Administration Of Atosiban Research Articles

O-029 Atosiban in women with previous single implantation failure undergoing frozen-thawed blastocyst transfer: a placebo-controlled randomized trial

Abstract Study question Does the administration of Atosiban before frozen-thawed blastocyst transfer improve the live birth rate in women with a history of a single implantation failure? Summary answer In women with a single implantation failure undergoing frozen-thawed blastocyst transfer, Atosiban did not improve the ongoing pregnancy rate. What is known already Uterine peristalsis preceding embryo transfer is believed to adversely impact the success rates of IVF. Atosiban can reduce uterine peristalsis and act as a role of oxytocin antagonist. The effectiveness of Atosiban in the general population of IVF patients has not been conclusively shown by randomised clinical trials or meta-analyses. It has been suggested that women with previous implantation failure may potentially benefit from the use of Atosiban, particularly in the presence of uterine peristalsis. We aim to evaluate if Atosiban before embryo transfer increases live birth rate in women undergoing frozen-thawed blastocyst transfer? Study design, size, duration We conducted a single-centre, double-blind placebo randomised controlled trial (RCT) in women with previous single implantation failure undergoing frozen-thawed blastocyst transfer. Between July 2019 and June 2023, we randomised 1,100 participants to either Atosiban or placebo. The primary outcome was live birth (≥20 weeks of gestation) in the first FET after randomization. In this abstract, we present results on ongoing pregnancy. Data on live birth will be available at the conference. Participants/materials, setting, methods We randomised women with a history of one failed fresh or frozen blastocyst, with at least one cryopreserved blastocyst into two groups on the day of transfer. In the Atosiban group, women were administered 37.5mg of Atosiban intravenously 30-min prior to FET. In the placebo group, women received a saline infusion for the same duration. Uterine peristalsis was measured using transvaginal ultrasound prior to administration of study drugs. The analysis was done based on intention-to-treat. Main results and the role of chance The ongoing pregnancy rates were 50.46% (277/549) and 46.82% (258/551) in the Atosiban and control groups, respectively (RR 1.08, 95% CI 0.95 to 1.22, P = .23). Uterine peristalsis was measured in 720 (65%) of all participants. Within this cohort, of the 163 (22%) women with abnormal contractions, the ongoing pregnancy rates were 51.9% and 41.7%, respectively (RR 1.25, 95% CI 0.90 to 1.73, P = .19). Among 208 women (29%) with peristalsis but without abnormal contraction waves, ongoing pregnancy rates were 50.9% and 48.0% (RR 1.06, 95% CI 0.81 to 1.40, P = .67). In 349 women (48%) without peristalsis, the ongoing pregnancy rates were 48.6% in the Atosiban group versus 50.6% in the control group (RR 0.96, 95% CI 0.78 to 1.19, P = .71). Limitations, reasons for caution Our study only included women with previous blastocyst implantation failure. Uterine peristalsis was not initially assessed, resulting in only 65% (720/1,100) of the participants having peristalsis measured. In this abstract, we only report on the ongoing pregnancy rate. We will present data on live birth at the congress. Wider implications of the findings In unselected women undergoing frozen-thawed blastocyst transfer with previous single implantation failure, Atosiban does not enhance the ongoing pregnancy rate. Future research regarding Atosiban in IVF should assess uterine peristalsis and focus on women with abnormal contractions. Trial registration number ChiCTR1900022333

Administration of Atosiban, an oxytocin receptor antagonist, ameliorates autistic-like behaviors in a female rat model of valproic acid-induced autism

