Update on tocolytic therapy

The effect of relcovaptan (SR 49059), an orally active vasopressin V1a receptor antagonist, on uterine contractions in preterm labor

Relcovaptan (SR 49059) is a non-peptide, orally active vasopressin V1a receptor inhibitor. The effect on uterine contractions in 18 women with preterm labor in pregnancy weeks 32-36 was assessed in a double-blind investigation. The inclusion criterion was at least four regular uterine contractions over 30 min as measured by external tocodynamometry. Twelve patients received at random a single oral dose of 400 mg relcovaptan and six received placebo, and contractions were monitored up to 6 h thereafter. Rescue medication (beta-adrenoceptor-stimulating drug) was allowed after 2 h. Before drug administration a mean (+/- SE) of 8.2 +/- 1.4 and 9.7 +/- 1.6 contractions/30 min were recorded in the relcovaptan- and placebo-treated groups, respectively. In the former group, the frequency of uterine contractions started to decrease within the first half hour, and 1.5-2 h after dosing it was steady at 3.2 +/- 0.9 contractions/30 min. Correspondingly, after placebo, 7.8 +/- 2.2 contractions/30 min were recorded, a statistically significant difference (p = 0.017). The activity in the relcovaptan-treated women remained low, whereas in the placebo group inhibited uterine contractions were observed only in women receiving 'rescue' tocolytic treatment. It is concluded that relcovaptan inhibits preterm labor.

Evaluación farmacoeconómica de dos protocolos de tocolisis para la inhibición del parto prematuro

OBJECTIVE

Pharmacoeconomic assessment of two tocolysis protocols alternatively using atosiban or ritodrine as first-choice tocolytic agent able to delay birth for 48 hours in the acute management of premature birth risk in gravid women.

METHODS

The modeling technique used for the selection of the most efficient protocol was the decision analysis. A search for controlled clinical trials comparing the effectiveness and/or safety of atosiban versus ritodrine was performed in Medline and the Cochrane Library. Only differential costs were considered for cost analysis.

RESULTS

Cost-effectiveness obtained with the protocol including ritodrine as first-choice drug was Euros 194/effectiveness unit, and Euros 632/effectiveness unit when atosiban is used. The sensitivity analysis shows sensitivity only for an incidence of acute lung edema greater than 8% or a cost of at least Euros 50,000.

CONCLUSION

A tocolysis protocol using ritodrine as first-choice agent and atosiban as rescue drug is the most efficient option based on available evidence. In pregnant women where the likelihood of developing acute pulmonary edema is high, or when therapy cost is high, atosiban may be an appropriate alternative option.

Effect of the antenatal administration of celecoxib during the second and third trimesters of pregnancy on prostaglandin, cytokine, and nitric oxide levels in rabbits

OBJECTIVE

The purpose of this study was to examine the effects of celecoxib on prostaglandin, cytokine, and nitric oxide synthesis in the pregnant rabbit.

STUDY DESIGN

Pregnant rabbits received celecoxib from 13 to 20 days (celecoxib-A), from 13 to 28 days (celecoxib-B), or vehicle from 13 to 28 days by gavage. Blood and tissue were assayed for prostaglandin, cytokine, and nitric oxide oxidation products.

RESULTS

Preterm delivery occurred in 4 of 11 controls, 0 of 9 in celecoxib-A, and 0 of 8 in celecoxib-B. Plasma prostaglandin F(2alpha) was reduced in both treated groups at 20 days and at delivery in celecoxib-B. Plasma thromboxane B(2) was suppressed in celecoxib-B at 20 days and delivery. Cervical prostaglandin E(2) was increased; uterine and cervical plasma thromboxane B(2) declined in celecoxib-B. Celecoxib administration suppressed plasma nitric oxide oxidation products at delivery and cervical nitric oxide oxidation products in celecoxib-B. Uterine and cervical interleukin-1beta and interleukin-6 were decreased, and uterine tumor necrosis factor-alpha increased in celecoxib-B.

CONCLUSION

Further studies are required to evaluate the therapeutic benefits of cyclo-oxygenase-2 inhibitors in the setting of preterm parturition.

Effect of maternal tocolysis on the incidence of severe periventricular/intraventricular haemorrhage in very low birthweight infants

AIM

To examine the relation between grade III-IV periventricular/intraventricular haemorrhage (PVH/IVH) and antenatal exposure to tocolytic treatment in very low birthweight (VLBW) premature infants.

