Oxytocin comparative studies

Insel TR Oxytocin—a neuropeptide for affiliation evidence from behavioral, receptor autoradiographic, and comparative studies. Psychoneuroendocrinology 17 3-35, 1992... 

Bugalho, A. Bique, C. Machungo, F. Bergstrom, S. A comparative study of vaginal misoprostol and intravenous oxytocin for induction of labour. Gyn. Obstet. Invest. 1995, 39, 252-256. 

In a retrospective analysis of 2774 women who had had one prior cesarean delivery, there was a 1% incidence of uterine rupture in women who were given oxytocin, compared with 0.4% in non-augmented controls with spontaneous labor (12). Six women needed emergency hysterectomy. The odds ratio for uterine rupture in the oxytocin-treated women was 4.6 by logistic regression analysis (Cl = 1.5,14). The small number of events limited the study it had only 30% power to detect changes of that magnitude. However, it is reasonable to proceed cautiously, with... 

Comparative studies Oxytocin versus carbetocin Oxytocin 5 lU was compared with carbetocin 100 micrograms in a randomized trial in 377 women. There were similar adverse reactions in the two groups, nausea being the most common (10/188 and 12/189 respectively) [49 "]. 

Observational studies The use of oxytocin in low income countries has been reviewed [28 ]. The use of oxytocin compared with no use of oxytocin in normal labor had a relative risk of 1.9 for stillbirth. The adjusted relative risk for neonatal resuscitation was 2-5.6. Oxytocin is useful for the... 

Mukta M, Sahay PB. Role of misoprostol 600 meg oral in active management of third stage of labor a comparative study with oxytocin 10 lU i.m. J Obstet Gynaecol India 2013 63(5) 325-7. Epub 2014/01/17. 

By comparing time-resolved and steady-state fluorescence parameters, Ross et alm> have shown that in oxytocin, a lactation and uterine contraction hormone in mammals, the internal disulfide bridge quenches the fluorescence of the single tyrosine by a static mechanism. The quenching complex was attributed to an interaction between one C — tyrosine rotamer and the disulfide bond. Swadesh et al.(()<>> have studied the dithiothreitol quenching of the six tyrosine residues in ribonuclease A. They carefully examined the steady-state criteria that are useful for distinguishing pure static from pure dynamic quenching by consideration of the Smoluchowski equation(70) for the diffusion-controlled bimolecular rate constant k0,... 

The effects of oral PGE2 administration (0.5-1.5 mg/h) have been compared with those of intravenous oxytocin and oral demoxytocin, an oxytocin derivative, in the induction of labor. Oral PGE2 is superior to the oral oxytocin derivative and in most studies is as efficient as intravenous oxytocin. Oral PGF2(X causes too much gastrointestinal toxicity to be useful by this route. 

Examples of the way these two entirely different approaches compliment each other are developing in conformation studies with the hormones angiotensin, oxytocin, and vasopressin. In 1964 Craig, Harfenist, and Paladini (7) published the comparative half-escape times shown in Table I in 0.01N acetic acid and another series in Table II using a different membrane less porous and not as selective as the first. Oxytocin and vasopressin are cyclic octapeptides with an S-S linkage closing the ring at the 1-6 positions (5, 6). Their size is thus limited except for the side... 

It was postulated from the comparative data in Tables I and II and other observations that angiotensin had a definite compact conformational structure even though it is a linear peptide and should be a random coil. Tritium-exchange studies (39), CD (40), and NMR evidence (41, 42) now give support to this view. NMR studies with angiotensin, oxytocin, and vasopressin thus far have not indicated conformational restriction on the benzene rings, but the thin-film dialysis data are inconsistent with any conformation in which these bulky groups are extended from the otherwise compact conformation. 

The mobility of the acyclic terminal tripeptide in lysine vasopressin is larger compared to that in oxytocin, which is coincident with a model suggested from H NMR studies [856]. 

High-dose and low-dose oxytocin have been compared in augmentation or induction of labor (19). There was large variation in the doses given in the studies reviewed, particularly among the high doses used. In some studies... 

Plasma oxytocin has been shown to be reduced in autistic children and moreover, levels of oxytocin were correlated with social impairment (Modahl et al., 1998). A follow-up study using the same subjects found that the autistic children had higher levels of the precursor of oxytocin when compared with controls, suggesting that reduced plasma oxytocin in autistic children may be related to how oxytocin is processed (Green et al., 2001). Preliminary studies have demonstrated that infusion with oxytocin can reduce repetitive behaviors such as... 

A peptide analog that competitively inhibits the interaction of oxytocin with its membrane receptor, atosiban (tractocile), has been introduced in a number of countries for the treatment of preterm labor. Atosiban decreases the frequency of uterine contractions and increases the number of women who remained undelivered. Its efficacy is comparable to /3 adrenergic agonists but the incidence of side effects is lower. It should be noted, however, that studies to date have failed to demonstrate a significant improvement in infant outcome when preterm labor is delayed. 

In a study of pregnant women with premature rupture of the membranes, who were between weeks 37 and 42 of gestation, administration of castor oil increased the rates of spontaneous labor, decreased the need for cesarean section, and decreased the need for labor induction with oxytocin as compared to women not administered castor oil. No significant adverse events were reported in the mothers. The... 

The conformation of the COOH-terminal tripeptide of vasopressin has been studied via CD and nmr spectroscopy and compared with the analogous oxytocin peptide (Erie et a/., 1976). 

Patients who received oxytocin infusions during labor were randomized to placebo or an additional bolus dose of 5 lU at the time of cesarean section [59. The extra oxytocin caused a fall in systolic blood pressure of >20% from baseline in 18 of 70 patients within 5 minutes compared with 10 of 73 who were given placebo however, the difference did not reach statistical significance. The study may have been imderpowered to detect a significant difference in adverse reactions, since that was not the primary end-point. 

Drug dosage regimens Two doses of oxytocin doses (5 lU as a bolus versus 5 lU as a bolus followed by 30 lU by infusion over 4 hours) have been compared in a randomized, placebo-controlled study in 720 women at risk of post-partum hemorrhage undergoing elective cesarean section there was more blood loss over a liter in those who received a bolus dose (13% versus 5.0%) and no difference in adverse reactions [60 ]. 

Table II represents the author s estimate of the physiological significance of the in vitro findings with hormones reported in the literature, as based upon the above criteria. It will be seen that a sizable number of hormones exert in vitro effects which are comparable in their essentials to the physiological effects observed in vivo. Among these are seen all chemical classes of hormones with the exception of the steroids protein— insulin polypeptides—ACTH, antidiuretic hormone (ADH), oxytocin, and glucagon or hyperglycemic factor (HGF) and amino acid derivatives —epinephrine and nor-epinephrine. The remaining hormones listed, in which physiologically meaningful in vitro results have not been as yet achieved, may be subdivided into two groups one, wherein little work has been attempted (as with parathormone, prolactin, etc.) the other, wherein extensive in vitro studies have been carried out.

The S-p-methoxybenzyl thioether of cysteine has also been utilized in a synthesis of oxytocin (Table 7.1). In these studies [15, 17] the thioether was removed with refluxing trifluoroacetic acid in the presence of anisole. The ability of trifluoroacetic acid to cleave the S-/>-methexybenzyl group (albeit at reflux) is probably a reflection of the increased stability of the cation as compared to the benzyl carbonium ion. The activity of the oxytocin obtained by this route (after air oxidation of... 

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