Autism spectrum disorder (ASD) is a pervasive developmental disorder with gender differences. Oxytocin (OXT) is currently an important candidate drug for autism, but the lack of data on female autism is a big issue. It has been reported that the effect of OXT is likely to be different between male and female ASD patients. In the study, we specifically explored the role of the OXT signaling pathway in a VPA-induced female rat’s model of autism. The data showed that there was an increase of either oxytocin or its receptor expressions in both the hippocampus and the prefrontal cortex of VPA-induced female offspring. To determine if the excess of OXT signaling contributed to autism symptoms in female rats, exogenous oxytocin and oxytocin receptor antagonists Atosiban were used in the experiment. It was found that exogenous oxytocin triggered autism-like behaviors in wild-type female rats by intranasal administration. More interestingly, several autism-like deficits including social interaction, anxiety, and repeat stereotypical sexual behavior in the VPA female offspring were significantly attenuated by oxytocin receptor antagonists Atosiban. Moreover, Atosiban also effectively improved the synaptic plasticity impairment induced by VPA in female offspring. Our results suggest that oxytocin receptor antagonists significantly improve autistic-like behaviors in a female rat model of valproic acid-induced autism.

Atosiban-induced acute pulmonary edema: A rare but severe complication of tocolysis

BackgroundAtosiban is commonly used to delay premature labor in pregnant women and is thought to have few side effects. ObjectivesTo report a case of acute pulmonary edema (APE) following administration of atosiban and conduct a systematic review to identify common characteristics and risk factors of atosiban-associated APE. MethodsSearches were performed in Pubmed, Embase, and Web of Science using the keyword “Atosiban” combined with the terms “Pulmonary edema” or “Dyspnea” or “Hypoxia” on 9th July 2022. Only case reports of atosiban-associated APE were included without language restrictions. Data were extracted from the reports, and median, range, and percentages were calculated as applicable. The risk of bias was assessed using the Joanna Briggs Institute critical appraisal checklist for case reports. ResultsSeven cases of atosiban-associated APE were included in the systematic review, including our case. APE occurred at a median gestational age of 32 + 6 weeks. Most patients were nulliparous (6/7, 85.7%) and were in multiple pregnancies (5/7, 71.4%). All patients were prescribed antenatal corticosteroids and tocolytics, with three (42.9%) receiving only atosiban and four (57.1%) receiving atosiban and other tocolytics. The median interval from starting atosiban administration to APE onset was about 40 h, and three patients (42.9%) showed symptoms 2–10 h after the end of atosiban treatment. Radiographic examinations (chest X-ray and/or computer tomography scan) confirmed APE in all patients and pleural effusion in four patients (57.1%). Five patients (71.4%) underwent emergency cesarean section, one patient (14.3%) with twin pregnancy had vaginal delivery with the help of suction cup and forceps, and another patient (14.3%) continued the pregnancy. All patients recovered well after administration of oxygen, diuresis, and other supportive therapy. ConclusionAtosiban may cause acute pulmonary edema in patients with underlying risk factors. This complication remains rare, but caution during tocolytic treatment using atosiban is recommended.

A randomized double blind comparison of atosiban in patients with recurrent implantation failure undergoing IVF treatment

BackgroundPatients with recurrent implantation failure (RIF) may have more uterine contractions. Several observational studies suggested that atosiban administration around embryo transfer resulted in higher pregnancy rates in RIF patients. This study aimed to evaluate the effect of atosiban given before fresh embryo transfer on pregnancy outcomes of women with RIF.MethodsA prospective, randomized, double-blind controlled clinical trial was performed in IVF center of Shanghai First Maternity and Infant Hospital. According to a computer-generated randomization list, 194 infertile women with RIF received fresh embryo transfer between July 2017 and December 2019 were randomly allocated into the atosiban (n = 97) and the placebo (n = 97) groups. Women in the treatment group received atosiban intravenously about 30 min before embryo transfer with a bolus dose of 6.75 mg over one minute. Those in the placebo group received only normal saline infusion for the same duration.ResultsThere was no significant difference in the live birth rate between the atosiban and placebo groups (42.3% vs 35.1%, P = 0.302, RR = 1.206 (0.844–1.723)). No significant differences were found between the two groups in the positive pregnancy test, clinical pregnancy, ongoing pregnancy, miscarriage, multiple pregnancy, ectopic pregnancy and implantation rates. Similar results were found when stratified by the number of embryos previously transferred, number of previous failed embryo transfers, frequency of endometrial peristalsis on embryo transfer day (≥ 3 waves/min) or serum estradiol (E2) on the day of hCG above the median level. And, there was no correlation between the serum E2 level on the day of hCG and the frequency of endometrial peristalsis on embryo transfer day. The frequency of endometrial peristalsis on embryo transfer day, total FSH/HMG dosage and duration were the significant factors which independently predicted the likelihood of a live birth.ConclusionsThese results suggested that atosiban treatment before fresh embryo transfer might not improve the live birth rate in RIF patients.Trial registrationThe study had been approved by the Institutional Review Board of the hospital (2017 ethics No.43) and was registered under Clinicaltrials.gov with an identifier NCT02893722.

