Pharmacology: Vaptans and Prostaglandins Flashcards
describe the action of ‘vaptans’
they act as competitive antagonists of vasopressin receptors
what are the different subtypes of ‘vaptans’
V1A, V1B and V2
describe the role of V1A receptors
they mediate vasoconstriction
describe the role of V2 receptors
they mediate water reabsorption in collecting tubule by directing AQP-2
describe the effect of V2 vaptans
blockade of V2 receptors causes excretion of water without accompanying Na, thus raises plasma Na conc.
give an example of a vaptan that is both a V1A and V2 antagonist
conivaptan
give an example of a V2 antagonist vaptan
tolvaptan
when is tolvaptan used
to treat the hyponatraemia in SIADH
what enzymes form prostaglandins
COX1 and 2
what are the major prostaglandins synthesised by the kidneys
PGE2 and PGI2
what are prostaglandins synthesised in response to
to ischaemia, mechanical trauma, angiotensin II, ADH and bradykinin
under what conditions do prostaglandins gain importance
in vasoconstriction, or decreased effective arterial blood volume, where they cause compensatory vasodilation
describe the ways by which prostaglandins affect GFR
direct vasodilation of afferent arteriole, also release renin leading to increased angiotensin II which vasoconstricts efferent arteriole
(results in increased filtration pressure)
describe why NSAIDs can negatively impact GFR
they inhibit COX, and so may precipitate acute renal failure where renal blood flow is dependant on prostaglandins
