***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    ***EXAMPLES*** 
    Input: 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 . C and i date s for tocolysis were prospect ively r and omized 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 st and ard 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 underst and ing of the regulatory mechanisms of these tocolytic agents . We conclude from the results of our prospect i ve , r and omized , 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 BACKGROUND The efficacy and safety of repeat doses of prenatal corticosteroids remains uncertain . Our aim was to establish whether repeat prenatal corticosteroids given to women at risk of preterm birth can reduce neonatal morbidity without harm . METHODS In this hospital-based study , 982 women who remained at risk of preterm birth at less than 32 weeks ' gestation , 7 or more days after receiving a first course of prenatal corticosteroids  , were r and omly assigned to receive a repeat intramuscular dose of either 11.4 mg betamethasone ( as Celestone Chronodose ) , or saline placebo . This was repeated every week the woman remained undelivered , at less than 32 weeks ' gestation , and at risk of preterm birth . Primary outcomes were occurrence and severity of neonatal respiratory distress syndrome , use and duration of oxygen and mechanical ventilation , and weight , length , and head circumference at birth and hospital discharge . Statistical analyses were on an intention to treat basis . This study is registered as an International St and ard R and omised Controlled Trial , number IS RCT N48656428 . FINDINGS Fewer babies exposed to repeat corticosteroids had respiratory distress syndrome ( 33%vs 41 % ; relative risk 0.82 , 95 % CI 0.71 - 0.95 , p=0.01 ) and fewer had severe lung disease ( 12%vs 20 % ; relative risk 0.60 , 95 % CI 0.46 - 0.79 , p=0.0003 ) than those in the placebo group . In keeping with these benefits , babies exposed to repeat corticosteroids needed less oxygen therapy ( p=0.03 ) , and shorter duration of mechanical ventilation ( p=0.01 ) . Mean weight , length , and head circumference at birth and hospital discharge did not differ between treatment groups . Z-scores for weight ( p=0.04 ) and head circumference ( p=0.03 ) at birth were lower in the babies who received repeat corticosteroids although at the time of hospital discharge Z-scores did not differ between treatment groups ( p=0.29 for weight , p=0.48 for head circumference ) . INTERPRETATION Exposure to repeat doses of antenatal corticosteroids reduces neonatal morbidity . Pending long-term outcome results , the short-term benefits for the babies in our study support the use of repeat doses of corticosteroids in women who remain at risk of very preterm birth 7 or more days after an initial course The purpose of this study was to describe the course of  preterm labor in patients receiving a st and ard intravenous infusion of the oxytocin antagonist atosiban .  An open-labeled , non-r and omized study was conducted at 4 sites . Successful tocolysis was defined as delay of delivery larger than 48 hours from starting atosiban and no need for an alternate tocolytic . Atosiban was administered by continuous intravenous infusion at a rate of 300 micrograms per minute until uterine contractions were absent for 6 hours , or up to a maximum infusion time of 12 hours . Sixty-two patients of between 20 and 36 weeks ' gestation were enrolled over 6 months . One had rupture of membranes and was excluded .  Successful tocolysis was noted in 43 of 61 ( 70.5 % ) . Four delivered spontaneously within 48 hours and 14 ( 23.0 % ) required an alternate tocolytic agent . The chance of successful tocolysis was related to the degree of cervical dilation at the start of therapy . Cessation of uterine contractions was noted in 38 patients ( 62.3 % ) . A decrease in uterine contraction frequency of 50 % or more was noted in 50 of 61 patients ( 82.0 % ) . Four patients reported side effects ( nausea , vomiting , headache , dysguesia , chest pain ) , but in no case did side effects require discontinuation of the medication . Intravenous administration of atosiban is associated with a delay in delivery comparable to that seen with other tocolytics . If this effect is confirmed in planned placebo-controlled trials , its favorable side effect profile may give it a place in the armamentarium The purpose of this r and omized study was to compare the efficacy of ritodrine alone ( 51 ) versus ritodrine plus magnesium gluconate ( 56 ) . We concluded that high oral doses of magnesium therapy ( 4 x 3 gr ) potentiate the effects of intravenous beta-agonists , allowing a reduction of the dosage needed and a better " tolerance " . Considering the low side effects , it seems reasonable to consider using magnesium in the treatment of premature labour Objectives . We evaluated the efficacy of magnesium sulfate as a second-line tocolysis for 48 hours . Material s and Methods . A multi-institutional , simple 2-arm r and omized controlled trial was performed . Forty-five women at 22 to 34 weeks of gestation were eligible , whose ritodrine did not sufficiently inhibit uterine contractions . After excluding 12 women , 33 were r and omly assigned to either magnesium alone or combination ( ritodrine and magnesium ) . The treatment was determined as effective if the frequency of uterine contraction was reduced by 30 % at 48 hours of the treatment . Results . After magnesium sulfate infusion , 90 % prolonged their pregnancy for > 48 hours . Combination therapy was effective in 95 % ( 18/19 ) , which was significantly higher than 50 % ( 7/14 ) for magnesium alone . Conclusion . This r and omized trial revealed that combination therapy significantly reduced uterine contractions , suggesting that adjuvant magnesium with ritodrine is recommended , rather than changing into magnesium alone , when uterine contractions are intractable with ritodrine