Uterotonic Effects of Aqueous and Methanolic Extracts of Lannea acida in Wistar Rats: An In Vitro Study.

Lannea acida (Anacardiaceae), commonly called Kikié in the Noun division (West-Cameroon), is a tree whose bark is used locally to facilitate delivery. This study was aimed at evaluating the in vitro uterotonic effects of aqueous and methanol extracts of L. acida in Wistar rats. Uterine strips isolated from rats pretreated with 5μg estradiol (48h) were mounted in a single-organ bath containing aerated and thermostated De Jalon solution (37°C). After equilibration, non-cumulative effects of L. acida extracts were recorded after application. The effect of the methanol extract (the most active extract) was monitored in the presence of atosiban (a competitive antagonist of oxytocin receptors), atropine (a specific type 3 muscarinic receptor antagonist), nifedipine (an L-type calcium channel antagonist), and 2-Aminoethoxydiphenyl borate (2-ADB, a specific antagonist of inositol 1,4,5-triphosphate receptors type 1), and in calcium-free medium containing EGTA to elucidate its mechanism of action. L. acida induced uterine contraction in a concentration-dependent manner with the methanol extract (1.506 ± 0.032 gf) being the most effective. Administration of atosiban (2μmol/L) and atropine (1μmol/L) reduced the contractile effect of L. acida. Complete inhibition was observed with nifedipine, 2-APB, and calcium-free medium containing EGTA. These results suggest that L. acida possesses uterotonic effects mediated through oxytocin receptors with mobilization of extracellular calcium.

Pregnancy and neonatal outcomes of hyperglycemia caused by atosiban administration during pregnancy

Pregnancy and neonatal outcomes of hyperglycemia caused by atosiban administration during pregnancy

The Effect of Atosiban on Patients With Difficult Embryo Transfers Undergoing In Vitro Fertilization-Embryo Transfer.

The purpose of this study was to evaluate the effect of atosiban on the outcomes of infertile women undergoing in vitro fertilization (IVF) with difficult embryo transfers (ETs). This randomized double-blind study enrolled 204 infertile women with difficult ETs during IVF treatment between June 2014 and June 2018. According to a computer-generated randomization list, participants were randomized into placebo (n = 102) and atosiban (n = 102) groups. In atosiban group, atosiban with a total dose of 37.5 mg was administered. All of the patients underwent IVF-ET using cryopreserved embryos. The clinical pregnancy rate per cycle and implantation rate per transfer (45.1% and 26.5%) in atosiban group were significantly higher than those of placebo group (15.6% and 9.7%, respectively; P < .05). This study showed that administration of atosiban during ET was extraordinarily effective for patients with difficult transfers.

Oxytocin effects on the inhibition of the NF-κB/miR195 pathway in mice breast cancer

Oxytocin (OT) has the suppressive effects on breast tumor formation and development. We hypothesized that OT through the NF-κB inhibition can induce the miR-195 up-regulation which it can promote the cell apoptosis and inhibit the cell proliferation. Thirty-two BALB/c female mice were equally divided into four groups to study the effects of OT and atosiban (ATO) (an oxytocin receptor antagonist) on the mammary tumor growth. The animal weight, OT plasma concentration, and the tumor weight and volume were measured. Moreover, the tumor-related signaling pathways including NF-κB, miR-195, and Cyclin D1 were evaluated by qPCR assays, and Akt and ERK proteins were assessed by western blot at the end of the study. The volume and weight of tumors were significantly decreased after OT administration. The phosphorylated Akt and ERK expressions were significantly decreased in the OT group compared to the tumor group. In contrast, the dephosphorylated Akt and ERK expressions were significantly increased in the OT group in comparison with the tumor group. The mRNA expressions of miR-195, OTR, and Bax genes were significantly increased, and the mRNA expression of ERα, PI3K, NF-κB, cyclin D1 and Bcl-2 genes were decreased in the OT group in comparison with the tumor group. Interestingly, ATO administration reversed these effects. These results can exhibit a new therapeutic potential for OT on the down-regulation of the NF-κB and up-regulation of miR-195 and consequently, decrease of the tumor volume and weight in a mouse model of breast cancer.

