Oxytocin

A nine-amino-acid hormone made in the hypothalamus, at the base of the brain, and released from the back of the pituitary gland. The chain Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly matches residues 20 to 28 of the human oxytocin precursor in UniProt P01178 letter for letter, and every residue is a standard L-amino acid, so the one-letter code can honestly be printed here. Two chemical details the code cannot show belong beside it: the two cysteines are joined by a sulphur bridge that closes the first six residues into a ring, and the far end of the chain carries an amide cap rather than a free acid. The Pitocin label gives the laboratory-made molecule the empirical formula C43H66N12O12S2 and a molecular weight of 1007.19. Two very different products carry the name: an injection given in maternity wards for childbirth, and a nasal spray, which is an approved medicine in Sweden for helping milk come down when breastfeeding and is authorised in six other European countries, and which is separately sold online under the label of a love or connection hormone.

Sold as

As a controlled drip into a vein, or an injection into a muscle, in hospital. As a nasal spray, which in Sweden is an approved medicine for milk let-down only, and which is authorised in six other European countries. The love-hormone products bought online are nasal sprays and sublingual preparations made up by compounding pharmacies.

Legal status in the EU

An approved prescription medicine across the EU through national authorisations, ATC code H01BB02. The European Medicines Agency's own list of nationally authorised oxytocin products, PSUSA/00002263/202006, runs to eighteen countries and includes both injections and nasal sprays; the nasal sprays listed are in Denmark, Iceland, the Netherlands, Norway, Portugal, Slovenia and Sweden. In Sweden the register holds injections and infusions under the names Syntocinon, Oxytocin Pilum and Oxytocin Grindeks, plus a nasal spray, Oxytocin CD Pharma 6.7 micrograms per dose, whose approved use is starting breastfeeding off, relieving tight breasts, working against blocked milk and preventing and treating early inflammation of the milk glands. No European approval anywhere covers trust, bonding, mood, anxiety or autism. In the United States the picture is narrower: Drugs@FDA lists only injections as currently marketed, and the single nasal application, NDA 012285 Syntocinon nasal solution, is marked discontinued, so the nasal sprays sold there for connection and bonding are compounded products approved by nobody. Oxytocin does not appear anywhere on the WADA 2026 Prohibited List.

Oxytocin switches on its own receptor on the muscle of the womb and on the small muscle cells wrapped around the milk-producing glands in the breast. The womb has few of these receptors early in pregnancy and many by the end, which is why the same amount does almost nothing at one stage and a great deal at another; in the breast the effect is to push milk that is already there down towards the nipple, not to make more of it. It also has a weak grip on the kidney's water-retaining receptor, which is why long infusions alongside large volumes of fluid can waterlog the body and thin the sodium in the blood. Whether enough of a nasal dose reaches a human brain to change social behaviour is genuinely disputed in the field: a 2016 review in Biological Psychiatry concluded that very little of it reaches the fluid around the brain while blood levels rise far above natural, and a 2021 review in Molecular Psychiatry argued from newer work that the nose-to-brain route does deliver a meaningful amount.

Part of the bodyWhat happensHow it is knownKind of evidence

The womb

Oxytocin makes the muscle of the womb squeeze. In a womb close to the end of pregnancy the effect is strong; earlier in pregnancy the womb barely responds, because it has far fewer places for the hormone to attach to. Dripped slowly into a vein it produces contractions that look like natural labour contractions. Given too fast or in too large an amount it produces contractions that do not let go between squeezes, which is what causes the serious harms.

Measured directly and repeatedly for sixty years. The US product information states that after injection into a vein the womb responds almost immediately and settles within an hour, and that after injection into a muscle it responds in three to five minutes and keeps going for two to three hours. The effect on getting a baby born was measured against expectant management and against other methods in a Cochrane review of 61 trials in 12,819 women.

Measured in people

Source [01]Source [16]

Breasts and milk

Oxytocin squeezes the tiny muscle cells around the milk-producing glands, which pushes milk down towards the nipple. This is the let-down reflex, and it is what the nasal spray form is licensed for. It moves milk that is already there. It does not tell the breast to make more milk — that is a different hormone, prolactin.

