Oxytocin determination by radioimmunoassay.

A sensitive and specific radioimmunoassay method was developed for the determination of oxytocin in human serum. Serum oxytocin levels were assayed in five healthy male volunteers and four healthy non pregnant female volunteers after rapid intravenous injection of 2 U synthetic oxytocin. Peak oxytocin levels were found at 30 s after intravenous administration. The half-life (T1/2) of oxytocin was 6 min 22 s in male and 6 min 53 s in female serum.