Perception of social interaction compresses subjective duration in an oxytocin-dependent manner.

Communication through body gestures permeates our daily life. Efficient perception of the message therein reflects one's social cognitive competency. Here we report that such competency is manifested temporally as shortened subjective duration of social interactions: motion sequences showing agents acting communicatively are perceived to be significantly shorter in duration as compared with those acting noncommunicatively. The strength of this effect is negatively correlated with one's autistic-like tendency. Critically, intranasal oxytocin administration restores the temporal compression effect in socially less proficient individuals, whereas the administration of atosiban, a competitive antagonist of oxytocin, diminishes the effect in socially proficient individuals. These findings indicate that perceived time, rather than being a faithful representation of physical time, is highly idiosyncratic and ingrained with one's personality trait. Moreover, they suggest that oxytocin is involved in mediating time perception of social interaction, further supporting the role of oxytocin in human social cognition.

Oxytocin Receptor Antagonist (Atosiban) in the Threat of Preterm Birth: Does It Have Any Effect on Breastfeeding in the Term Newborn?

Oxytocin is a hormone involved in the mechanism of breastfeeding, uterine contractions, and social relationships. Atosiban (competitive oxytocin antagonist) is one of the most commonly used tocolytics for the threat of preterm labor in Europe. The aim of this study is to determinate if the administration of atosiban has any influence in the type of feeding in the term newborn at discharge. The secondary objective is to verify its effectiveness for the prevention of preterm delivery and in the possibility of applying treatment to complete lung maturation. Retrospective cohort study carried out in a tertiary University Hospital distinguished by WHO-UNICEF as a Baby-Friendly Hospital Initiative. The analysis included 264 women exposed to atosiban during a period of 4 years. One hundred met inclusion criteria. Unexposed infants born right after and before the exposed ones were selected as the not exposed subgroup (n = 200). Among women treated with atosiban, 82% maintained exclusively breastfed (EBF), 8% had mixed breastfeeding, and 10% had formula feeding at discharge. In the nonexposed group, 82% maintained EBF, 9.5% had mixed breastfeeding, and 8.5% had formula feeding at discharge (p = 0.84). 97.5% of pregnant women treated with atosiban received corticosteroid for lung maturation, and 49.5% completed gestation with term newborns. There were no significant differences in the type of feeding at discharge between the atosiban group and the nonexposed group. In most cases, the administration of tocolytic therapy allowed to complete lung maturation.

Administration of atosiban in patients with endometriosis undergoing frozen–thawed embryo transfer: a prospective, randomized study

To examine the effects of atosiban, given before transfer of frozen-thawed embryo to women with endometriosis (EMs). A randomized, controlled clinical trial. University hospital and IVF center. One hundred twenty women with endometriosis undergoing frozen-thawed embryo transfer were randomly allocated into the atosiban treatment and the control groups. Another 120 women with infertility due to tubal factor were enrolled into a tubal factor group, to compare serum oxytocin (OT) and prostaglandin (PG)F2α levels and uterine contractions with the endometriosis group. In the endometriosis treatment group, a single bolus (6.75mg, 0.9mL per vial) of atosiban was administrated before ET. Implantation rate and pregnancy rate. Serum OT level (1.89 ± 0.33 vs. 1.66 ± 0.32ng/L), PGF2α (2.83 ± 0.34 vs. 2.36 ± 0.35ng/L) level, and uterine contractions (2.5 ± 1.2 vs. 1.8 ± 1.0 waves per minute) in the endometriosis group were all significantly higher than in the tubal factor group. The clinical pregnancy rate per cycle and implantation rate per transfer were 58.3% and 41.0%, respectively, in the atosiban treatment group, significantly higher than in the control group (38.3% and 23.4%, respectively). Women with endometriosis showed higher serum OT level, PGF2α level, and uterine contractions. Atosiban treatment before ET in endometriosis is effective in the priming of the uterus, suitable for embryo implantation. This is the first study to evaluate the effect of atosiban treatment in patients with endometriosis. ChiCTR-IOQ-14005715.

