Magnesium sulfate and ritodrine hydrochloride: a randomized comparison

The efficacy of magnesium sulfate was analyzed in relation to ritodrine hydrochloride. Patients presenting in preterm labor between 20 and 35 weeks' gestation were prospectively randomized. Tocolysis was achieved for more than 72 hours in 35 of 40 cases (88%) where magnesium sulfate was administered and 31 of 39 cases (79%) in which ritodrine hydrochloride was infused. Delay of greater than or equal to 7 days was achieved in 75% and 72% of cases, respectively. The mean dosage to achieve tocolysis was 4.5 gm/hr, in the magnesium sulfate group and 210.0 micrograms/hr in ritodrine hydrochloride-treated patients. The mean magnesium level to achieve tocolysis was 6.60 mg/dl. Side effects in the two groups were similar in number but less alarming in the magnesium sulfate group. Magnesium sulfate was found to be easy to administer and clinically efficacious. Its tocolytic action was found to be dose dependent and drug concentrations are easily determined. On the basis of this work and data from other investigators, magnesium sulfate should be used as the first line of tocolytic therapy with ritodrine hydrochloride as its pharmacologic backup.

Drug-induced pulmonary disease

Administration of more than 40 separate pharmacologic agents has been associated with some form of pulmonary toxicity. This problem is becoming more significant every year. Occasionally, effective modes of therapy must be withdrawn because of undesirable pulmonary side effects, putting patients at risk for potentially lethal diseases. Pulmonary parenchymal damage due to drugs is an especially troublesome problem because irreversible pulmonary disease may occur. Mechanisms of pulmonary parenchymal tissue damage by drugs are unclear. It appears that some drugs induce direct tissue injury in addition to indirect tissue damage through amplification of pulmonary inflammation; other drugs cause pulmonary alterations solely through indirect mechanisms. Common clinical syndromes associated with drug-induced pulmonary parenchymal disease include pneumonitis/fibrosis, hypersensitivity lung disease, and noncardiogenic pulmonary edema. Less common patterns of pulmonary parenchymal injury by drugs include bronchiolitis obliterans and a pulmonary renal syndrome. Risk factors for pulmonary injury due to pharmacologic agents are partially defined but not entirely understood. To date, there are no adequate tests for early detection of pulmonary damage by drugs, although research into this area is active. This review discusses mechanisms and clinical features of drug-induced pulmonary parenchymal injury to aid the clinician in recognizing and understanding these syndromes.

Effect of antepartum ritodrine on the cardiorespiratory status of the newborn after elective cesarean section

Heart rate (HR), heart rate variability (HRV), respiratory rate (RR) and transcutaneous PO2 and CO2 of 12 infants born by elective cesarean section were monitored during the first postnatal hour in order to evaluate the effect of the beta-mimetic tocolytic drug ritodrine. Six of the mothers received ritodrine by infusion and the other 6 physiological saline during the 2 h prepartum. The Apgar scores of the treatment group were higher (p less than 0.05) but there was a significant increase in RR (p less than 0.05) during the first hour in these babies. Arterial blood pressure (BP) was lower in the group whose mothers had received ritodrine (p less than 0.05) but there was no difference in pulse pressure. Transcutaneous pressure of CO2 (PtcCO2) of the controls decreased during the first hour (p less than 0.05). Transcutaneous pressure of O2 (PtcO2) increased during the first postnatal hour (p less than 0.01) when both groups were examined together. HR of both groups was relatively high and HRV low.

Neonatal complications following in utero exposure to intravenous ritodrine

Intravenous administration of ritodrine for tocolysis has been associated with maternal cardiovascular and metabolic changes. Studies with other tocolytic agents, such as isoxsuprine, have shown an increased neonatal morbidity among infants born soon after failure of such therapy. We examined the potential side effects of maternal intravenous ritodrine therapy in 58 neonates born within 12 h following discontinuation of maternal medication. 'Low dextrostix' was significantly greater in the ritodrine exposed neonates (p less than 0.05) than in the controls. It occurred within a mean 1.0 +/- 0.5 h following birth. The mean 1 min and 5 min Apgar scores, neonatal pH, bicarbonate levels, hypotension and neonatal mortality were comparable in the ritodrine-exposed and control groups of neonates. The occurrence of any of the neonatal morbidity variables, including 'low dextrostix' was not related either to the total dose of ritodrine used or to the interval between drug discontinuation and delivery. Administration of ritodrine by the standard protocol to stop preterm labor is not associated with any significant increase in neonatal morbidity.

