Oxytocin

Initiation of labour , precaution, contraindications

Indications: Premature membrane rupture, Fetal growth restriction, uteroplacental insufficiency, gestation beyone 42 wks

Precautions: Verify lungs are mature

Contraindication: Abnormal fetal position, Fetal distress, placental abnormalities , Previous uterine surgery

Drugs increase uterine motility especially at term

Posterior pituitary hormones: Oxytocin, Desamino oxytocin

Ergot alkaloids: Ergometrine (Ergonovine), Methylergometrine

Prostglandins: PGE2, PGF2a, Misoprostol

Oxytocin (Action)

1. Stimulate uterine contraction to induce/enforce labour

2. Causes mile ejection by contracting myoepithelal cells around mammary alveoli

3. Infused IV, administered IM or delivered intranasally

4. Plasma ½ life of oxytocin is 5-10 mins

Oxytocin (Therapeutic uses)

IV for inducition and maintanence of labour

Nasal spray for stimulate milk let down in mothers

Injected IM to prevent postpartum uterine hemmorage

Oxytocin side effects

uncommon but

Hypertension

Uterine rupture

Water retention and fetal death

Antidiuretic and pressor activites

Oxytocin contraindications and Desamino oxytocin

Contraindication: Abnormal fetal presentation, fetal distress, premature birth

Desamino oxytocin: Oral less consistent (induces labour, uterine inertia and promote uterine involution)

Prostglandins (Names and uses)

PGE2 (Dinoprostone)

PGE1 analogue (Misoprostol) → oral or vaginal to induce cervical ripening (sotening)

PGF2a (Carboprost)

They all are potent stimulation of uterine contractions

1. Induces labor: Dinoprostone (Intravaginal), Carboprost (IM) , Misoprostol ( oral and Intravaginal)

2. Softening cervix (PGE1)

3. Delivery of intrauterine fetus

Prostglandin Adverse effects and contraindications

Adverse effects:

1. Prolonged vaginal bleeding

2. Uterine hyperstimulation

3. Misoprostol should be discontinued for 3hrs before oxytocin therapy (Cervical ripening not good contraction)

Contraindications:

Dinoprostone not used in women with asthma, glaucome or myocardial infarction

Ergot alkoids : Ergometrine and methylergometrine

Powerful oxytocic

• Uterus

1. Ergometrine has faster contraction persist contraction (not suitable for inducing labour) Oxytocin produces slow contraction with full relax between

2. IM ergometrine takes 5 mins while oxytocin takes 1-2 mins tho contraction brief.

• CVS : Can raise BP not enough at obstretic doses

• GIT : High doses increase peristalsis

Therapeutic uses:

1. Primary is control and prevent postpartum hemmorage through increasing uterine muscle tone

2. After C section/ instrument delivery Prevent uterine atony (no contract after birthing)

3. To ensure uterus involution (contraction after birthing to normal position)