P14.05: Preliminary report of 48‐hours Atosiban administration in spontaneous preterm labor: Doppler blood flow assessment of placental and fetal circulation

<scp>P14</scp>.05: Preliminary report of 48‐hours Atosiban administration in spontaneous preterm labor: Doppler blood flow assessment of placental and fetal circulation

Application of oxytocin antagonists in thaw embryo transfer

To study the effects of oxytocin antagonists-atosiban on pregnancy outcome after thaw embryo transfer (TET). Between Jul. and Dec. 2012, a total of 120 women undergoing TET in Reproductive Medical Center, General Hospital of Tianjin Medical University were randomly allocated into atosiban and control group. They were all transferred 2 or 3 top quality embryos at phase of 7-8 cells . Patients in atosiban group were administered by intravenous administration of atosiban before 30 minutes of embryo transfer with a total administered dose of 37.5 mg. In the control group, no special treatment was given before embryo transfer. All patients in 2 groups underwent progesterone luteal support regularly after embryo transfer, then the clinical rate of pregnancy, implantation and early abortion was compared. The clinical pregnancy rate per cycle and implantation rate per transfer were 60% (36/60) and 30.0% (48/160) in the atosiban group, which were higher than 42% (25/60) and 20.3% (31/153) in the control group (all P < 0.05). Early abortion rate was 6% (2/36) in the atosiban group, which was no statistical difference comapring with control group [16% (4/25), P > 0.05]. It was suggested that atosiban treatment before embryo transfer can improve the outcome of pregnancy, and increase clinical pregnancy rate and implantation rate after TET.

The effect of acute stress exposure on ischemia and reperfusion injury in rat heart: Role of oxytocin

Previous studies showed the protective effects of oxytocin (OT) on myocardial injury in ischemic and reperfused rat heart. Moreover, exposure to various stressors not only evokes sudden cardiovascular effects but also triggers the release of OT in the rat. The present study was aimed to evaluate the possible cardioprotective effects of endogenous OT released in response to stress (St), and effects of administration of exogenous OT on the ischemic–reperfused isolated heart of rats previously exposed to St. Wistar rats were divided into six groups: ischemia/reperfusion (IR); St: rats exposed to swim St for 10 min before anesthesia; St+atosiban (ATO): an OT receptor antagonist, was administered (1.5 mg/kg i.p.) prior to St; St+OT: OT was administered (0.03 mg/kg i.p.) prior to St; OT: OT was administrated prior to anesthesia; ATO was given prior to anesthesia. Isolated hearts were perfused with Krebs buffer solution by the Langendorff method and subjected to 30 min of regional ischemia followed by 60 min of reperfusion. The infarct size (IS) and creatine kinase MB isoenzyme (CK-MB) and lactate dehydrogenase (LDH) in coronary effluent were measured. Hemodynamic parameters were recorded throughout the experiment. The plasma concentrations of OT and corticosterone were significantly increased by St. Unexpectedly St decreased IR injury compared with the IR alone group. OT administration significantly inhibited myocardial injury, and administration of ATO with St abolished recovery of the rate pressure product, and increased IS and levels of CK-MB and LDH. These findings indicate that activation of cardiac OT receptors by OT released in response to St may participate in cardioprotection and inhibition of myocardial IR injury.

