NSAIDS PT 2 Flashcards
prostacyclin (PGI2) fx in vessels
stimulates vasodilation and inhibit platelet aggregation inhibit this promote clotting (high does aspirin will do this thats why can only give a low dose)
NSAID absorption
- absorbed rapidly and almost completely following oral administration - peak plasma concentration 2-4 hrs after oral administration - absorption mainly in stomach and upper small intestine, influenced by pH - most are weak acids and are un-ionized in highy acidic gastric environment in
NSAID un-ionized state
high lipid soluble and easily diffuse into gastric cells where pH is higher and the drug dissociates; NSAIDs highly protein bound (mainly to albumin) only unbound drug is biologically active
NSAID metabolism and excretion
metabolized in lier and mainly excreted in urine - eliminated by conduction (glucuronidation, sulfating, glycination), or oxidation (cytochrome p450 enzymes)
carporphen and keotprophen eliminated
primarily by conjucation
meloxicam and piroxiacm eliminted
clear by oxidation
feline NSAID elimination
cats defecting in several drug conjunction pathways -> slow elimination of certain drugs must be careful with dosing or can -> adverse effects - phenolic compounds slow elimination in felines bc lack several enzymes for glucuronidation - certain drugs, piroxicam cleared more rapidly in cats than humans and dogs - slower aspirin clearance bc poor glycine conjugation
adverse effets NSAIDs
common: - V+ - D+ - anorexia - lethargy - melena mostly due to gastropathies and renal toxicosis Uncommon: - cardiovascular and hepatic problems possible but rare
gastric epithelium normal
- gastric epithelium normally secretes bicarbonate-rich fluid and forms protective mucosal gel layer providing defense against gastric acid - gel contains phospholipids that make it hydophobic preventing back diffusion of acid from gastric lumen to epithelial cells - surface epithelial cells rapidly migrate and divide to repair small defects - Adequate mucosal blood flow allows epithelium to tolerate wide array insults, reduced mucosal blood flow -> sever mucosal injury
NSAIDs gastric damage
- induce gastric damage through local and systemic effects -NSAIDs slightly acidic can become concentrated in gastric mucosa via ion trapping -> direct cellular injury - inhibition endogenous PG production -> systemic effects bc decreased PG production -> decreased mucin quality and bicarbonate content of mucous gel layer -> more vulnerable mucosa more vulnerable to acid-induced injury - NSAIDs can inhibit endogenous prostanoids which have vasodilatory affect normally-> areas reduced blood flow w/ in mucosa
renal blood flow regulation normally
- PGE2 and PGI2 function normally function as vasodilatory agents to regulate renal blood flow, when there is decreased renal profusion PGs cause afferent arteriolar dilation -> maintain renal blood flow by counteracting the effect of systemic vasoconstrictors
shorter use NSAIDs healthy animal renal function
should have little effect on renal hemodynamics and function
Use of NSAIDs during hemodynamic compromise
circulating vasoconstrictors released to maintain vascular resistance and blood pressure at expense of organ blood flow, kidneys more dependent on vasodilatory effects of PG to maintain renal blood flow and glomerular filtration rate; use of NSAIDs during this time will prevent this retention of renal blood flow and glomerular filtration rate normally achieved during hemodynamic compromise which: can -> ischemic kidney injury -> acute renal failure
NSAID potential risks in cardiovascular and hepatic systems
- vet patients without cardiovascular or hepatic problems rarely present adverse symptoms in these symptoms with NSAIDS - NSAIDs can generate impabalcne between vasodilatory PGI2/PGE2 and vasoconstrictive TXA2 in endothelium which can -> thrombosis and heart failure - COX2 inhibition by NSAIDs promotes sodium and water retention -> exacerbation heart failure and hypertension and increase adverse ventricular remodeling - acute liver failure possible after prolonged usage or an overdose like any other drug