A study of maternal ECG characteristics before and during intravenous tocolysis with beta-sympathicomimetics. Effects of i.v. tocolysis on maternal ECG characteristics

Severe maternal complications during beta-mimetic therapy have been reported. In a study of maternal complications related to intravenous tocolysis, which covering a period of 2 years, we paid special attention to the maternal ECG before and during treatment. There was a high prevalence of pretreatment ECG changes: tachycardia (23.6%), disorders of impulse conduction (43.6%), ST-depression (14.5%) and disorders of repolarization (43.6%). During intravenous beta-mimetic therapy there was an increase in the prevalence of tachycardia, prolonged QT-time and disorders of repolarization. We also studied the course in time of the different ECG characteristics during treatment. With regard to the ST-depression, a possible physiological adaptation to the beta-mimetic drug is described. We could not find this possible adaptation with regard to the other ECG characteristics. None of the women in the studied group showed clinical signs of myocardial ischemia, notwithstanding the high prevalence of ECG changes. We conclude that the ECG criteria for discontinuation of tocolytic therapy need re-evaluation.

Ventricular septal thickness and cardiac function in neonates after in utero ritodrine exposure

Cardiac septal hypertrophy occurs after in utero ritodrine exposure. To assess the effect of septal hypertrophy on cardiac function we obtained M-mode echocardiograms on day 1 of life in 41 infants exposed to ritodrine and 22 control infants matched for gestational age. Mean duration of ritodrine exposure was 16.2 +/- 13.2 days (range 1 to 49 days). Disproportionate septal hypertrophy (DSH) was defined as an interventricular septal thickness/posterior wall thickness ratio (ST/PW) of greater than 1.3. Infants exposed to ritodrine in utero had DSH and increased right systolic time intervals compared with control values (P less than 0.05). A subgroup, those infants exposed for 2 weeks or longer, had not only DSH but also an absolute increase in septal thickness compared with control infants and infants exposed to ritodrine for less than 2 weeks. ST/PW correlated well with the duration of ritodrine exposure (r = 0.96); the longer the exposure the thicker the septum. Although all echocardiographic changes lasted for less than 3 months, we have no information regarding the effect on the fetus of maternal ritodrine exposure for longer than 7 weeks. Until such information is available, cardiac evaluation is recommended in neonates exposed to ritodrine in utero for longer than 7 weeks.

Elevated serum transaminase levels during ritodrine administration

Two cases are presented of the occurrence of elevated serum transaminase levels during ritodrine administration for the treatment of premature labor. The clinical course of these cases suggests that elevated transaminase levels per se do not require the discontinuation of beta-sympathomimetic tocolytic treatment.

Ritodrine in the treatment of preterm labor: second Danish Multicenter Study

In a randomized trial intramuscular ritodrine followed by oral ritodrine treatment and bed rest was compared with placebo and bed rest in the treatment of 99 cases of preterm labor. The ritodrine treatment did not have a statistically significant effect on birth weight, gestational age, or the incidence of low birth weight. However, it did inhibit preterm labor in the initial stage, resulting in a gain of a few days to a few weeks in length of gestation. This gain may be valuable. Where necessary, advantage can be taken of it to transfer the mother before delivery to a more specialized hospital with a neonatal intensive care unit or to administer steroid treatment to promote fetal lung maturation. No serious side effects were recorded. The intramuscular route is recommended because large fluid infusions are avoided and treatment can easily be started before the patient is transported from home to hospital.

Ritodrine-induced neutropenia

Ritodrine hydrochloride, a beta-sympathomimetic treatment for premature labor, has been associated with the development of pulmonary edema, various metabolic derangements, myocardial ischemia, and infarction. We present the first reported case of absolute neutropenia after prolonged intravenous administration of ritodrine with rapid, spontaneous reversal once the medication was discontinued.

