Oxytocin delivery

Oxytocin is contraindicated in patients with known hypersensitivity to the drug, cephalopelvic disproportion, unfavorable fetal position or presentation, in obstetric emergencies, situations of fetal distress when delivery is not imminent, severe toxemia (preeclampsia, eclampsia), hypertonic uterus, during pregnancy (intranasal administration), when there is total placenta previa, or to induce labor when vaginal delivery is contraindicated. Oxytocin is not expected to be a risk to the fetus when administered as indicated. When oxytocin is administered with vasopressors, severe hypertension may occur. 

Oxytocin may be given IM after delivery of the placenta The nurse obtains the blood pressure, pulse, and respiratory rate every 5 to 10 minutes after the drug is administered. The nurse palpates the patient s uterine fundus for firmness and position. The nurse immediately reports any excess bleeding to the primary health care provider. 

Mery J., Brugidou Rabie A. A peptide nucleic acid (PNA) is more rapidly internalized in cultured neurons when coupled to a retro-inverso delivery peptide. The antisense activity depresses the target mRNA and protein in magnocellu-lar oxytocin neurons. Nucleic Acids Res. 

One compound from this series, (10), has been tested in vitro in human myometrium tissue obtained at term following caesarean section and shown to inhibit contractions induced by oxytocin [44] with a pA2 of 7.6. This is one of the first direct indications that the use of an oxytocin antagonist may be of benefit in the treatment of preterm labour in humans. This compound has been extensively studied in the near-term baboon and has been shown to inhibit nocturnal and near-term contractions following an intravenous bolus injection [45]. Further studies on the effect of oxytocin antagonism in the weeks leading up to delivery in the baboon have also been published [46]. 

The IV or IM administration of parenteral narcotics (meperidine, morphine, fentanyl) is commonly used to treat the pain associated with labor. Compared to epidural analgesia, parenteral opioids are associated with lower rates of oxytocin augmentation, shorter stages of labor, and fewer instrumental deliveries. 

Ritodrine relaxes the uterine muscle and is therefore indicated to prevent premature labour. Ergometrine, oxytocin and carboprost are all indicated to induce or augment labour by inducing uterine contractions and hence can be used to cause the uterus to contract after delivery. Dinoprostone is mostly used for the induction of labour. 

Oxytocin also stimulates contraction of uterine smooth muscle in late phases of pregnancy. See Chapter 62 for a full discussion of the use of oxytocin in labor and delivery. 

Because dinoprostone produces cervical ripening along with stimulation of the uterus, it has been used as an alternative to oxytocin for the induction of labor. Preparations of dinoprostone can be placed in either the cervix or the posterior fornix. Prepidil is a formulation and delivery system of dinoprostone that delivers a dose of 0.5 mg into the cervix, while Cervidil consists of the drug embedded in a plastic matrix. The matrix is designed to deliver a dose of 0.3 mg per hour for 12 hours. 

Theoretically, PGE2 and PGF2K should be superior to oxytocin for inducing labor in women with preeclampsia-eclampsia or cardiac and renal diseases because, unlike oxytocin, they have no antidiuretic effect. In addition, PGE2 has natriuretic effects. However, the clinical benefits of these effects have not been documented. In cases of intrauterine fetal death, the prostaglandins alone or with oxytocin seem to cause delivery effectively. 

Oxytocin is a peptide hormone secreted by the posterior pituitary that participates in labor and delivery and elicits milk ejection in lactating women. During the second half of pregnancy, uterine smooth muscle shows an increase in the expression of oxytocin receptors and becomes increasingly sensitive to the stimulant action of endogenous oxytocin. Pharmacologic concentrations of oxytocin powerfully stimulate uterine contraction. 

Oxytocin is used to induce labor for conditions requiring early vaginal delivery such as Rh problems, maternal diabetes, preeclampsia, or ruptured membranes. It is also used to augment abnormal labor that is protracted or displays an arrest disorder. Oxytocin has several uses in the immediate postpartum period, including the control of uterine hemorrhage after vaginal or cesarean delivery. It is sometimes used during second-trimester abortions. 

Before delivery, oxytocin is usually administered intravenously via an infusion pump with appropriate fetal and maternal monitoring. For induction of labor, an initial infusion rate of 0.5-2 mU/min is increased every 30-60 minutes until a physiologic contraction pattern is established. The maximum infusion rate is 20 mU/min. For postpartum uterine bleeding, 10-40 units are added to 1 L of 5% dextrose, and the infusion rate is titrated to control uterine atony. Alternatively, 10 units of oxytocin can be administered by intramuscular injection after delivery of the placenta. 

During the antepartum period, oxytocin induces uterine contractions that transiently reduce placental blood flow to the fetus. The oxytocin challenge test measures the fetal heart rate response to a standardized oxytocin infusion and provides information about placental circulatory reserve. An abnormal response, seen as late decelerations in the fetal heart rate, indicates fetal hypoxia and may warrant immediate cesarean delivery. 

When oxytocin is used judiciously, serious toxicity is rare. The toxicity that does occur is due either to excessive stimulation of uterine contractions or to inadvertent activation of vasopressin receptors. Excessive stimulation of uterine contractions before delivery can cause fetal distress, placental abruption, or uterine rupture. These complications can be detected early by means of standard fetal monitoring equipment. High concentrations of oxytocin with activation of vasopressin receptors can cause excessive fluid retention, or water intoxication, leading to hyponatremia, heart failure, seizures, and death. Bolus injections of oxytocin can cause hypotension. To avoid hypotension, oxytocin is administered intravenously as dilute solutions at a controlled rate. 

Oxytocin Activates oxytocin receptors Increased uterine contractions Induction and augmentation of labor control of uterine hemorrhage after delivery IV infusion Toxicity Fetal distress, placental abruption, uterine rupture, fluid retention, hypotension... 

Misoprostol and oxytocin have been compared in three trials during vaginal and cesarean delivery. The first trial included 663 women (mean age 25 years, mean parity 2)... 

Chelmow D, Laros RK Jr. Maternal and neonatal outcomes after oxytocin augmentation in patients undergoing a trial of labor after prior cesarean delivery. Obstet Gynecol 1992 80(6) 966—71. 

A mucoadhesive buccal patch was evaluated for transmucosal delivery of oxytocin (OT) [103], OT was incorporated with coformulations of Carbopol 974P and silicone polymer. The plasma concentrations of OT remained 20- to 28-fold greater than levels obtained from placebo patches for a period of 0.5 to 3.0 h. 

Li, C., et al. 1997. Transmucosal delivery of oxytocin to rabbits using a mucoadhesive buccal patch. Pharm Dev Technol 2 265. 

Oxytocin is used to induce labor and augment dysfunctional labor for (1) conditions requiring early vaginal delivery (eg, Rh problems, maternal diabetes, or preeclampsia), (2) uterine inertia, and (3) incomplete abortion. Oxytocin can also be used for control of postpartum uterine hemorrhage. 

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