indications

  1. Administration to multi-gravidas post-delivery.

  2. For mothers with a history of postpartum hemorrhage.

  3. In multiple or twin deliveries due to a larger placental site.

  4. For mothers experiencing heavy lochia.

  5. Abortion when the uterine fundal height is less than 12 weeks gestation.

  Contraindications

  Mothers with cardiac disease, pre-eclampsia, eclampsia, and hypertension.

  Adverse Effects

  • Retained placenta.

  • Intrauterine fetal death in undiagnosed second twin.

  • Risk of retaining a second twin.

  • Uterine rupture if given for abortion after 20 weeks of gestation, especially if products of conception are not fully evacuated.

  • Causes hypoxia and anoxia.

  Side Effects

  • Nausea and vomiting.

  • Headache.

  • Hypotension.

  • Dyspnea.

  • Muscle pain.

  ERGOMETRINE

  • Legal Status: Class B controlled drugs.

  • Medical Category: Oxytocic drug.

  • Pharmaceutical Form: Tablet and sterile solution.

  • Strength/Dosage: Tablets ranging from 0.25 to 0.5mg. Injection form: 200mcg/ml, equivalent to 0.5mg/ml.

  EFFECTS

• INDICATION

  (Same as for Syntometrine)

  • For use in mothers who have given birth multiple times, administered post-delivery.

  • In cases of prior postpartum hemorrhage history in the mother.

  • For deliveries involving multiple infants (twins, etc.) due to the expanded placental attachment area.

  • Management of mothers experiencing excessive postpartum vaginal discharge (lochia).

  • For terminating pregnancies when the uterine fundus is less than 12 weeks gestational age.

  Contraindications

  (Same as for Syntometrine)

  Individuals with pre-existing heart conditions, pre-eclampsia, eclampsia, or hypertension are contraindicated for Ergometrine use.

  Side effects

  (Same as for Syntometrine)

  • Feeling of sickness and throwing up.

  • Cephalalgia (head pain).

  • Low blood pressure readings.

  • Breathing difficulty.

  • Muscular pain sensations.

  Dangers

  (Same as for Syntometrine)

  • Possible placental retention post-delivery.

  • Risk of overlooking and retaining a second twin in undiagnosed multiple pregnancies.

  • Potential for uterine rupture if administered for abortion after 20 weeks of pregnancy, particularly if uterine contents are not fully evacuated.

  • May result in fetal oxygen deficiency and complete oxygen deprivation.