Electrocardiographic changes associated with ritodrine-induced maternal tachycardia and hypokalemia

One hundred twelve patients in preterm labor were followed prospectively, with electrocardiograms taken before ritodrine therapy and at 6 and 24 hours of treatment. Ninety-six percent of patients developed sinus tachycardia. Other changes were seen in 79% of the study group. These changes included ST segment depression in 70%, T wave flattening or inversion in 55%, and prolongation of the QT interval in 35% of our sample. None of the electrocardiograms showed the presence of a significant axis deviation, a change in QRS interval, or arrhythmia. No correlation was seen between symptoms of ischemia and electrocardiographic changes. A drop in potassium concentration was noted initially, but a direct correlation between potassium concentrations and frequency of electrocardiographic changes was not present. We conclude that the electrocardiographic changes that are often observed during myocardial ischemia may be frequent in asymptomatic patients treated with ritodrine and that these changes may be a physiologic expression of ritodrine-induced tachycardia or hypokalemia. The validity of the use of the presence of electrocardiographic changes as the only criterion for discontinuation of ritodrine therapy is questioned.

Long-term follow-up of children prenatally exposed to ritodrine

In a group of 78 6-year-old children exposed to ritodrine treatment during pregnancy for an average of 28.2 days and in two matched control groups, no statistically significant differences could be found regarding urinalysis, body-length, weight, head circumference, neurological findings, and general behaviour as perceived by parents and teachers. However, school performances of ritodrine-treated children, as estimated by the teacher of the infant school, were considered to be less good. Whether this difference can be attributed to exposure to ritodrine or should rather be explained by the less favourable obstetric situation, which led to imminent preterm delivery, is an unsolved question.

The use of magnesium sulfate for tocolysis in preterm labor complicated by twin gestation and betamimetic-induced pulmonary edema

Maternal cardiorespiratory compromise has been reported to occur during the treatment of preterm labor with tocolytic agents. The risk for these complications is increased by the following factors: multiple gestation, the combination of magnesium sulfate and beta-adrenergic agonist, and the use of adrenocortico-steroids to hasten fetal pulmonary maturity. A case is presented of labor at 28 weeks' gestation complicated by pulmonary edema associated with the three risk factors listed above. The beta-agonist was discontinued with resolution of pulmonary edema. Intravenous magnesium sulfate was continued for 11 days. When uterine contractions finally overcame the tocolysis, delivery occurred. It appeared that uterine quiescence was achieved through the continued use of magnesium sulfate despite pulmonary edema in this case. The risk of continued tocolysis seemed to be counterbalanced by the benefits of prolonged intra-uterine existence for the fetuses.

Maternal ritodrine hydrochloride therapy associated with transient leukemoid reaction in the infant

We have described a preterm infant who had a transient self-limited leukemoid reaction apparently due to maternal ritodrine therapy.

A comparison of ritodrine, terbutaline, and magnesium sulfate for the suppression of preterm labor

Ritodrine, terbutaline, and magnesium sulfate have all been used in the United States as tocolytic drugs. Studies have shown each of these drugs to be effective in suppressing preterm labor. The current study was undertaken in order to compare their relative safety and efficacy and to evaluate the effectiveness of a second drug when the first-used drug failed to stop contractions. No differences in efficacy could be demonstrated between the drugs; however, there was a marked difference in the incidence of maternal side effects. Because of an unacceptable level of side effects, we have stopped the use of terbutaline at our institution.

Complications of beta-mimetic therapy in preterm labour

Selective beta-mimetic drugs are the most frequently used agents for arresting preterm labour. For this purpose these drugs have to be given in high doses for several hours and since they act on several organ systems, side-effects, some of which are potentially dangerous, appear. These hazards, which involve chiefly the cardiovascular and metabolic areas, have been examined in the light of available experience with these drugs. This review considers the possible mechanisms for the side-effects and offers suggestions on how the dangers in the use of beta-mimetic drugs in preterm labour might be avoided.

Atrial myxoma as a complication of tocolytic therapy. A case report

A 27-year-old woman who presented with premature labor was given ritodrine for tocolysis. During the administration of the beta-sympathomimetics she developed cardiac changes, including subendocardial ischemia on EKG and an intermittent early diastolic sound. Echocardiography revealed a large left atrial myxoma. It was removed during pregnancy, and the patient tolerated the procedure well. The mechanism of the ischemia was believed to result from the space-occupying mass of the myxoma, preventing adequate atrial filling and subsequent congestive failure. It is recommended that patients who develop cardiac symptoms during tocolysis with beta-sympathomimetics undergo further investigation to rule out under-lying pathology.

