Half-life biological of oxytocin:

Oxytocin is a nanopeptide synthesised by supraoptic and paraventricular nuclei of hypothalamus. It is rapidly metabolised and degraded by oxytocinase and hence has a half life of 3 - 4 minutes and a duration of action of approximately 20 minutes. (DC Sutta TB of obstetrics 8th edtn pg 573)