Posterior pituarty pharmacology Flashcards
What is oxytocin used for ?
Oxytocin is released at the end of labour to stimulate birth but, the uterus needs to be primed by local prostaglandin production before it works.
This happens within the 3rd trimester
What two medications does the posterior pituitary release
oxytocin and ADH
What medication be used for induction of labour ?
Dinoprostone
(PGE2)
Induction labour
What can be used for early therapuetic abortion ?
Misoprostol
(PGE1 analogue)
Early therapeutic abortion
What can be used to prevent premature labour ?
An oxytocin receptor antagonist, atosiban can be used to prevent premature labour, being more effective than smooth muscle relaxants used previously such as salbutamol.
Anti-diuretic hormone (ADH)
ADH release from the posterior pituitary controls the volume of urine excreted by the kidney through its V2 receptor in the collecting tubule. In higher doses ADH constricts blood vessels through its V1 receptor and is called vasopressin.
Vasopressin can be given as a nasal replacement spray in diabetes insipidus of central origin. However, if diabetes insipidus is of nephrogenic origin carbamazepine, an anti-epileptic drug which sensitizes the collecting tubule to ADH or a thiazide diuretic may be of help. At first site the use of a diuretic would seem counter-intuitive but thiazides inhibit the maximum ability of the kidney to dilute urine. Vasopressin is also used as a vasoconstrictor for example together with local anaesthetics. For the syndrome of inappropriate ADH secretion (SIADH) which produces hyponatremia, vomiting and confusion leading to cerebral oedema, a V2 ADH receptor antagonist , tolvaptan is potentially available.
How to treat Syndrome of Inappropriate ADH secretion (SIADH)
(HYPONATREMIA)
Problem is often too much water which dilutes sodium
hyponatremia (<134 mEq/l) headache, vomiting, confusion – if severe cerebral oedema
tolvaptan (V2 receptor antagonist)
demeclocyline (tetracycline)
