Oxytocin

A natural hormone made in the brain and released from the posterior pituitary. It differs from vasopressin, the body's water-retaining hormone, at two positions.

Binds oxytocin receptors on uterine muscle and on cells around milk ducts, causing contractions and milk ejection. At large amounts it acts like vasopressin, increasing water reabsorption in the kidney. In animals it modulates social and stress circuits; how much nasal oxytocin reaches the human brain is unclear.

Decades of clinical use and trials support the approved injection for labor and postpartum bleeding, and it is on the WHO Essential Medicines list. Nasal research has been less consistent: the largest autism trial (290 children, NEJM 2021) found no benefit over placebo, and early positive findings on trust and social cognition have not held up in critical reviews. Small trials in obesity have not shown meaningful weight change. Animal work links it to bonding, maternal behavior, feeding and stress.

The approved label warns of water intoxication and low sodium with prolonged infusion, which has caused seizures, coma and maternal deaths, plus uterine rupture, arrhythmias and anaphylaxis. Nasal studies reported nasal irritation, headache and nausea at rates similar to placebo, and some pilot participants developed prolonged QTc. Approved products are labeled in USP units, not milligrams.

FDA-approved as Pitocin and generic oxytocin injection for hospital obstetric use only (label revised March 2026); no approved nasal product was found, and approval does not cover research material. As a component of an approved drug it is 503A-eligible with a prescription and is not on the Category 2 safety-risk list. Not named on the 2026 WADA list.