Oxytocin

Oxytocin is a hormone the body makes, nine amino acids long, and it is one of the few things in this reference that is a real approved drug. The approval is an injection used in childbirth: starting or reinforcing labour, helping the uterus empty, and controlling bleeding after delivery. Its label allows exactly two ways in, a drip into a vein or a shot into a muscle, and it is dosed in international units rather than milligrams. What is sold for bonding, trust, social ease and sleep is a nasal spray mixed to order by a compounding pharmacy. There was once an approved American nasal oxytocin; its record is still in the government database, marked discontinued.

In the body it acts on the uterus and the breast, and in the brain it is involved in social and pair bonding behaviour, which is where the selling comes from. The bonding reputation starts with an infusion directly into a rodent's brain: in female prairie voles, oxytocin released into the brain ventricles produced a preference for the partner, while the same drug given under the skin did nothing. So the question was always how to get it in, and that question is genuinely unsettled. It also does not last, at a blood half life of about 1 to 6 minutes.

Bonding, trust, social anxiety, sexual effect and sleep. The trial record for those uses is mostly autism, and the two largest randomised trials I found both missed their primary endpoint, prespecified in the larger of the two. A 2021 systematic review counted 38 randomised trials between 1990 and 2010 across 1,529 participants, 79 percent male, and 8 percent of them people with developmental or mental health difficulties. What that record does not contain is the person buying a compounded spray for bonding or for sleep.

The premise under the whole spray market is that sniffing it reaches the brain, and that is argued over inside the papers that measured it rather than settled. The founding human paper for the nose to brain route did not test oxytocin at all; it gave a melanocortin fragment, vasopressin and insulin. Oxytocin itself was measured eleven years later in neurology inpatients already having a spinal tap, one sample each, and nothing measurable had happened at 45 or 60 minutes, with only the three men sampled at 75 minutes above the placebo group. Since then macaque work found no advantage of the nose over a vein, a human imaging study explained the brain blood flow change entirely by the rise in the bloodstream, and blocking the nasal blood route removed most of an electrical brain effect. Pushing the other way, fluid sampled straight out of rodent brain regions rose after a nasal dose, and reviews split on the same literature. The honest position is that it is unresolved, and blood oxytocin, which is what nearly every study and every sales page measures, did not track the spinal fluid in the one human study that measured both.

The serious harms on the approved label belong to labour rather than to the molecule: maternal deaths from blood pressure episodes, bleeding around the brain, rupture of the womb, and fetal deaths, with oxytocic drugs injected for induction. The harm that belongs to the molecule is water intoxication, which has killed, with convulsions and coma during a slow infusion over 24 hours, and the label attaches a rate to it that works out at 2.4 to 3 units an hour sustained into a vein. That is a different kind of exposure from six squirts of a spray. On long term risk the label's own answer is that the studies were not done: none on carcinogenicity or mutagenicity, and no information on fertility. For the nasal route in research settings the record is unremarkable, and a 2011 review says so in three numbered points, at 18 to 40 units for short term use in controlled research. The best powered posted safety numbers are from the largest autism trial, where over 24 weeks serious adverse events ran 2 of 146 on oxytocin against 1 of 144 on placebo.