Oxytocin

The label records measured pharmacology rather than a controlled trial programme. Measured pharmacokinetics give a plasma half-life of about 1 to 6 minutes, shortened in late pregnancy and during lactation, with uterine response almost immediate after intravenous administration and within 3 to 5 minutes after intramuscular injection. Measured pharmacodynamics record that receptor concentration in the myometrium rises greatly during pregnancy to a maximum in early labour at term, so the response to a given dose varies with that concentration. Studies of maternal plasma concentrations during infusion showed that rates up to 6 milliunits per minute give the same levels found in spontaneous labour. Dosing is titrated against monitored variables including uterine tone, contraction amplitude and frequency, and fetal heart rate.

What is not established

The label opens with a notice stating that, because the available data are inadequate to evaluate the benefit-to-risk considerations, this product is not indicated for elective induction of labour. There are no animal or human studies of carcinogenicity or mutagenicity, no information on its effect on fertility, and animal reproduction studies have not been conducted.

What distinguishes Oxytocin

Oxytocin is nine amino acids long, and the US definition of a protein for biological-product purposes requires a defined sequence greater than 40 amino acids. Oxytocin falls outside that definition, and the consequence is measurable rather than theoretical: it is the only compound in this group that did NOT transition to a licensed biologic on 23 March 2020, and it is absent from the transition list on which every chorionic gonadotropin and menotropins application appears. It is also the only one made entirely by chemical synthesis, with a stated empirical formula and molecular weight, and the only one whose label warns of intrinsic pressor and antidiuretic properties arising from its structural similarity to vasopressin, which differs from it at only two positions.

Sources

1. US FDA. PITOCIN (oxytocin injection, USP) Synthetic, approved label, NDA 018261
2. US FDA. List of approved NDAs for biological products deemed to be BLAs on 23 March 2020, in which oxytocin does not appear
3. European Medicines Agency. Oxytocin, list of nationally authorised medicinal products, EMA/266096/2018
4. US FDA. Deemed to be a license provision of the BPCI Act
5. World Anti-Doping Agency. 2026 Prohibited List, in which oxytocin does not appear

This page describes a compound as a material and summarises published research about it. It is for general and procurement information only. It is not medical advice, not a treatment recommendation, and not guidance on use. Supplied for laboratory and research use, not for human consumption.