Ans. a (5 per 10 minutes) (Ref. Williams Obstetrics 22nd/Ch. 22)Oxytocin is a nanopeptide, synthesized in hypothalamus (Paraventricular nucleus) but stored and released by posterior pituitary. Its half life of 3-4 minutes. Alcohol inhibits its release. Uses: Stimulates labor, uterine contractions, milk let-down; controls uterine hemorrhage. Oxytocin when used for stimulation of labour should be discontinued if the number of contractions persists with a frequency > 5 in a 10-min period or 7 in a 15-min period or with a persistent nonreassuring FHR pattern.INTRAVENOUS OXYTOCIN ADMINISTRATION for stimulation of labour# The goal of induction or augmentation is to effect uterine activity sufficiently to produce cervical change and fetal descent while avoiding development of a nonreassuring fetal status.# Discontinuation of oxytocin nearly always rapidly decreases the frequency of contractions.# When oxytocin is stopped, its concentration in plasma rapidly falls because the mean half-life is approximately 5 min.# It is found that a uterine response occurs within 3 to 5 minutes of beginning an oxytocin infusion and that a plasma steady state is reached in 40 minutes.# Response depends on -- preexisting uterine activity,- cervical status,- pregnancy duration, and- individual biological differences.# The uterine response to oxytocin increases from 20 to 30 weeks and increases rapidly at termEducational point:# Maximal Dosage of oxytocin- The maximal effective dose of oxytocin to achieve adequate contractions in all cases is not known.- Wen and colleagues found that the likelihood of progression to a vaginal delivery decreases at and beyond an oxytocin dosage of 36 mU/min.- At a dosage of 72 mU/min, however, half of the nulliparas were delivered vaginally.- Thus, if contractions are not adequate--less than 200 Montevideo units--and if the fetal status is reassuring andlabor has arrested, an oxytocin infusion dose greater than 48 mU/min has no apparent risks.Hypothalamic/pituitary drugs DRUGCLINICAL USE1.GHGH deficiency, Turner syndrome.2.Somatostatin (octreotide)Acromegaly, carcinoid, gastrinoma, glucagonoma, esophageal varices.3.OxytocinStimulates labor, uterine contractions, milk let-down; controls uterine hemorrhage.4.ADH (DDAVP)Pituitary (central, not nephrogenic) Dl.