Chapter 64
Drugs That Affect Uterine
Function
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
Drugs That Affect Uterine Function
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Three main categories:
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Uterine relaxants (tocolytics)
• Uterine relaxation
• Suppression of preterm labor
Uterine stimulants (oxytocics)
• Uterine contraction
• Induction/augmentation of labor
• Control of postpartum bleeding
• Induction of abortion
Drugs used to decrease menorrhagia (heavy
menstrual bleeding)
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Preterm Birth
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Before 37 weeks’ gestation
Leading cause of infant morbidity and
neonatal mortality
United States: 12.5% of all live births
Premature births account for 75% of all
neonatal mortalities and 50% of congenital
neurologic deficits
Most common neonatal respiratory distress
syndrome
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Relaxants (Tocolytics)
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Used to delay delivery
Average delay: only 48 hours
If used with glucocorticoids, the
glucocorticoids can accelerate lung
development
Also used to buy time to treat infection
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Control of Myometrial Contraction
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Regulated by multiple mediators
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Beta-adrenergic agonists
Oxytocin
Prostaglandins
Four classes of drugs: all decrease the
availability of phosphorylated light chain
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Beta-adrenergic antagonists, calcium channel
blockers, cyclooxygenase (COX) inhibitors, and
oxytocin-receptor antagonists
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Relaxants (Tocolytics)
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Beta2-selective adrenergic agonist
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Terbutaline (Brethine)
• Beta2-selective adrenergic agonist
• Not approved by FDA for this use
Nifedipine (Procardia, Adalat, Nifedical)
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Can suppress labor for up to 48 hours
Efficacy equals that of terbutaline, and safety is
superior
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Relaxants (Tocolytics)
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Indomethacin (Indocin)
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Second-line tocolytic
Higher risk for neonatal complications
Prolonged renal insufficiency, bronchopulmonary
dysplasia, necrotizing enterocolitis, and
periventricular leukomalacia
Nitroglycerin, a nitric oxide donor
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Relaxants (Tocolytics)
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Atosiban
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Oxytocin: receptor antagonist
Magnesium sulfate
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High dose does not prevent or delay preterm birth
but does increase infant mortality
Was previously used readily
Low-dose magnesium sulfate may reduce the risk
of cerebral palsy without increasing mortality
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Drugs Used to Promote
Cervical Ripening
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Dinoprostone (Prepidil, Cervidil)
Dinoprostone gel
Dinoprostone vaginal inserts (Cervidil)
Misoprostol (Cytotec)
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Not approved for this use
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Stimulants (Oxytocics)
Prostaglandins: Dinoprostone and Misoprostol
(can also induce labor)
 Dinoprostone
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Most widely used for cervical ripening
Shortens duration of labor, allows reduced dosage
of oxytocin, decreases need for cesarean section
Can also induce abortion
Misoprostol
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Not approved for cervical ripening
More convenient and less expensive than
dinoprostone
 Higher incidence of uterine tachysystone
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Stimulants (Oxytocics)
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Three groups of uterine stimulants
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Oxytocin
Ergot alkaloids
Prostaglandins
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Stimulants (Oxytocics)
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Oxytocin (Pitocin)
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Peptide hormone produced by the posterior
pituitary
 Increases the force, frequency, and duration of
uterine contractions
 Uterus becomes progressively more responsive to
oxytocin throughout pregnancy
 Facilitates labor, but unclear whether it can initiate
labor
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Stimulants (Oxytocics)
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Oxytocin (Pitocin) (cont’d)
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Physiologic and pharmacologic effects
• Uterine stimulation
• Milk ejection
• Water retention
Precautions and contraindications
• Uterine rupture may occur
• Women with active genital herpes
Adverse effect: water retention/intoxication
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Stimulants (Oxytocics)
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Ergot alkaloids: ergonovine and
methylergonovine
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Dried preparation of Claviceps purpurea
Stimulate adrenergic, dopaminergic, and
serotonergic receptors
Not used to induce labor (sustained contractions)
Can cause constriction of arterioles and veins and
risk of severe hypertension
Used to control postpartum bleeding
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Stimulants (Oxytocics)
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Ergot alkaloids: ergonovine and
methylergonovine (cont’d)
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Therapeutic uses
• Postpartum bleeding (not responsive to oxytocin and
carboprost tromethamine)
• Augmentation of labor
• Migraine
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Adverse effects (IV administration)
• Hypertension
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Uterine Stimulants (Oxytocics)
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Carboprost tromethamine (Hemabate)
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Preferred agent for controlling postpartum
hemorrhage
 Causes intense uterine contractions
 Adverse effects
• GI reactions
• Vomiting and diarrhea
• Fever
• Vasoconstriction
• Constriction of the bronchi
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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Drugs for Menorrhagia
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Tranexamic acid
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Menorrhagia
Trauma patients
Adverse effects and interactions
NSAIDs
Combination oral contraceptives
Levonorgestrel-releasing intrauterine system
Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.
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