Continuous long-term intravenous beta-sympathomimetic tocolysis

This report concerns the clinical course and outcome of 16 patients treated by continuous long-term intravenous beta-sympathomimetic tocolysis (greater than or equal to 1 week's intravenous therapy). Half of the patients received such therapy for at least 5 weeks. Intravenous tocolysis was adjusted to decrease uterine activity and maintain a satisfactory pulse and blood pressure. Parenteral tocolysis was continued until there was a successful transition to oral therapy, until fetal maturity, or until maternal/fetal indications for delivery were noted. Data indicate that the cardiovascular and metabolic effects were pronounced mostly during the first 3 to 4 days of therapy and then returned toward pretreatment values. In none of the study patients was the treatment discontinued because of drug-related problems, electrocardiogram changes, chorioamnionitis, or fever. The experience indicates that, in a selected group of patients and under close supervision, continuous long-term intravenous beta-sympathomimetic tocolysis may be considered a safe therapeutic modality able to prolong pregnancy with a more desirable outcome.

Metabolic disturbances during intravenous use of ritodrine: increased insulin levels and hypokalemia

The role played by insulin and the adrenergic system in the development of hypokalemia due to intravenous ritodrine has been evaluated. Fifteen women presenting with premature labor (group 1) were treated with ritodrine infusion, whereas seven pregnant women not in labor (group 2) were given 100 g glucose per os to induce hyperinsulinemia without participation of ritodrine. Serum glucose, insulin, potassium, sodium, chloride, and calcium were measured hourly. Whereas insulin levels were higher in group 2, potassium decreased markedly and significantly only in group 1. It is concluded that ritodrine-induced hypokalemia, that results partially from hyperinsulinemia, is mostly determined by other factors and is possibly a consequence of direct beta-adrenoceptor stimulation. Significant hypocalcemia of unexplained origin was observed with ritodrine.

Physiologic and biochemical effects of ritodrine therapy on the mother and perinate

The materno-fetal and neonatal effects of ritodrine were studied in 37 women treated for premature labor with intravenous (i.v.) ritodrine. Marked cardiovascular, respiratory, and biochemical side effects of therapy were seen in the mothers and tachycardia was noted in the fetuses. The neonates of 18 women in whom ritodrine successfully postponed delivery were delivered with good Apgar scores and their admission vital signs and nursery courses were benign. Ritodrine failed to delay delivery more than a week in 19 mothers. There were no differences between their newborns and 20 control neonates in admission vital signs, blood gases, blood chemistries, complete blood counts, platelet counts, peak bilirubin, or duration of oxygen therapy. This study revealed no deleterious effects on neonates delivered after maternal ritodrine therapy despite significant maternal and fetal effects.

Myotonic muscular dystrophy associated with ritodrine tocolysis

A patient thought to be normal was admitted with premature labor at 29+ weeks' gestation. Treatment with the beta-mimetic ritodrine hydrochloride appeared to provoke symptoms of myotonic muscular dystrophy. Neurological history and examination confirmed the presence of previously unsuspected myotonic dystrophy in the patient, her father, and paternal grandfather. Discontinuation of the drug led to improvement in myotonia symptoms but worsening premature labor. Magnesium sulfate did not provoke the same symptoms but was unsuccessful in controlling premature contractions. Long-term management with bed rest, phenytoin, and isoxsuprine hydrochloride resulted in term delivery. Subsequently, maternal symptoms of myotonia disappeared. Congenital myotonia was suspected in the fetus because of the ultrasonic demonstration of polyhydramnios and reduced fetal movements. This was confirmed at delivery. The mechanism by which ritodrine unmasked the myotonia is unclear but may be related to changes in the cell membrane (chloride conductance, the sodium-potassium pump, or membrane polarization).

Cardiovascular consequences of beta-agonist tocolysis: an echocardiographic study

M-mode echocardiography was performed before and during intravenous beta-adrenergic agonist tocolysis in 13 patients with preterm labor. There was a significant increase in heart rate, fractional shortening, and calculated cardiac output. There was also a significant decrease in both end-systolic and end-diastolic left ventricular dimensions, which resolved in 24 to 36 hours. There were, however, no changes in left atrial dimensions. The data derived from this study suggest that the pulmonary edema occasionally complicating beta-adrenergic agonist tocolysis is not the result of systolic cardiac dysfunction.

