What it is
Oxytocin is a nine-amino-acid hormone: Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly, with the final glycine amidated. The two cysteines are joined by a disulfide bond, which folds the first six residues into a small ring with a three-residue tail (UniProt P01178).
The body makes it in the hypothalamus as part of a longer 125-residue precursor, which also carries a carrier protein called neurophysin 1, and releases it from the posterior pituitary. Its closest relative is vasopressin, which differs at two positions and does a quite different job — holding water in the kidney and raising blood pressure.
What it does in the body
Two roles are established beyond dispute:
- Uterine contraction. Oxytocin drives contractions during labour and clamps down the uterus after delivery, which limits bleeding.
- Milk let-down. Suckling triggers its release, and it contracts the cells around the milk ducts.
A third area — social behaviour, pair bonding and maternal care — is well documented in animal research, particularly in voles and rodents. That animal literature is where the "love hormone" nickname comes from, and it is a different body of evidence from what has been shown in people.
The approved medicine
Oxytocin is an approved US prescription drug, and has been for decades. Drugs@FDA lists (openFDA query, 2026-09-17):
| Product | Application | Sponsor | First approved | Status |
|---|---|---|---|---|
| PITOCIN | NDA 018261 | Par / PH Health | 1980-11-19 | Prescription |
| Oxytocin | NDA 018248 | Fresenius Kabi | 1980-07-09 | Prescription |
| Oxytocin | ANDA 200219 | Hikma | 2013-02-13 | Prescription |
| SYNTOCINON | NDA 018245 | Novartis | — | Discontinued |
All are injections. The Pitocin label (effective 2026-05-06) approves it for:
- before delivery — starting labour when there is a medical reason (Rh problems, maternal diabetes, pre-eclampsia at or near term, ruptured membranes), strengthening labour in selected cases of uterine inertia, and as an adjunct in incomplete or inevitable abortion;
- after delivery — producing contractions in the third stage of labour and controlling postpartum bleeding.
The label opens with an Important Notice: Pitocin is not indicated for elective induction of labour — induction with no medical reason — because the data are inadequate to weigh benefit against risk.
On dosing, the label says the dose "is determined by the uterine response and must therefore be individualized and initiated at a very low level", that IV drip is the only acceptable parenteral method for induction or stimulation, and that the standard solution is 10 units in 1,000 mL of saline or Ringer's lactate — 10 milliunits per mL — given by infusion pump. It notes the hormone is made synthetically so that it cannot be contaminated with vasopressin.
The nasal spray, and the trial that tested it properly
Outside the hospital, oxytocin is sold mainly as a nasal spray for bonding, trust, social anxiety and autism. No such product is approved in the United States.
The idea was not baseless. Small laboratory studies gave people a single nasal dose and measured trust, eye gaze or emotion recognition in a task, and several reported effects. Small clinical trials in autism reported improvements. On that basis, as the trial paper itself notes, oxytocin was already being given to many children with autism in clinical practice.
Then SOARS-B tested it at scale (Sikich et al., New England Journal of Medicine, 2021; DOI 10.1056/NEJMoa2103583):
| Oxytocin | Placebo | |
|---|---|---|
| Enrolled | 146 | 144 |
| Change in social withdrawal score at 24 weeks | −3.7 | −3.5 |
| Difference | −0.2 (95% CI −1.5 to 1.0), P = 0.61 |
It was randomised, placebo-controlled, 24 weeks long, funded by the National Institute of Child Health and Human Development, in 290 children and adolescents aged 3 to 17, at a target of 48 IU a day. Secondary outcomes — two further measures of social function and an abbreviated IQ — generally did not differ either. Adverse events were similar in both groups.
This is the shape of result this library reports most often: a plausible mechanism, promising small studies, and then a large, well-run trial that finds nothing. The small studies are not erased by it, but the claim they supported is much weaker than it was.
Where it stands
A drug with an enormous literature — PubMed indexes 33,892 oxytocin records and 2,133 randomized controlled trials (E-utilities, 2026-09-17) — and 287 registered studies matching intranasal oxytocin on ClinicalTrials.gov. Its obstetric use is established and approved. Its social and psychiatric uses remain research questions, and the largest test of the most-promoted one was null.
Related entries in this library: PT-141 is the peptide sold for sexual desire, with an actual approval; kisspeptin's entry covers another hypothalamic peptide at the centre of reproductive signalling; VIP is another neuropeptide whose reputation runs ahead of its human trials.
Last checked
2026-09-17. The current Pitocin label and Drugs@FDA records were read through the openFDA API, UniProt P01178 through the UniProt REST API, the SOARS-B abstract through PubMed with its DOI verified by content negotiation, and the ClinicalTrials.gov and PubMed counts, all on that date.