Saq- Oxytocin

Q.Ou tli ne briefly t he ph ar ma co lo gy of o xyto ci n Overview •Oxytocin ---endogenous polypeptide hormone released from posterior pituitary---synthesis from paraventricular cellof hypothalamus •synthetic water soluble polypeptide of eight amino acid that used in obstetric parctice

Preparation •Also available in synthretic form •Syntocinon- synthetic oxytocin --Octapeptide used as synthetic preparation to cause uterine constriction •Prepared as syntocinon •Available in 5 u/ml or 10 u/ml Structures activity relationship •? Octapeptide ---or ? nonapeptide chemical compound • syntheticly prepared oxytocin synthesis • identical to ---natural hormone ---secreted from posterior pituitary • not secreted from posterior pituitary Formula structure

structure activity relationship • naturally occuring nona, octa peptide • comprised of S-S bond----imporatant for activity combination of compound • synthetic oxytocin---can be combine with ergot • ergot---alkaloid from fungus • combination of oxytocin and ergot---known as syntocinon Mechanism of action drug target

•smooth muscle cell receptor drug action bind to receptor •smooth muscle receptor activated----increase in permeability to K+ •effect –decerase membrane potential •increase excitability of uterine smooth muscle •effect coordinated , regular uterine •Action on gravid uterus and breast milk duct Clinical use Augmentation of labour •Used in obstetric to cause uterine constriction •Uterine constriction ---as induction of labour Post-partum •Uterine contraction post-delivery •Also to prevent PPH Lactation •To induce lactation

Dose and administration • Onset – 30 sec- 1 minutes – IV, 2 minutes - Im • Duration of action – 3-5 minutes IV, IM – 60 minutes Pharmacokinetic Absorbtion •Poor oral bioavailibility •Reason; inactivation by chymotripsin as a first pass effect •Has to be administered parentally •Also can be given, intranasal Pharmacodynamic CVS HR •Tachycardia ---then hypotension ---non-specific ST changes SVR •Causes vasodilation ---manifestated as flushing •Vasodilation ---decrease SVR---hypotension BP •Hypotension ----initiate baroceptor reflex •Baroreceptor reflex ---reflex tachycardia---net increase in cardiac output •Anesthetic implication ---further aggravate hypotension produced by concurrent anesthetic agent

Other •Has very little antiduretic action •But may cause water intoxication after prolonged infusion particularly if given with 50% dextrose Drugs interaction Suxamethonium •Antagozed effect of sux Blood transfusion •Inactivated with blood transfusion Contraindication Adverse effect Placental blood flow Foetal well being HEMABATE Why do you use oxytocin but not ergometrine for induction of labour Where does ergot come from? Fungus