Respiratory arrest during therapy for premature labor in a patient with myasthenia gravis

A case of premature labor in a woman whose pregnancy was complicated by myasthenia gravis is presented. Ritodrine was given for tocolysis, and betamethasone was administered to accelerate fetal lung maturation. An acute, life-threatening exacerbation of muscular weakness requiring intubation and mechanical ventilation occurred. It appears that betamethasone initiated the respiratory crisis. It is apparent, however, that tocolytic agents currently being used in patients with premature labor (namely, beta-2-sympathomimetics and magnesium sulfate) also have the potential to produce severe exacerbations of weakness, and even respiratory arrest in patients with myasthenia gravis. Each must be used with extreme caution if prescribed for women with this disorder.

Ritodrine-induced pulmonary oedema in labour. Successful management using epidural anaesthesia

A case is described in which unusually high doses of intravenous ritodrine were used for 6 weeks to postpone premature labour. Treatment was complicated by tachydysrhythmias and pulmonary oedema. Epidural analgesia was used successfully for pain relief during labour and Caesarean section. The pathophysiology is discussed.

Evaluation of seven- to nine-year-old children exposed to ritodrine in utero

Twenty children who had been exposed to ritodrine in the management of preterm labor between 24 and 34 weeks' gestational age were examined at seven to nine years of life and compared with matched control subjects. No significant differences were detected in factors of growth, neurologic findings, and psychometric testing.

Addition of magnesium sulfate improves effectiveness of ritodrine in preventing premature delivery

From October, 1981, to July, 1983, 225 patients were evaluated for premature labor at Forsyth Memorial Hospital. Sixty-five of these patients were considered to be candidates for intravenous ritodrine treatment. Of this group, 24 patients were successfully treated and had pregnancy prolongation ranging from 1 to 17 weeks. Forty-one patients did not respond to maximal intravenous ritodrine therapy (300 to 350 micrograms/min). Eleven patients subsequently delivered within 24 to 48 hours of treatment initiation. The remaining 30 patients received intravenous magnesium sulfate (1 to 3 gm/hr) in addition to intravenous ritodrine. Eighteen patients responded favorably to this combination treatment and had pregnancy prolongation ranging from 1 to 11 weeks. Twelve patients delivered within 1 week from treatment initiation. In all cases where pregnancy prolongation was achieved, birth weight and neonatal outcome were significantly improved compared to patients who did not respond to either intravenous ritodrine alone or intravenous ritodrine and magnesium sulfate combination. Treatment related maternal/fetal complications were not significantly different in the various groups examined. From the foregoing we conclude that, in a select group of patients in premature labor not responding to conventional ritodrine therapy, magnesium supplementation in pharmacologic doses could have a beneficial effect with respect to pregnancy outcome.

Aminophylline treatment of preterm labor

Prevention of neonatal mortality linked to prematurity may be achieved by treating preterm labor, thus allowing fetal lungs to spontaneously develop, or by administering drugs able to enhance pulmonary maturation. The methylxantine derivative aminophylline has been reported to reduce uterine contractility and increase the concentrations of saturated phosphatidylcholine in fetal lungs. Its effectiveness in treating preterm labor and preventing respiratory distress syndrome (RDS) has been evaluated in comparison to the widely used drug ritodrine. In 39 pregnant women with preterm labor the efficacy of aminophylline and ritodrine in delaying the delivery seemed similar. However, while two of the babies born from ritodrine treated mothers died because of RDS, all babies born from aminophylline-treated mothers survived. These data might then confirm the effectiveness of aminophylline treatment to prevent RDS.