infusion Objective . Red blood cell ( RBC ) deformability is an important factor in determining movement of red blood cells through the microcirculation . In preeclampsia and some cases of intrauterine growth restriction ( IUGR ) , RBC deformability and microcirculation are reduced . Magnesium is administered to reduce the risk of seizures . The aim of this study was first to detect the effect of intravenous magnesium application ( 2 g/h ) on the deformability of RBCs in pregnancies with normal RBC deformability , receiving magnesium as tocolytic agent . The second aim was to examine the effect of calcium-antagonists ( magnesium , nifedipin ) on the deformability of RBC of preeclamptic patients in vitro . Methods . Part 1 : magnesium ( 2 g/h ) , fenoterol ( 270 µg/h ) + verapamil ( 0.2 mg/h ) or placebo ( NaCl 0.9 % ) was administered intravenously to pregnant women with premature contractions to test the tocolytic effect . RBC-deformability was measured by laser diffractoscopy in all three groups . Blood sample s were taken before , after 1 h and after 24 h of administration . Magnesium-plasma-levels were measured . Part 2 : Blood sample s from patients with preeclampsia were incubated in vitro with magnesium ( 2 mmol ) , nifedipine ( 0.25 mg/ml ) , or placebo ( NaCl 0.9 % ) . RBC deformability was measured before and 15 min , 1h , 2h , 6h , and 10h after start of the incubation . Results . Part 1 : The initial RBC-deformability was the same in all groups ( E=0.232 ± 0.017 in NaCl , 0.232 ± 0.023 in fenoterol + verapamil , 0.232 ± 0.019 in magnesium ) . After 1 h of administration , RBC-deformability was significantly greater with magnesium ( 0.254 ± 0.020 ) and Fenoterol + Verapamil ( 0.238 ± 0.02 ) compared to placebo ( 0.231 ± 0.015 ) . After 24 h the effect on RBC deformability in the fenoterol + verapamil-group was gone ( 0.234 ± 0.021 compared to 0.234 ± 0.016 in placebo ) , while in the IV-magnesium-group  RBC-deformability remained increased ( E=0.241 ± 0.019 ) . Statistical analysis of the influence of magnesium-plasma-levels showed the maximum effect at concentrations of 1.95–2.15mmol/l . Part 2 : RBC-deformability in preeclampsia was reduced as predicted by previous studies ( 0.120 + 0.0086 versus 0.232 in normal pregnancy ) . In vitro incubation with magnesium  enhanced RBC-deformability in preeclampsia . Even after 15 min , a statistically significant effect was seen ( 0.127 ± 0.0091 versus 0.121 ± 0.0091 in placebo ) . Maximum effect was reached after 6 h of incubation ( 0.159 ± 0.0093 versus 0.133 ± 0.0091 ) . Incubation with Nifedipine  also enhanced RBC deformability [ 0.127 ± 0.0091 after 15 min , 0.149 ± 0.010 after 6 h ( maximum effect ) ] , but the effect was less pronounced than with magnesium . Conclusion . Intravenous magnesium therapy over a 24-hour period increases RBC-deformability even in pregnancies with normal RBC-deformability . In vitro measurements show an increase of RBC-deformability in preeclampsia in response to magnesium , which could offer additional therapeutic benefit for the treatment of reduced blood flow seen in most cases of preeclampsia Seventeen patients in advanced premature labor ( cervical dilatation greater than or equal to 3 cm and effacement greater than or equal to 50 % ) were r and omized in a double-blind protocol to receive metoprolol ( a beta 1-adrenergic antagonist ) or a placebo in conjunction with intravenous and oral terbutaline ( a beta 2-agonist ) in an attempt to inhibit the side effects of terbutaline . Both groups of patients had a dose-related increase in heart rate and systolic blood pressure and a decrease in diastolic blood pressure . Laboratory studies revealed significant hyperglycemia , hypokalemia , hypocalcemia , and acidosis during the intravenous terbutaline infusion , all of which normalized during oral terbutaline therapy . There were no significant differences in the cardiovascular or metabolic responses to terbutaline between the metroprolol and placebo patients . The mean delay in delivery was 5.7 days , with 59 % of patients having delivery delayed for 48 hours or more . The mean prolongation time was shorter , but not statistically significant , for those patients receiving metroprolol . Despite the use of high-dose terbutaline , there were no significant complications of therapy . There was little efficacy of infusion dosages above 40 micrograms/min or repeated courses of intravenous tocolysis . Although recent reports do not recommend tocolysis in these patients , this study suggests that combined beta-mimetics and glucocorticoids may be the optimal care for patients in advanced premature labor , in particular , those with infants of very low birth weight A prospect i ve and double-blind study was undertaken to compare the effectiveness of two different treatments on two r and omized groups of patients with threatened preterm labor . The first treatment consisted of the administration of ritodrine and a placebo ; in the second , ritodrine was combined with indomethacin .  22 patients were evaluated in each group . The results obtained for gain in days , number of patients delivered at term , weight of newborns and number of recurrences in each group suggest that treatment with ritodrine and indomethacin  is slightly but significantly more effective than treatment with ritodrine and placebo in prolonging pregnancy . No evidence has been found of possible unfavorable vascular effects of indomethacin in the fetus 
    Output:
    
There were no significant differences between groups receiving IV ritodrine plus vaginal progesterone compared with IV ritodrine alone for most outcomes reported , although the latency period ( time from recruitment to delivery ) was increased in the group receiving the combination of tocolytics .
For other combinations of tocolytic agents , primary outcomes were rarely reported and for secondary outcomes results did not demonstrate differences between groups .