It is the approved use of the Swedish nasal spray, whose leaflet states it is for starting breastfeeding off, for relieving tight breasts, for working against blocked milk and for preventing and treating early inflammation of the milk glands. Whether it puts more milk into the bottle was tested against a dummy spray in 51 mothers of babies born before 35 weeks: 27 were given the spray and 24 the dummy, and the total weight of milk expressed did not differ between the groups.

Measured in people

Source [03]Source [17]

Water and salt in the body

Oxytocin also makes the kidney hold on to water. It is a weak version of what the closely related hormone vasopressin does, and it matters only when a lot of oxytocin is given for a long time alongside a lot of fluid. The water piles up in the body and thins out the sodium in the blood. Mild cases cause headache, feeling sick, being sick, dizziness and stomach pain. Severe cases cause fits, coma and death.

Stated as a known drug property in the US product information, which says oxytocin has an intrinsic antidiuretic effect that increases how much water the kidney takes back. The severe form is listed in the same label's adverse reactions, where it is tied to slow infusion over a 24-hour period and where maternal death from it is recorded. The UK summary of product characteristics adds that both the mother and the newborn baby have been reported with low blood sodium from it. The Swedish nasal-spray leaflet carries the same warning for long use of high doses of the spray with large amounts of fluid.

Measured in people

Source [01]Source [02]Source [03]

Blood pressure and heartbeat

Pushed quickly into a vein as a single shot, oxytocin drops the blood pressure for a short time. The face goes red and the heart speeds up to compensate. The UK label also warns that it can stretch out one part of the heart's electrical cycle, the QT interval, and that it has been linked to reduced blood flow to the heart muscle. This is one reason the drug is given as a controlled drip rather than a quick push.

Stated in the UK summary of product characteristics, which describes acute short-lasting low blood pressure with flushing and a reflex fast heartbeat after a rapid injection into a vein, and lists heart-rhythm effects. The US product information lists premature ventricular contractions, cardiac arrhythmia and hypertensive episodes among reported reactions in the mother.

Measured in people

Source [01]Source [02]

The brain, and social behaviour

This is where the popular claims live, and it is the part nobody has nailed down. Sprayed up the nose, oxytocin certainly raises the amount circulating in the blood, and it reaches the brain of a laboratory animal. Whether enough of it reaches a human brain to change how a person feels about other people is genuinely disputed among the scientists who study it. What has been tested — trust, reading emotion in faces, social withdrawal in autism, the blunted-feeling symptoms of schizophrenia — has mostly come out no better than a dummy spray.

Studies in people disagree, and the disagreement is about the method itself. One 2016 review in Biological Psychiatry concluded that very little of the large amount sprayed into the nose appears to reach the fluid around the brain, while the amount circulating in the blood rises to levels far above natural, with likely effects on the gut, the heart and the reproductive organs instead. A 2021 review in Molecular Psychiatry, written by researchers in the field, argued the opposite from newer human and animal work — that the nose-to-brain route does deliver a meaningful amount. A separate 2016 analysis of the statistics found that these studies are generally too small to trust, and concluded that most published findings from nasal oxytocin probably do not represent real effects.

Studies in people disagree

Source [11]Source [12]Source [18]

The trial that tested what most people are actually searching for failed. SOARS-B randomly assigned 290 autistic children and teenagers to a nasal oxytocin spray or a dummy spray for 24 weeks; the score on its main social-withdrawal measure fell 3.7 points on oxytocin and 3.5 points on the dummy, a gap of 0.2 points with a 95% confidence interval from 1.5 points better to 1.0 points worse and a p-value of 0.61, and the secondary social and IQ measures generally did not separate either. A Japanese multicentre trial in 106 autistic adult men ended the same way, effect size -0.08 (-0.46 to 0.31, P = 0.69), and its authors wrote that they could not recommend the treatment at that amount and length for the core social symptoms of high-functioning autism in adult men. The 2005 trust experiment that produced the love-hormone story was re-run in 2020 by some of the same authors as a registered replication in 677 young men, designed with more than 95% power, and the effect was not there. The top rung on this page is therefore earned by something else entirely: the injected medicine given in maternity wards, which the World Health Organization lists as an essential medicine. Even there the evidence is older and weaker than the rung's wording suggests. A Cochrane review of 24 trials, 23 of them contributing data on about 10,018 women, found that giving oxytocin after a vaginal birth roughly halved the risk of losing 500 ml of blood or more compared with no contraction drug or a dummy (risk ratio 0.51, 0.37 to 0.72), but graded that low-certainty evidence; a Cochrane review of 61 induction trials in 12,819 women found, in the 3 trials of 399 women that reported it, that 8.4% of women on oxytocin had not given birth vaginally within 24 hours against 53.8% left to wait. Drugs@FDA dates the original Pitocin approval to 19 November 1980. That mismatch between the rung's phrase after large randomised trials and what is actually behind this approval is the defect recorded in STATUS.md 9g, not a grading error on this record.