A double-blind study comparing ritodrine and terbutaline in the treatment of preterm labor

One hundred women in preterm labor were randomly treated with ritodrine or terbutaline in a double-blind fashion. The drugs were comparably effective during intravenous therapy but, in women with intact membranes, an oral dose of terbutaline, 30 mg daily, was significantly more effective than ritodrine, 120 mg daily, in preventing recurrent labor during a 5-day course of oral therapy (one of 19 versus 12 of 23, p less than 0.001). In women with intact membranes, pregnancy was prolonged 40 +/- 25 days (mean +/- SD) in women receiving terbutaline orally and only 22 +/- 24 days in women receiving ritodrine orally (p less than 0.01). In women with intact membranes, a heart rate greater than or equal to 130 bpm occurred in in a higher proportion of women receiving intravenous treatment with ritodrine than among those receiving terbutaline (20 of 31 versus 8 of 27, p less than 0.05). Terbutaline-treated women, however, were significantly more likely to have a serum glucose level in excess of 140 mg/dl than were women treated with ritodrine (13 of 26 versus 6 of 29, p less than 0.05). Side effects commonly observed during intravenous therapy included nausea (22%), chest pain (15%), and shortness of breath (15%). Side effects were significantly (p less than 0.025) more likely to occur during periods when the infusion rate was being increased rather than during periods when the infusion rate was constant.

Potassium supplementation in ritodrine-induced hypokalemia

Acute hypokalemia occurs during infusion of beta 2 agonists for tocolysis. This study examines the efficacy of supplemental potassium in treating this hypokalemia. Four groups of dogs were anesthetized and given lactated Ringer's solution (group I), potassium chloride (group II), ritodrine hydrochloride (group III), and ritodrine plus potassium (group IV). Arterial blood gases, pH, and serum and urinary electrolytes were measured. Results were analyzed by an analysis of variance. Serum potassium fell in groups I and III, rose in group II, and remained stable in group IV. Urinary potassium levels in groups that received ritodrine (III and IV) were not different from control levels. Potassium given with ritodrine will prevent hypokalemia. However, the risks of hyperkalemia exist if vigorous replacement is undertaken. There were no dysrhythmias and no adverse effects in any of the hypokalemic animals. Therefore, the routine administration of potassium is not advocated even in obstetric patients who undergo general anesthesia.

Pulmonary edema during cesarean section related to the use of oxytocic drugs

We report the case of an acute pulmonary edema occurring during cesarean section under general anesthesia in a previously healthy negro parturient. This acute event was probably due to the hemodynamic effects of three oxytocic drugs, oxytocin, methylergometrine maleate and prostaglandin F2 alpha used to control severe third-stage bleeding in interaction with the hemodynamic effects of pregnancy at term and surgical and anesthetic stress. The cardiovascular effects of these drugs are reviewed. For a safer conduct of anesthesia, oxytocin for control of uterine bleeding is recommended to be administered by slow intravenous drip and ergometrin by intramuscular injection. The safety of the intramyometrial injection of PGF2 a still remains to be proven.

Prevention of preterm delivery. The important role of early recognition

Perinatal deaths can be decreased most effectively by reducing the incidence of preterm delivery. Therapy with a tocolytic agent, such as ritodrine ( Yutopar ), can be of significant benefit if applied to patients in whom preterm labor is correctly diagnosed and has not advanced beyond the early stages. Identification of the patient at risk, intensive education and surveillance of such patients, and education of hospital and clinic staff can extend the application and success of labor-inhibiting therapy.

Adjunctive use of magnesium sulfate with ritodrine for preterm labor tocolysis

The purpose of the study was to determine if the adjunctive administration of magnesium sulfate with ritodrine would result in decreased dosage requirements of ritodrine, and, therefore, decrease the incidence of ritodrine-associated side effects. Candidates for tocolysis were prospectively randomized so that some received a uniform tocolytic dose of magnesium sulfate in a blinded protocol. All patients received a ritodrine infusion which was titrated in the standard manner to achieve cessation of labor. Evaluations included interval cumulative ritodrine dose, maximal ritodrine infusion rate, fluid balance, and blood chemistry studies. Contrary to our hypothesis, there were significantly more cardiovascular effects in the group that received ritodrine plus magnesium sulfate (11/24) than in the group that received ritodrine alone (1/17) (p less than or equal to 0.02). The predominant side effect was chest pain, frequently associated with electrocardiogram changes indicative of myocardial ischemia. These results are consistent with the current understanding of the regulatory mechanisms of these tocolytic agents. We conclude from the results of our prospective, randomized, blinded study that the adjunctive use of magnesium sulfate with ritodrine is associated with an unacceptable increase in serious side effects and probably does not improve efficacy.

