Oxytocin is a nine-amino-acid hormone made in the brain. It is FDA approved as Pitocin, an injection used in hospitals to start or strengthen labor contractions. Other uses, including nasal sprays, are off-label or experimental.
Also known as: Pitocin.
Pitocin is a ready-made solution (10 USP units per mL in a 10 mL vial) for hospital use, with no mixing. Powder vials of oxytocin are usually labeled 2 mg or 5 mg.
Water and syringe-unit charts by vial size: 2 mg · 5 mg
Here is the math for a 2 mg vial mixed with 2 mL of bacteriostatic water, drawing 100 mcg with a U-100 insulin syringe (1 mL = 100 units).
2 mg ÷ 2 mL = 1 mg/mL100 mcg ÷ 1 mg/mL = 0.1 mL0.1 mL × 100 = 10 units| Amount | Volume | U-100 syringe |
|---|---|---|
| 50 mcg | 0.05 mL | 5 units |
| 100 mcg | 0.1 mL | 10 units |
| 200 mcg | 0.2 mL | 20 units |
Adding more water doesn't change how much oxytocin is in the vial. It only spreads it over more liquid, so each draw is bigger and easier to read.
| Water added | Concentration | Volume | U-100 syringe |
|---|---|---|---|
| 1 mL | 2 mg/mL | 0.05 mL | 5 units |
| 2 mL | 1 mg/mL | 0.1 mL | 10 units |
| 3 mL | 666.7 mcg/mL | 0.15 mL | 15 units |
| 5 mL | 400 mcg/mL | 0.25 mL | 25 units |
For any other vial size or amount, the free peptide reconstitution calculator works backwards from the amount you want and suggests a water volume that lands on a clean syringe mark.
The FDA Pitocin label gives a plasma half-life of about 1 to 6 minutes. That is for the hospital drug given into a vein or muscle, so we do not list it as a half-life for other routes. A 2025 study using a specific assay found that only about 0.7% of a nasal dose reached the blood.