For the womb, it is fast and short. The US product information states that after injection into a vein the womb responds almost immediately and the response subsides within an hour, and that after injection into a muscle it responds in three to five minutes and keeps responding for two to three hours. The drug is cleared mainly by the kidney and liver and only small amounts leave in the urine unchanged. For milk let-down, the Swedish nasal-spray label works on a scale of minutes before a feed. For the social claims there is no time course to report, because nothing measurable happened: the 24-week children's trial and the 6-week adults' trial both ended level with their dummy sprays.

What was measuredWhat happenedIn whomHow it is known

Losing 500 ml or more of blood after a vaginal birth

About half the risk compared with giving no contraction drug or a dummy: average risk ratio 0.51, 95% confidence interval 0.37 to 0.72. The reviewers graded that low-certainty evidence, because the individual trials were poorly reported and their results varied a lot.

4,162 women across 6 randomised trials, within a Cochrane review of 24 trials, 23 of which contributed data on about 10,018 women having vaginal births

Measured in people

Source [05]

Losing 1,000 ml or more of blood after a vaginal birth

Risk ratio 0.59 against no contraction drug or a dummy, 95% confidence interval 0.42 to 0.83. Also graded low-certainty. The need for a further contraction drug fell too, risk ratio 0.54 (0.36 to 0.80), graded moderate certainty. Whether it changed how many women needed a blood transfusion is unclear: risk ratio 0.88, with a confidence interval from 0.44 to 1.78 that includes no difference at all.

4,123 women across 5 trials for the blood-loss figure; 3,135 women across 4 trials for the extra-drug figure; 3,081 women across 3 trials for transfusion

Measured in people

Source [05]

Not giving birth vaginally within 24 hours of starting induction

8.4% of women on an oxytocin drip against 53.8% of women left to wait, risk ratio 0.16, 95% confidence interval 0.10 to 0.25. More women on oxytocin asked for an epidural: risk ratio 1.10 (1.04 to 1.17). In the one trial that asked, fewer women were dissatisfied with oxytocin induction than with waiting, 5.9% against 13.7%. Against vaginal prostaglandin, oxytocin came off worse on the same 24-hour measure in the two trials reporting it, 70% against 21%.

399 women across the 3 trials that reported this outcome, within a Cochrane review of 61 randomised or quasi-randomised trials in 12,819 women in the third trimester

Measured in people

Source [16]

Social withdrawal in autistic children and teenagers

No difference. The score on the checklist used as the trial's main measure fell by 3.7 points on oxytocin and by 3.5 points on a dummy spray — a gap of 0.2 points, 95% confidence interval 1.5 points better to 1.0 points worse, P = 0.61. The other social measures and an IQ measure generally did not differ either. This is the largest and longest trial ever run on the social claims, and it failed.

290 children and teenagers aged 3 to 17 with autism spectrum disorder, randomly assigned 146 to oxytocin and 144 to a dummy spray, over 24 weeks. 139 and 138 of them contributed to the main analysis

Measured in people

Source [04]Source [19]

Core social difficulties in autistic adults

No difference. The main measure, a rating of social back-and-forth during a structured assessment, fell from 8.5 to 7.7 on oxytocin — but it also fell from 8.3 to 7.2 on the dummy spray, so the gap between the groups was effect size −0.08, 95% confidence interval −0.46 to 0.31, P = 0.69. The authors wrote that they cannot recommend nasal oxytocin on its own at this amount and length for the core social symptoms of high-functioning autism in adult men. Two secondary measures did separate from the dummy, repetitive behaviour and time spent looking at socially meaningful parts of a picture, but they were not what the trial was set up to test.