Breast engorgement and galactorrhea after preventing premature contractions with ritodrine

Breast engorgement and galactorrhea were observed in many patients receiving ritodrine treatment to delay labor due to premature contractions. In an attempt to understand the causes for these phenomena, serum prolactin, progesterone, estradiol and estriol excretion were measured in 11 women. No statistical difference was found in these parameters after ritodrine administration. It can thus be assumed that breast engorgement and galactorrhea after ritodrine treatment are unrelated to changes in these hormones but might be mediated by some other factors or probably by the premature contractions themselves.

Effects of maternal ritodrine administration on neonatal renal function

Because of its effects on the cardiovascular and renin-angiotensin systems and on fluid and electrolyte homeostasis, maternal administration of ritodrine to inhibit preterm labor may cause significant alterations in renal function in the newborn infant. We determined inulin clearance, plasma renin activity, urinary arginine vasopressin excretion, and serum and urine electrolyte concentrations and osmolalities at 12 to 36 hours of life and at 6 days of life in 15 infants whose mothers had received ritodrine and in 15 infants whose mothers did not (control infants). At the time of each study, plasma ritodrine concentrations were obtained in the infants whose mothers received ritodrine. The infants whose mothers had received ritodrine had significantly lower inulin clearances and higher plasma renin activity and urinary arginine vasopressin excretion on day 1 but not on day 6. Gestational age was inversely correlated with plasma ritodrine concentration, plasma renin activity, and urinary arginine vasopressin excretion. There were no overt clinical signs of renal failure in any of the infants, and no differences in serum and urine electrolyte values, osmolality, fractional sodium excretion, or urine flow rate were observed between the groups.

Pulmonary edema induced by betamimetic drugs

We present six cases of pulmonary edema related to betamimetic (beta sympathomimetic amine) agents (three to ritodrine and three to terbutaline). The hemodynamic data from three patients suggest that this may be a form of noncardiogenic pulmonary edema. A seventh case, resulting in a maternal death, is included because of the association with ritodrine therapy and the instructive complications of invasive monitoring. We also propose an outline for the management of betamimetic-drug-induced pulmonary edema.

Ritodrine in the treatment of preterm labour: a study of 213 patients

In a study of 213 patients with diagnosed, uncomplicated preterm labour up to 33 weeks gestation, intravenous followed by oral ritodrine (Yutopar) was found to be an effective treatment. Success rate was related to Bishop score at commencement of therapy, the mean time to delivery being 36.9 days. It was greater than or equal to 56 days in 26.5% of patients and greater than or equal to 2 days in 91%. Relapse rate was low if infusion was followed by an adequate oral dosage. Concurrent signs and symptoms were seen in a third of patients but drug withdrawal was only necessary in seven. There was no significant difference in the incidence of respiratory distress syndrome between the infants of patients treated with ritodrine alone and those of patients treated with ritodrine plus steroids.

Neonatal outcome after treatment with ritodrine: a controlled study

Neonatal condition was assessed in a group of 82 infants born at term after maternal treatment with ritodrine for an average of 28.5 days, and compared with that in a matched control group of infants. No statistically significant differences were found in umbilical pH, Apgar scores, head circumference, and neurological condition. Although the difference was not statistically significant, doubt remains as to a possible icterogenic effect of ritodrine.

Ritodrine hydrochloride infusion in pregnant baboons. I. Biophysical effects

Pulmonary edema is a potentially fatal complication of beta-sympathomimetic therapy for premature labor. Isolated case reports have supported either primary pulmonary capillary membrane injury or left ventricular failure as the cause of pulmonary edema. By simultaneously monitoring cardiac function and extravascular lung water in six control and six ritodrine hydrochloride-treated pregnant baboons, we attempted to define this pathophysiology. The pulmonary capillary wedge pressure increased in treated animals, reaching significance at 16 hours of ritodrine treatment (p less than 0.0001) concurrent with the maximum increase in cardiac index (p = 0.02). Treated animals also retained 61% of intravenously administered fluids compared with 23% in untreated control animals (p less than 0.002). There were, however, no significant differences between groups in extravascular lung water, central venous pressure, or pulmonary artery pressure. Chest radiographs and arterial blood gas analysis were also comparable between ritodrine-treated and control animals. Fluid retention and elevated hydrostatic pressure are postulated as the etiology of beta-sympathomimetic-induced pulmonary edema. There was no evidence to support a primary pulmonary capillary membrane injury by ritodrine.