OBSTETRICAL DRUG REVIEW

Teratogens Definition: A drug, agent, or influence that adversely affects fetal growth, development, or health Benefit-to-Risk Ratio Estimates if the benefit of the medication to the fetus is greater than the known or unknown risk of side effects of the drug on mother and baby

Distribution Not all drugs in breast milk are well absorbed by the neonate Breastfeeding baby ingests only 1-2% of mother’s total dose Most narcotics such as morphine and demerol are not harmful to infants of C-section breastfeeding mothers However, tobacco and alcohol should be avoided as these substances enter breast milk in large doses

Prostaglandins Prostaglandin Gel (Cervidil or Prepidil) -used to “ripen” or soften the cervix prior to induction of labor. May also stimulate uterine contractions Prostin 15M/Carboprost (Hemabate) -used for postpartum hemorrhage. Dose is 250 mcg IM or intramyometrically (directly into the musculature of the uterus) Misoprostol (Cytotec) -used to treat postpartum hemorrhage. Dose is 800 or 1,000 mcg per rectum

Oxytocics: Uterine Stimulants Pitocin (Oxytocin) Uses Before Birth: For induction and augmentation of labor After Birth: Used to prevent postpartum hemorrhage Administered by IV; IM in emergencies Induction: Infuse slowly via pump @ 0.5 mU/min; increase rate every 20-30 minutes until contraction pattern established. Close monitoring of fetal and uterine status is necessary Postpartum: After placental expulsion, mix 20 units in 1,000 mL LR. Bolus immediately after birth then run at 125 mL/hr Side effects: Hypertension; water intoxication (due to anti-diuretic effect); hyponatremia

Oxytocics: Uterine Stimulants Methergine (Methylergonovine) Oxytocic; induces uterine contractions Routinely used for postpartum hemorrhage or postpartum uterine atony 0.2 mg given IM or PO Side effect: Hypertension (therefore not given to patients with preeclampsia)

Tocolytics: Contraction Inhibitor Terbutaline (Brethine) Inhibits contractions by affecting smooth muscle action Used after 20 weeks gestation and up until 34-35 weeks gestation to stop preterm labor/contractions 0.25 mg SQ; usually repeated in 20 minutes. Up to 3 doses if necessary. No oral terbutaline r/t adverse side effects Common side effect is tachycardia. Hold if HR is > 120 bpm!

Tocolytics: Contraction Inhibitor Magnesium Sulfate (MgSO4) Competes with calcium entry into muscle, thus reducing contraction intensity Used to stop preterm labor Therapeutic range 4-7 mEq/L Administered IV; always on a pump Toxic level may occur if renal functioning is poor

Tocolytics: Contraction Inhibitor Indomethacin (Indocin) Non-steroidal, anti-inflammatory used to control preterm labor. Also reduces amniotic fluid in patients with polyhydramnios. Also aids in closing patent ductus arteriosis (PDA) in newborns Anti-prostaglandin; decreases effect of prostaglandin, thus relaxing smooth muscle Has slight anti-coagulant effect so not given to women with bleeding potential or peptic ulcers

Corticosteroid Betamethasone (Celestone) Long-acting corticosteroid Stimulates maturity of fetal lungs and production of surfactant between 28 and 34 weeks to lessen chance of respiratory distress syndrome 12 mg given IM every 24 hours X 2 doses For maximum benefit, the delivery should be delayed for at least 48 hours after administration

Drugs Used in Pre-eclampsia Magnesium Sulfate (MgSO4) Depresses neuromuscular transmission CNS depressant; depresses CNS activity and decreases CNS irritability Prevents seizure or eclampsia Toxic levels can cause respiratory arrest; death Dose: Bolus 4-6 grams/hr; maintenance dose 1-2 grams/hr Critical drip therefore always on a pump!

Narcotic Antidote Naxolone (Narcan) Used to reverse the effects of opioids including respiratory depression, sedation, and hypertension Causes severe withdrawal in substance abusers Do not administer to the newborn of a drug abuser or patients on methadone

Anesthetics or Locals Spinals Epidurals Regional Blocks Generals Marcaine Xylocaine (Lidocaine)

Neonatal Drugs Erythromycin Ophthalmic Ointment Prevents gonorrhea and chlamydia eye infections in the newborn. Parents can refuse Vitamin K Aids with clotting. Parents can refuse Hepatitis B Vaccine (Heptavax) 3-shot series. First dose at birth; second dose a month later followed by last shot at 6 months of age Requires a signed consent! Why? Some parents believe the vaccine will cause autism. Extensive research confirms no relationship