106 adult men aged 18 to 48 with autism spectrum disorder at multiple Japanese centres, 53 on oxytocin and 53 on a dummy spray, 6 weeks; 103 analysed

Measured in people

Source [13]

Reading emotion in other people's faces, in developmental conditions

Essentially nothing. Every trial pooled here compared oxytocin against a dummy spray. The gap between the two on recognising emotion was Hedges' g = 0.08, which is close to zero and not statistically significant. On empathy the gap was moderate in size but also not significant, g = 0.49. Only one measure, working out what someone else is thinking, reached significance, and it was small, g = 0.21.

466 people with neurodevelopmental conditions across 17 randomised controlled trials

Measured in people

Source [21]

The blunted, withdrawn symptoms of schizophrenia

No consistent effect against a dummy spray. Pooling all nine randomised trials found no significant effect on those symptoms. Higher amounts, above 40 to 80 international units, looked better with a moderate effect size, but that disappeared once one unusual study was removed.

Nine randomised placebo-controlled trials of nasal oxytocin in people with schizophrenia

Measured in people

Source [22]

What happened to women given the most oxytocin during a labour that had started on its own

The paper sorted women into three bands by the total amount of oxytocin they received and reports the comparison for the highest band against women given less. Those women more often bled more than a litre after the birth (odds ratio 2.73, 1.78 to 4.19), more often had a bladder that could not empty (2.19, 1.11 to 4.31), more often had a baby scoring under 7 on the five-minute newborn check (2.89, 1.27 to 6.57) and more often described the birth negatively (1.83, 1.25 to 2.69). Once the authors adjusted for other things that differ between these women, the newborn-score difference no longer held up, while the others did. This is an observed pattern in ordinary care, not a randomised comparison: women who need the most oxytocin are having the hardest labours to begin with.

1,395 women having a first baby at term, labour started on its own, seven hospitals in south-east Sweden, followed prospectively

Measured in people

Source [23]

Trusting a stranger with money

The 2005 experiment that started the whole story reported that oxytocin substantially increased how much money investors handed to a stranger. A registered replication by some of the same authors, designed in advance with more than 95% power to find an effect that size, found none in the condition that copied the original setup. A hint that it might raise trust in people who are low in trust to begin with came out of after-the-fact analysis in the other condition, and the authors said plainly it needs confirming.

677 young men in the 2020 replication, tested in two conditions. The 2005 original's own participant count is not stated in its abstract and could not be checked from an openly readable copy

Studies in people disagree

Source [14]Source [15]Source [20]

Milk expressed by mothers of babies born early

No difference in the total weight of milk expressed between the spray group and the dummy group. The pattern differed — milk came faster at first on oxytocin and then the two groups converged — and a fixed 20-minute test on day 5 found no difference in the weight or the fat content of the milk.

51 mothers of babies born before 35 weeks, 27 given the nasal spray and 24 a dummy spray, used before pumping up to day 5

One small study

Source [17]

The serious harms of the injected form are on its label and are all about the birth: contractions that are too strong or never release, which can tear the womb and cut off the baby's blood supply; harm to the baby including a slow heartbeat, low newborn scores, fits, permanent brain damage and death; severe allergic reactions, which the European label notes particularly in women with a latex allergy; and water poisoning, where the body holds so much water that the sodium in the blood is thinned to the point of fits and coma, with a maternal death recorded on the US label. None of these is given a rate. A quick push into a vein drops blood pressure sharply, so the drug is given as a slow drip. The Swedish nasal spray must not be used during pregnancy, because it can set the womb contracting, and its own label says it is not the right product for starting labour because the effect is too variable; its listed side effects are abnormal womb contractions in up to 1 person in 100 and headache, sickness, hives, throat swelling and irregular heartbeat in up to 1 in 1,000. In the 24-week trial in children, side effects of some kind happened to 82% on oxytocin and 83% on the dummy spray, with more appetite, energy, restlessness and thirst on oxytocin. What is in a compounded nasal spray bought online is verified by nobody.

EffectWhat it feels likeHow often

Water poisoning, with fits and comaSerious

The body holds on to water instead of passing it, and the sodium in the blood is thinned out. It starts as headache, feeling sick, being sick, dizziness, no energy and stomach pain, and at the far end it causes fits, coma and death. It is the reason the drip is not simply left running with plenty of fluid alongside it. The UK label reports it in newborn babies as well as mothers. The same warning is printed on the Swedish nasal-spray leaflet for long use of high doses.