STUDY DESIGN

The study population consisted of 2794 infants from the Israel National VLBW Infant Database, of gestational age 24-32 weeks, who had a cranial ultrasound examination during the first 28 days of life. Infants of mothers with pregnancy induced hypertension or those exposed to more than one tocolytic drug were excluded. Of the 2794 infants, 2013 (72%) had not been exposed to tocolysis and 781 (28%) had been exposed to a single tocolytic agent. To evaluate the effect of tocolysis and confounding variables on grade III-IV PVH/IVH, the chi(2) test, univariate analysis, and a logistic regression model were used.

RESULTS

Of the 781 infants (28%) exposed to tocolysis, 341 (12.2%) were exposed to magnesium sulphate, 263 (9.4%) to ritodrine, and 177 (6.3%) to indomethacin. The overall incidence of grade III-IV PVH/IVH was 13.4%. In the multivariate logistic regression analysis, the following factors were related significantly and independently to grade III-IV PVH/IVH: no prenatal steroid treatment, low gestational age, one minute Apgar score 0-3, respiratory distress syndrome, patent ductus arteriosus, mechanical ventilation, and pneumothorax. Infants exposed to ritodrine tocolysis (but not to the other tocolytic drugs) were at significantly lower risk of grade III-IV PVH/IVH after adjustment for other variables (odds ratio = 0.3; 95% confidence interval 0.2 to 0.6).

CONCLUSION

This study suggests that antenatal exposure of VLBW infants to ritodrine tocolysis, in contrast with tocolysis induced by magnesium sulphate or indomethacin, was associated with a lower incidence of grade III-IV PVH/IVH.

Controversies in tocolytic therapy

In general, tocolytic agents are effective in stopping uterine contractions and in temporarily delaying delivery. The benefit of stopping uterine contractions is dependent on the fetal status and gestational age. The rationale for stopping preterm labor is to improve neonatal outcome. At this time, the best way to improve neonatal outcome would be to assure delivery in a center capable of caring for a preterm infant and prescription of glucocorticoids to decrease the risk of respiratory distress syndrome and other neonatal complications. Intravenous tocolysis for premature labor has found a prominent place in the obstetrician's armamentarium. We recommend the use of magnesium sulfate as first-line therapy. When comparing maternal and fetal risks, side effects, and the safety profile, magnesium sulfate is superior to beta-mimetics; however, there are still significant problems with potential morbidity and mortality for both mother and fetus with any tocolytics. Adjunctive use of indomethacin with magnesium sulfate may be used through 32 weeks for up to 48 hours at a time. Most tocolytics are effective in stopping labor for 48-72 hours. None have been shown to decrease the rate of preterm delivery. Once the uterus is quiescent and intravenous tocolytics are stopped, prolonged use of tocolytics has not been shown to be effective in preventing preterm birth. Tocolytics have significant long-term side effects to the mother's cardiovascular system, carbohydrate metabolism, and the fetal cardiovascular system. Thus, the prolonged use of prophylactic tocolytics after cessation of intravenous medications is not recommended. Tocolytics may be an appropriate therapy during preterm labor vaginal bleeding, ruptured membranes, multiple gestation, or advanced cervical dilatation. In all situations, however, careful guidelines must be observed. These guidelines include: (1) maternal and fetal well-being must be established before tocolytic therapy; (2) causes of preterm labor should be evaluated and treated when possible; (3) the risk/benefit ratio for both the mother and fetus must be re-evaluated on an ongoing basis; (4) when tocolytics are given before pulmonary maturity, then antenatal corticosteroids also should be considered in every case; (5) long-term use of tocolytics is difficult to justify at this time; (6) the safest tocolytic should be used for the shortest amount of time possible. It is doubtful, because of the nature of tocolytics, that newer tocolytics will be developed that will eliminate the problems of preterm delivery. Preterm delivery is an end-stage symptom of a multifactorial disease. Preterm labor is one of the last symptoms in a cascade of biochemical events that lead to preterm delivery. The most appropriate way to end preterm delivery would be to prevent the causes that initiate the cascade that ends in preterm labor. Authors' Note: Literally hundreds of papers have been written in the last 30 years on tocoloysis. For the purposes of space, when studies are summarized in peer-reviewed articles, we have referenced the reviews instead of the individual studies.

