Uterine Stimulants

• Not effective orally

• IV: for initiation and augmentation of labor

• IM: control of postpartum bleeding

• Nasal spray: for impaired milk ejection

Uterine Stimulants

• Given only when cervix is soft and dilated

• 3rd stage of labor

• Control post-partum bleeding

• Effect is dependent on the presence of estrogen

Uterine Stimulants

• __________ uterus is resistant to oxytocin

Uterine Stimulants

Adverse Effects

• Uterine rupture

• Water intoxication (at high concentrations)

• Fetal death

• Maternal death from hypertension

Uterine Stimulants

Contraindications to oxytocin use

Uterine Stimulants

• Produced by Claviceps purpurea fungus

• Induce tetanic contraction (without relaxation)

• Causes contraction of uterus as a whole including fundus and cervix (this tends to compress the fetus rather than expel)

• Given parenterally and orally

• Onset of action: 5-15 minutes

• Duration: up to 3 hours

Uterine Stimulants

Ergot alkaloids

• More selective than other ergot alkaloids in affecting the uterus

Uterine Stimulants

• Should never be given before delivery; given at the time of delivery of placenta

Adverse Effects

• GI upset: nausea, vomiting, diarrhea

• Leg cramps

• Difficulty in breathing

• Overdose: St. Anthony’s Fire → Prolonged vasospasm (pain and gangrene of limbs)

Uterine Stimulants

Contraindications to use of ergot alkaloids

Uterine Stimulants

Prostaglandin Derivatives

• Brand name: Prostin E2

• Synthetic preparation of PGE2 (synthetic according to Katzung, but “naturally occurring” according to slides)

• Administered vaginally for oxytocic use

• Stimulates contraction throughout pregnancy and softens cervix by affecting collagenase

• Approved in USA for abortion in 2nd trimester (12 to 20 weeks), for missed abortion, for benign H. mole, and for ripening of cervix to induce labor near or at term

Uterine Stimulants

Prostaglandin Derivatives

• Brand name: Hemabate

• PGF2a analogue

• Single 250 mcg IM

• Used to induce 2nd trimester abortions and to control postpartum hemorrhage that is not responding to conventional management

Uterine Stimulants

Prostaglandin Derivatives

• Brand name: Cytotec

• PGE1 synthetic analogue (PGE1 according to Katzung and other sources, but “PGE2” in lecture slides)

• Cervical ripening agent

• For treatment of peptic ulcer disease (acts as cytoprotectant; hence, “Cytotec”)

Uterine Stimulants

Adverse Effects

• GI disturbances

• Transient fever

• Headache

• Decreased diastolic BP

• Retained placental fragments

Precautions

• Asthma

• Hyper/hypotension

• DM

• Cervicitis

Uterine Relaxants

• Peptide analogue of oxytocin

• Very short half-life (15 minutes)

• Oxytocin receptor antagonist

• Tocolytic

• Approved for use as a treatment of preterm labor

• Used to inhibit uncomplicated premature labor between 24 and 33 weeks of gestation

Uterine Relaxants

Adverse Effects

• Nausea and vomiting

• Headache and dizziness

• Tachycardia and hypertension

• Hyperglycemia

Uterine Relaxants

• Selective B2 agonist

• Binding to beta receptors activates adenylyl cyclase increasing cAMP & decreasing Ca

• Tocolytic

• Smooth muscle relaxant

• Effective at 20-36 weeks

Uterine Relaxants

Adverse Effects

• Tremors

• Tachycardia at high dose

• Hypotension

• Hyperglycemia

• Hypokalemia

Uterine Relaxants

• Selective B2 agonist

• Interferes with calcium uptake by myometrial cells

• Effective inhibitor of uterine contraction

• Prevents convulsion in preeclampsia

• Preferred over beta agonists in patients with heart disease, DM, hypertension, and hyperthyroidism

Uterine Relaxants

Adverse Effects

• Nausea, vomiting

• Hot flushes

• Nystagmus

Toxicity

• Respiratory depression

• Cardiac arrest

• Loss of patellar reflexes

*Close monitoring is required

Uterine Relaxants

• Selective B2 agonist

• Cyclooxygenase inhibitors (NSAIDs especially Indomethacin)

• Delays preterm labor

• Used in gestation prior to 34 weeks

Uterine Relaxants

Adverse Effects

• Premature closure of ductus arteriosus

• Increased risk of pulmonary hypertension

• Oligohydramnios

• IVH