Not counted as a rate. The US product information reports it as having occurred with a slow drip run over a 24-hour period, and records that a mother has died of it.

Source [01]Source [02]

The womb contracting too hard, and tearingSerious

Too much oxytocin, or an unusual sensitivity to it, produces contractions that are too strong, too long, or that never fully release. That can tear the womb, tear the cervix and vagina, cause heavy bleeding afterwards, and cut off the baby's blood supply. The UK label states that inducing labour with a contraction drug, oxytocin included, raises the risk of a serious clotting disorder after the birth.

Not counted as a rate on the label. Listed among reported reactions in the mother, and described in the overdose section as what an excessive amount does.

Source [01]Source [02]

Harm to the babySerious

The label separates the effects caused by the womb squeezing too hard from the effects of the drug reaching the baby. The list includes a slow heartbeat, a low score on the five-minute newborn check, irregular heartbeats, jaundice, bleeding in the back of the eye, permanent brain damage, fits in the newborn and death of the baby. This is why the label requires continuous monitoring by trained staff in a hospital.

Not counted as rates. Listed on the US label as reactions reported in the baby, without numbers attached.

Source [01]

Severe allergic reactionSerious

A whole-body allergic reaction, which can drop the blood pressure dangerously and close off the airway. The UK label notes it specifically in women with a known latex allergy. The Swedish nasal-spray leaflet describes the same picture — sudden rash, trouble breathing, fainting, swelling of the face, tongue or throat — for oxytocin given by any route other than through the gut.

Not counted as a rate. Listed first among reported reactions in the mother on the US label.

Source [01]Source [02]

Blood pressure dropping suddenly, with a red face and a racing heart

Short-lived and self-correcting, but it is the reason the injected form is given as a slow drip. The same label section covers stretching of the heart's QT interval and reduced blood flow to the heart muscle.

Not given as a rate. The UK label ties it to a quick push into a vein rather than to a controlled drip.

Source [02]

Abnormal womb contractions from the nasal spray

The nasal spray is meant for the breast, but the hormone reaches the womb too. This is also why the same leaflet says the spray must not be used during pregnancy.

Uncommon on the Swedish label — up to 1 person in 100.

Source [03]

Headache, feeling sick, being sick, irregular heartbeat, hives and throat swelling from the nasal spray

The rare group on that label runs from the trivial to the dangerous in one list: skin redness, hives, swelling around the voice box, an irregular heartbeat, feeling sick, being sick and headache.

Rare on the Swedish label — up to 1 person in 1,000. Irritation of the lining of the nose is listed with no frequency at all, because nobody has counted it.

Source [03]

What the long nasal-spray trial in children actually found

Four children on oxytocin and three on the dummy stopped the trial because of a side effect; most of the oxytocin stops were for irritability or aggression. One serious event was judged to be caused by the drug: a participant became drowsy while driving and crashed. Average weight gain over the trial was slightly lower on oxytocin than on the dummy, 1.6 kg against 2.3 kg.

Side effects of some kind happened to 82% of the children on oxytocin and 83% of those on the dummy spray, over 24 weeks. The individual things that were more common on oxytocin were: more appetite (16% against 10%), more energy (10% against 3%), restlessness (8% against 2%), the caregiver noticing weight loss (7% against 3%), more thirst (6% against 3%), poorer attention (6% against 3%) and aching muscles (3% against 1%).

Source [04]

These are the amounts the studies below gave their participants, and they are here as facts about those studies. They are not a recommendation, not a starting point and not a range to pick from. What a person should take, if anything, is a question for a doctor who knows them.