Clinical issues surrounding the use of terbutaline sulfate for preterm labor

beta-mimetics have been prescribed by physicians to arrest or prevent premature labor for more than 20 years. Although not approved by the Food and Drug Administration (FDA) for tocolytic use, terbutaline sulfate has been the most widely prescribed beta-mimetic in the United States. Recently, the role of terbutaline in the treatment and prevention of preterm labor has been questioned by the FDA. Because the off-label use of drugs is a formally accepted practice in medicine when scientific studies support such use, we reviewed the currently available clinical literature on terbutaline use in various routes of delivery: intravenous, oral, and subcutaneous via infusion pump. This review describes the clinical evidence that supports the safe and effective use of terbutaline as a tocolytic agent in certain patient populations. Practicing physicians should continue to have unrestricted use of terbutaline for tocolysis as one of the few remaining therapeutic options remaining in the fight against preterm birth.

Medication use during the perinatal period

OBJECTIVE

To briefly describe the drug therapy administered during the perinatal period of pregnancy for common maternal and fetal complications, and to identify those agents that should not be used for these conditions.

DATA SOURCES

References were obtained from an ongoing literature search of peer-reviewed obstetric and gynecologic journals and other selected medical and pharmacy journals available in the English language. Primary search vehicle was a weekly review of the tables of contents of nearly 1,300 medical journals provided by Reference Update (Institute of Scientific Information, Philadelphia). MEDLINE searches were also conducted using key terms for each subtopic.

STUDY SELECTION

Specific references were selected for each topic based on the adequacy of their study design, patient population, and a recent publication date. Reviews were used if a large number of primary references would have been required to adequately describe the topic.

DATA EXTRACTION

Most references reflected the current opinions expressed in the Educational (Technical) Bulletin and Committee Opinion series published by the American College of Obstetricians and Gynecologists. Recent, well-conducted studies that arrived at different conclusions were also included.

DATA SYNTHESIS

Data obtained from each reference reflected the conclusions of the authors based on their research or an analysis of the research on others on the appropriate use of the drug(s) for the specific condition being treated.

CONCLUSION

Drug therapy during the perinatal period is frequently required and can be beneficial for the mother, fetus, and newborn. Many complications previously associated with severe morbidity and mortality, such as infections, premature rupture of membranes, preterm labor, hypertension, maternal pain during labor, and postpartum hemorrhage, are now controlled with appropriate pharmacologic therapy. All health professionals who provide services to pregnant women should be knowledgeable in this drug therapy.

Are alpha-adrenergic antagonists potent tocolytics? In vivo experiments on postpartum rats

The aim of this study was to investigate the effects of alpha-adrenergic antagonists on the motor activity of the postpartum uterus of the rat in vivo. Intrauterine pressure was assessed by means of a Millar catheter fitted with a latex microballoon. Some of the tested compounds (urapidil, yohimbine, phentolamine, benoxathian and prazosin) decreased the uterine activity to a significant extent (57.4-67.4%). However, none of the investigated alpha receptor blockers exerted the same effect as beta-adrenergic agonists. Our results suggest that alpha-adrenergic antagonists could possibly be used as an alternative to beta-adrenergic agonists in clinical tocolysis after an appropriate clinical evaluation.

Cardiopulmonary Adverse Effects of Oral and Subcutaneous Terbutaline for Tocolysis

Are there differences between the expected or reported adverse reactions associated with terbutaline when administered orally as opposed to the parenteral routes (such as subcutaneously or intravenously)? This is a report on a pulmonary edema and subsequent death of a laboring woman who was treated with a combination of tocolytic agents in an attempt to prolong the gestation. The agents included magnesium sulfate, and subcutaneous and oral terbutaline. The intention is to alert the reader to the cardiovascular risks associated with combining tocolytic agents, and to dispel a pervasive myth that serious adverse reactions do not occur with oral tocolysis (i.e., terbutaline).1 Until recently, the package insert sheets for both manufacturers of terbutaline restricted the attribution of serious cardiovascular risks to parenteral administration only. The clinical case will be presented, followed by a review of the published literature and the reports on file in the unpublished Food and Drug Administration MedWatch database. Finally, the comparative pharmacokinetics of the oral and parenteral terbutaline is presented to help the reader understand how these adverse events are to be expected with any route of administration of the tocolytic.