Role of endogenous oxytocin in cardiac ischemic preconditioning

BackgroundThe aim of the present study is to assess the role of endogenous oxytocin (OT) in cardioprotective effects of ischemic preconditioning (IPC) in anesthetized rat. Materials and methodsAnimals were divided into five groups: 1) ischemia–reperfusion (IR); (n=6), hearts were subjected to 25min regional ischemia and 60min reperfusion, 2) OT; (n=6), oxytocin was administered (0.03μg/kg i.p) 10min prior to ischemia, 3) IPC; (n=7), IPC was induced via a 5min regional ischemia followed by 5min of reperfusion before IR, 4) IPC+ATO (Atosiban); (n=6), atosiban (1.5μg/kg i.p) was used as OT receptor selective antagonist in the beginning of IPC and 5) IR+ATO; (n=6), atosiban was injected 10min prior to ischemia–reperfusion. ResultsIn our experiment, Infarct size was decreased significantly in OT and IPC groups compared to IR (23±1.5% and 19±0.6% vs. 45±2.9% in IR group, P<0.05). Administration of atosiban in IPC+ATO group increased infarct size to 39±0.9% in comparison with OT and IPC groups (P<0.05). The use of OT and IPC prior to ischemia significantly declined ventricular arrhythmias severity in compared to IR group (1.2±0.4 and 1±0.5 respectively, vs. 4±0.4 in IR group, P<0.05). Blockade of OT receptor by atosiban abolished the cardiopreconditioning effects of IPC. ConclusionThis study shows that, in part, the cardioprotective effects of IPC can be induced by endogenous OT.

Oxytocin protects rat heart against ischemia–reperfusion injury via pathway involving mitochondrial ATP-dependent potassium channel

Cardiac preconditioning represents the most potent and consistently reproducible method of rescuing heart tissue from undergoing irreversible ischemic damage. One of the major goals of the current cardiovascular research is to identify a reliable cardioprotective intervention that can salvage ischemic myocardium. The aim of the present study is to evaluate the oxytocin (OT)-induced cardioprotection and the signaling pathway involved with mitochondrial ATP-dependent potassium (mitoKATP) channel in the anesthetized rat heart. Animals were divided into six groups ( n = 6): (1) IR; hearts were subjected to 25 min ischemia and 120 min reperfusion, (2) OT; oxytocin was administered (0.03 μg/kg i.p.) 25 min prior to ischemia, (3) ATO+OT; atosiban (ATO) was used as an OT-selective receptor antagonist (1.5 μg/kg i.p.) 10 min prior to OT administration, (4) ATO; atosiban was used 35 min prior to ischemia, (5) 5HD + OT; 5-hydroxydecanoic acid (5HD) was used as a specific inhibitor of mitoKATP channel (10 mg/kg i.v.) 10 min prior to OT administration, (6) 5HD; 5HD was used 35 min prior to ischemia. Then infarct size, ventricular arrhythmia and creatine kinase-MB isoenzyme (CK-MB) plasma level were measured. Hemodynamic parameters were recorded throughout the experiment. OT administration significantly decreased infarct size, CK-MB plasma level, severity and incidence of ventricular arrhythmia as compared to IR group. Administration of atosiban and 5HD abolished the cardiopreconditioning effect of OT. This study demonstrates that cardioprotective effects of OT are mediated through opening the mitoKATP channels.

Medical therapy in the management of preterm birth

Preterm birth is still the major cause of neonatal mortality and morbidity despite major improvements in neonatal care in the developed countries. Among survivors, the risk of severe consequences is inversely related to the gestational age at delivery. Appropriate antenatal intervention should delay delivery long enough to reduce perinatal consequences related to prematurity. Efficacy of tocolysis varies with gestational age and by the underlying cause of the preterm labour. In this paper we evaluate the use of not steroid anti-inflammatory drugs (NSAIDs) and other tocolytic agents in premature labor as optimal acute first-line treatment. We'll then discuss the use of medical therapy in order to delay delivery beyond 48 hours in selected cases. In a ongoing prospectic randomised trial we consider the association Atosiban – Progesterone to treat spontaneous preterm labor. Our preliminary data suggest that vaginal administration of Progesterone after arrest of uterine activity by atosiban administration could be able to prolong pregnancy in subjects with short cervix.