SOARS-B, the 24-week trial of nasal oxytocin for social withdrawal in autistic children and teenagers — the trial that found no difference from a dummy spray

Sprayed into the nose. The trial's target was 48 international units a day, and across the trial the total daily amounts given ranged from 8 to 80 international units

24 weeks

Source [04]

The Japanese multicentre trial of nasal oxytocin for core social symptoms in autistic adults — also no difference from a dummy spray on its main measure

48 international units a day, sprayed into the nose

6 weeks

Source [13]

The randomised trial of nasal oxytocin in mothers expressing milk for babies born early

One 100-microlitre spray dose before each session of expressing milk with an electric pump, against a dummy spray

Up to day 5 after the birth

Source [17]

What people report

• Whether nasal oxytocin does anything at all to how a person feels about other people — the two largest trials ended level with a dummy spray, and the field's own reviewers disagree about whether enough of it reaches a human brain to matter.
• How much of a sprayed dose reaches the fluid around the brain in a person: one review concludes very little does, another concludes the nose-to-brain route works, and the measurement has not settled the argument.
• Whether the after-the-fact hint that it raises trust in people who are low in trust to begin with is real — the only follow-up so far is a preprint that has not been through peer review.
• Whether any of the popular claims about calm, connection, bonding or anxiety would survive a trial, because no adequately sized trial of them has been published.
• What a compounded oxytocin nasal spray bought online actually contains: nobody tests it, and the only nasal oxytocin product the United States ever approved is marked discontinued.
• What repeated nasal oxytocin does over years. The longest randomised exposure on record is 24 weeks, in children.
• Whether it is safe to give repeatedly to a developing brain — the 24-week children's trial reported similar overall side-effect rates to the dummy spray, and nothing longer exists.
• How often the womb-tearing and baby-harming reactions on the label actually happen — they are listed as reported events with no rate attached to any of them.
• How often water poisoning happens, for the same reason: the label describes the mechanism and records a maternal death, but no rate.
• Whether the extra problems seen in women given the most oxytocin during labour are caused by the drug or by the difficult labours that led to it being given — the study is observational and cannot separate the two.
• Which infusion regimen is best. Cochrane rated most of the induction and prophylaxis evidence low or very low certainty, and its authors explicitly called for trials of optimal dose and route with outcomes such as maternal death included.
• Whether the nasal spray does anything useful for milk supply as opposed to milk let-down: the one randomised trial, in 51 mothers of premature babies, found no difference in the total milk expressed.
• Whether it helps depression after birth, mother-and-baby bonding, or anxiety, none of which has a trial of the size and length that the autism question got.
• What the American approvals would look like if they were assessed today: Drugs@FDA dates the original Pitocin approval to 19 November 1980, and the nasal solution's application is so old that the database holds no submission record for it at all.

Does oxytocin nasal spray actually work?

It depends entirely on what you want it to do. Helping milk come down when breastfeeding is what the Swedish label covers, and a nasal spray is authorised in six other European countries as well. For trust, bonding, social confidence or anxiety, the honest answer is no: the two largest and longest trials, one in 290 autistic children over 24 weeks and one in 106 autistic adult men over 6 weeks, both ended level with a dummy spray on the thing they set out to measure.

Source [03]Source [04]Source [13]

Is oxytocin really the love hormone?

That name comes from one influential 2005 experiment in which men given a nose spray handed more money to a stranger in a game, plus a great deal of animal research on bonding. When some of the same scientists ran the experiment again in 2020, properly registered in advance and with enough people to be sure, the effect was not there. Reviewers who went back over the whole literature concluded that it does not add up to reliable evidence that human trust is caused by oxytocin at all.

Source [14]Source [15]Source [24]

Is oxytocin the same thing as Pitocin?

Yes. Pitocin is a brand name for laboratory-made oxytocin injection in the United States; Syntocinon is the equivalent name in Europe. It is the same nine-amino-acid molecule the body makes. The difference people are usually reaching for is not the molecule but the route and the amount: a controlled drip into a vein during labour is a very different thing from what the body releases on its own.

Source [01]Source [25]

Can you buy oxytocin, and is it legal?

In Sweden and across the EU it is a prescription-only medicine in every form, including the nasal spray, and the injected form is a hospital drug. In the United States the only nasal oxytocin application on the regulator's own database is marked discontinued, so the sprays sold online there are made up by compounding pharmacies rather than approved by anyone. Advertising an unapproved medicine to the public is illegal in Sweden under the Medicinal Products Act (2015:315).

Source [07]Source [08]Source [26]

What are the side effects of oxytocin?

