Methylergometrine (other names include methylergonovine, methylergobasin, methergine, and D-lysergic acid 1-butanolamide) is a synthetic analogue of ergonovine, a psychedelic alkaloid found in ergot, and many species of morning glory. In general, the effects of all the ergot alkaloids appear to results from their actions as partial agonists or antagonists at adrenergic, dopaminergic, and tryptaminergic receptors. The spectrum of effects depends on the agent, dosage, species, tissue, and experimental or physiological conditions. All of the alkaloids of ergot significantly increase the motor activity of the uterus. After small doses contractions are increased in force or frequency, or both, but are followed by a normal degree of relaxation. As the dose is increased, contractions become more forceful and prolonged, resting tonus is markedly increased, and sustained contracture can result. Methylergometrine acts directly on the smooth muscle of the uterus and increases the tone, rate, and amplitude of rhythmic contractions through binding and the resultant antagonism of the dopamine D1 receptor. Thus, it induces a rapid and sustained tetanic uterotonic effect which shortens the third stage of labor and reduces blood loss. Methylergometrine is used for the prevention and control of excessive bleeding following vaginal childbirth.

Epelsiban (GSK557296), a pyridyl-2,5-diketopiperazine, is a potent, highly selective, and orally bioavailable non-peptide oxytocin receptor antagonist. GlaxoSmithKline was developing epelsiban for the treatment of women infertility due to adenomyosis and premature ejaculation.

PF-3274167 (Cligosiban) is a potent, selective, brain penetrant oxytocin receptor antagonist. Cligosiban interrupts the expulsion phase of ejaculation by reducing the normal bulbospongiosum burst pattern and reducing the expulsions that accompany bursts. Cligosiban represents a promising compound to test the clinical hypothesis that antagonism of central oxytocin receptors may be of therapeutic benefit in the treatment of premature ejaculation. [11C]PF-3274167 is not a suitable tracer for imaging of OTR in rat brain, probably because of a too low affinity for this receptor in addition to a poor brain penetration. PF-3274167 had been in phase I clinical trial for the treatment of sexual function disorders and urinary incontinence. However, this research has been discontinued.

Barusiban, a long-acting oxytocin antagonist, has been studied to stop preterm labor in pregnant women at late gestational age. The experiments failed to demonstrate the effectiveness and were discontinued. However, barusiban participates in phase II clinical trials for female infertility.

Retosiban is a small molecule oxytocin receptor antagonist that is under evaluation for treatment of premature labor. Retosiban was found to be safe in healthy non-pregnant volunteers in phase I studies. Intravenous retosiban also had good safety and tolerability in phase II studies and was suggested to prolong pregnancies in women with preterm labor. Phase III studies have been conducted to demonstrate the efficacy of retosiban to prolong pregnancy and improve neonatal outcomes, and compare effects with a similar drug atosiban, but these studies were terminated in 2018 (not due to adverse events).

Ergonovine (also known as ergometrine) is the active water soluble component of ergot of rye. Ergonovine is being used as a maleate salt to prevent or treate postpartum haemorrhage and postabortion haemorrhage. Ergonovine stimulates alpha-adrenergic and serotonin receptors, thus activating contractions of uterine and vascular smooth muscle. Ergonovine may have depressant effect on CNS system as it binds to dopamine receptors.

Atosiban (brand name Tractocile) is a competitive antagonist of human oxytocin at receptor level. In rats and guinea pigs, atosiban was shown to bind to oxytocin receptors, to decrease the frequency of contractions and the tone of the uterine musculature, resulting in a suppression of uterine contractions. Atosiban was also shown to bind to the vasopressin receptor, thus inhibiting the effect of vasopressin. Tractocile is indicated to delay imminent pre-term birth in pregnant adult women with: − regular uterine contractions of at least 30 seconds duration at a rate of ≥ 4 per 30 minutes − a cervical dilation of 1 to 3 cm (0-3 for nulliparas) and effacement of ≥ 50% − a gestational age from 24 until 33 completed weeks − a normal foetal heart rate. Atosiban does not have U.S. Food and Drug Administration (FDA) approval for use in the United States.

Carbetocin is a synthetic analogue of human peptide hormone, oxytocin. Like oxytocin, it stimulate oxytocin receptors and is used to facilitate childbirth. The drug is being marketed in Europe under the name Pabal for the prevention of uterine atony following delivery of the infant by Caesarean section. If untreated by carbetocin, uterine atony may lead to postpartum haemorrhage.

Demoxytocin is a synthetic analog of a peptide hormone oxytocin. The drug possesses higher oxytocin and lower vasopressin activity than oxytocin and is not broken down by leucylaminopeptidase or serum oxytocinase. Demoxytocin is administered as a buccal tablet formulation and is used for the induction of labor in overdue pregnancies, to prevent and treat puerperal mastitis and to promote lactation.

More than a century ago, Sir Henry Dale demonstrated that a component of the pituitary causes contractions of the mammalian uterus, hence his coining the term “oxytocic,” derived from the Greek for “quick birth,” for its activity. The discovery that a component of the pituitary causes milk secretion followed within a few years. By 1930, oxytocin was separated from vasopressin into pitocin and pitressin, respectively, at Parke Davis and made available for research. That a single peptide was responsible for these uterine and mammary actions was definitively confirmed upon the sequencing and synthesis of the peptide, 9 amino acids in length. Vincent du Vigneaud was awarded a Nobel Prize for this work. Oxytocin is indicated for the initiation or improvement of uterine contractions, where this is desirable and considered suitable for reasons of fetal or maternal concern, in order to achieve vaginal delivery. Oxytocin is indicated to produce uterine contractions during the third stage of labor and to control postpartum bleeding or hemorrhage. Uterine motility depends on the formation of the contractile protein actomyosin under the influence of the Ca2+- dependent phosphorylating enzyme myosin light-chain kinase. Oxytocin promotes contractions by increasing the intracellular Ca2+. Oxytocin has specific receptors in the myometrium and the receptor concentration increases greatly during pregnancy, reaching a maximum in early labor at term. The Oxytocin receptor is a typical class I G protein-coupled receptor that is primarily coupled via G(q) proteins to phospholipase C-beta. The high-affinity receptor state requires both Mg(2+) and cholesterol, which probably function as allosteric modulators. The agonist-binding region of the receptor has been characterized by mutagenesis and molecular modeling and is different from the antagonist binding site. The function and physiological regulation of the Oxytocin system is strongly steroid dependent.