Tratamiento de la hiperdinamia en el trabajo de parto con atosibán

ObjectiveThe primary objective of the study was to assess the effectiveness of atosiban as a tocolytic drug during labour. A secondary objective was to identify the adverse effects of this drug. Material and methodsA descriptive study was performed including patients who had uterinehyperactivity during labor whether resulting in fetal compromise or not. We included 80 patients from a total of 9017 deliveries assisted during the study period in our hospital (from 1st July 2003 until 31st of August 2004). Numeric data were compared with the sign test and categorical data were compared with χ2 test with Yates’ correction (SPSS v.12 for Windows®). ResultsTotal or partial effectiveness was achieved in 93.8% of the patients. No statistically significant differences were found in relation to blood pressure or maternal heart rate after atosiban administration. No adverse effects were noted in 85% of the patients after drug administration, 13.7% of the patients had nausea and vomiting, and only one patient had symptomatic hypotension. ConclusionsAtosiban is a safe and effective option for the treatment of uterine hyperactivity during labor.

A prospective randomized trial of acute tocolysis in term labour with atosiban or ritodrine

Objective To study the effects of the tocolytics atosiban and ritodrine in term labour. Study design Women in term labour, requiring acute tocolysis, were prospectively randomized for treatment with either atosiban i.v. ( n = 70) or ritodrine i.v. ( n = 70). There were three indications for acute tocolysis: (1) fetal distress followed by continuation of labour, (2) fetal distress followed by emergency caesarean section (CS), and (3) arrest of contractions in women waiting for a secondary CS in the absence of fetal distress. Primary endpoints were maternal blood pressure (MBP) and maternal heart rate (MHR). Secondary endpoints were intra-uterine pressure, fetal heart rate (FHR), 5′-Apgar score and umbilical arterial pH. Results Baseline characteristics did not differ between the study groups. The ritodrine group showed a significant rise in MHR ( p < 0.001), MHR remained unaltered in the atosiban group ( p = 0.31). No significant changes occurred in systolic and diastolic BP in either group. FHR rose by a maximum of 11.6 bpm (8.5%) in the ritodrine group ( p < 0.001) compared to a rise of 4.9 bpm (4.8%) in the atosiban group ( p = 0.27). No differences were found in blood loss and fetal outcome. Compared to baseline, uterine pressure was reduced by a maximum of 55% ( p < 0.001) after ritodrine administration, compared to a maximal reduction of 54% ( p < 0.001) after atosiban administration. These effects did not differ between the two treatment groups. Conclusion Considering the maternal effects, our results suggest a possible role for atosiban bolus in acute tocolysis in term labour.

Involvement of cholecystokinin receptor in the inhibition of gastrointestinal motility by oxytocin in ovariectomized rats

The effects of oxytocin on gastric emptying, gastrointestinal transit, and plasma levels of cholecystokinin (CCK) were studied in ovariectomized rats. Gastrointestinal motility was assessed in rats 15 min after intragastric instillation of a test meal containing charcoal and Na251CrO4. Gastric emptying was determined by measuring the amount of radiolabeled chromium contained in the small intestine as a percentage of the initial amount received. Gastrointestinal transit was evaluated by calculating the geometric center of distribution of the radiolabeled marker. Blood samples were collected for CCK radioimmunoassay. After administration of oxytocin (0.2–0.8 mg/kg), gastric emptying and gastrointestinal transit were inhibited, whereas plasma concentration of CCK was increased in a dose-dependent manner. Atosiban, an oxytocin receptor antagonist, effectively attenuated the oxytocin-induced inhibition of gastric emptying and gastrointestinal transit. However, administration of atosiban alone had no effect on gastric emptying and gastrointestinal transit. The selective CCK1 receptor antagonists, devazepide and lorglumide, effectively attenuated the oxytocin-induced inhibition of gastric emptying and gastrointestinal transit. L-365, 260, a selective CCK2 receptor antagonist, did not alter the oxytocin-induced inhibition of gastric emptying and gastrointestinal transit. These results suggest that oxytocin inhibits gastric emptying and gastrointestinal transit in ovariectomized rats via a mechanism involving the stimulation of CCK release and CCK1 receptor activation.