For the drip used in labour, the dangerous ones are the womb contracting too hard — which can tear it and cut off the baby's blood supply — and water building up in the body until the salt in the blood is dangerously thin, which can cause fits and coma. Severe allergic reactions are also on the label. For the nasal spray, the Swedish label lists abnormal womb contractions in up to 1 person in 100 and headache, sickness, hives, throat swelling and irregular heartbeat in up to 1 in 1,000. In the 24-week children's trial, side effects of some kind happened to 82% on oxytocin and 83% on the dummy spray.

Source [01]Source [03]Source [04]

Does oxytocin help autism?

The best evidence says no. SOARS-B randomised 290 autistic children and teenagers to a nasal spray or a dummy for 24 weeks; the social-withdrawal score fell 3.7 points on oxytocin and 3.5 points on the dummy, a gap of 0.2 points with a p-value of 0.61. A Japanese trial in 106 autistic adults came out the same way. A 2024 pooled analysis of the smaller trials did find a small average benefit on social outcomes, but its authors reported that publication bias was probably inflating it.

Source [04]Source [13]Source [27]

Oxytocin vs desmopressin — what is the difference?

They are cousins. Both are nine-amino-acid hormones from the back of the pituitary gland, and both have a ring closed by a sulphur bridge. Oxytocin acts mainly on the womb and the breast; desmopressin is a modified copy of the other one, vasopressin, and acts on the kidney to make the body hold water. The overlap is what causes trouble: at high doses over a long time, oxytocin also makes the kidney hold water, which is how water poisoning happens.

Source [01]Source [09]

Is oxytocin banned in sport?

No. The World Anti-Doping Agency's 2026 Prohibited List does not name oxytocin anywhere. Its cousin desmopressin is named, under diuretics and masking agents, because holding water in the body dilutes the blood and hides blood doping — but that section names desmopressin and not oxytocin. Note that the section is written as a non-exhaustive list ending in "and other substances with a similar chemical structure or similar biological effect(s)", so an athlete should not treat an absence from the list as a clearance.

Source [10]

Each letter represents one amino acid.

1. [01]DailyMed – PITOCIN (oxytocin injection, USP), US prescribing information: indications, contraindications, warnings, adverse reactions and the statement that it is not indicated for elective induction of labor
2. [02]Oxytocin 10 IU/ml Solution for Infusion – Summary of Product Characteristics (emc), sections 4.1, 4.3, 4.4 and 4.8, text revised 10 February 2025 (2025)
3. [03]Swedish Medical Products Agency – patient leaflet for Oxytocin CD Pharma 6.7 micrograms/dose nasal spray (in Swedish): approved use, pregnancy contraindication, water poisoning warning and side-effect frequencies
4. [04]Sikich L et al. Intranasal Oxytocin in Children and Adolescents with Autism Spectrum Disorder. New England Journal of Medicine 2021;385:1462-1473 (SOARS-B; 290 children, primary outcome -3.7 vs -3.5 on placebo, P = 0.61) (2021)
5. [05]Salati JA, Leathersich SJ, Williams MJ, Cuthbert A, Tolosa JE. Prophylactic oxytocin for the third stage of labour to prevent postpartum haemorrhage. Cochrane Database of Systematic Reviews 2019, CD001808 (24 trials, about 10,018 women) (2019)
6. [06]WHO Model List of Essential Medicines, 24th list (2025), section 22.3 Uterotonics – oxytocin injection 10 IU in 1 ml (2025)
7. [07]European Medicines Agency – list of nationally authorised medicinal products, active substance oxytocin, PSUSA/00002263/202006, 11 February 2021 (injections and nasal sprays across sixteen countries) (2021)
8. [08]Drugs@FDA via the openFDA interface – all US oxytocin applications: original Pitocin approval 19 November 1980; NDA 012285 Syntocinon nasal solution marked Discontinued
9. [09]UniProt P01178 – oxytocin-neurophysin 1: oxytocin is residues 20-28 (CYIQNCPLG), disulfide bond 20-25, glycine amide at residue 28
10. [10]WADA International Standard Prohibited List 2026 – full text searched; oxytocin does not appear anywhere on it (2026)
11. [11]Leng G, Ludwig M. Intranasal oxytocin: myths and delusions, Biological Psychiatry 2016;79(3):243-50 (2016)
12. [12]Quintana DS et al. Advances in the field of intranasal oxytocin research: lessons learned and future directions for clinical research, Molecular Psychiatry 2021 (2021)
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