NSAIDs - pharmacology and relevance to clinical practice Flashcards
mechanism of effect
decrinflbyinhibitingproduction ofprostaglandinsreleasedbydamagedtissuethroughinhibitionofcyclo‐oxygenaseenzymes (COX)
clinicalindications
Controlpain+ inflinnoninfectious/nonallergic infldisorders
decr plateletaggregation
Ophthalmology
Managementofsomeimmunologicaldiseases
managementofendotoxicshock
in which diseases is a decr in plateletaggregation needed
Thromboembolus
Heartwormdisease
use in ophthalmology
Rxofkeratitisandscleritis
donotinhibitre-epithelializationofthecornea
intraocularsurgery
use in managementofsomeimmunologicaldiseases
SLEandrheumatoidarthritis
Anti‐infl
MaystimulateT‐suppressorcellsagainstT‐helpercells+auto‐antibody‐producingBcells
COX‐1 - function
Produceprostaglandinsimportantinthephysiologicalmodulationoffunction
COX‐2 - when is it activatedandreleased
tissuedamage bacteriallipopolysaccharide cytokines growthfactors inflwherePGE2ispredominanteicosanoid
COX‐2 inhibition ‐ clinicalbenefits
suppression of infl, pain + fever
COX‐2inhibition - cancers that can be treated
colon pancreas lung transitionalcellcarcinoma melanoma
best Cyclo‐oxygenase‐assaymethod
whole blood assay
Cyclo‐oxygenase‐assay - COX-1
Inhibitionofclot‐inducedthromboxaneB2 production
Cyclo‐oxygenase‐assay - COX-2
Inhibitionoflipopolysaccharide(LPS) ‐ inducedprostaglandinE2 (PGE2)production
COX‐1:COX‐2 ratio
Varieswithdifferentdrugs
differenttoxicityprofiles
OtherfactorsmayinfluencedegreeofsafetyofNSAIDs
NonselectiveCOXinhibitors
Aspirin
Phenylbutazone
Ketoprofen
Tolfenamicacid
PreferentialCOX‐2inhibitor
2to40‐foldmoreselectiveforCOX-2
Analgesic+anti‐inflactivityatdosesthatinhibitCOX‐2butnotCOX‐1
SomeCOX‐1inhibitionpossibleatelevated/therapeuticdosages
PreferentialinhibitorsofCOX‐2
Meloxicam
Carprofen
Mavacoxib
Cimicoxib
selectiveinhibitorsofCOX‐2
Firocoxib
Robenocoxib
Dualinhibitor
Tepoxalin
Speciesdifferences
Potency
RelativeselectiveforCOX‐1andCOX‐2
Carprofen - dog
COX‐2preferential
Carprofen - cat
Butsignificantlylongerhalflifethandog
Dailydosing= GIdisaster
Carprofen - horse
non-selective
pharmacokinetics
Wellabsorbedfromstomach+smallintestine
Wellabsorbedaftersubcutaneous/intramuscularinjection
Oromucosaldeliverycanachieveeffectivesystemiclevels
readilypenetrateinflammedtissue
Highlyproteinbound
metabolism
excretedatvaryingrates-dependsonmetabolicpathway+
extentofenterohepaticcirculation
Eliminationhalf‐lifevariesconsiderablybetweendrugs+species
differs across species
Potentialadverseeffects
GI
Renal
Haematological
PGEandPGI2 protectthegastricmucosaby…
inhibitinggastricacidsecretion
maintainingmucosalbloodflow
beinginvolvedinsecretion+compositionofhealthymucous
intercellularmessengersforthestimulusofmucosalcellturnover+migration
mainmechanismbywhichGIulcerationoccurs
inhibition of COX-1
gut cells expressing COX-2
macrophages
neutrophils
myofibroblasts
endothelial cells
CanCOX‐2inhibitionretardulcerhealing?
possibly
COX-2 in the gut
rapidlyexpressedinresponsetoGIinjuryandcontributessignificantlytomucosaldefenseandrepair
use of COX-2 inhibitors during infl
safety in presence of infl needs to be shown
shouldn’t be used during infl
Otherfactorsthatinducegastrointestinaldamage
relativerateofgastricabsorption
systemicavailabilityofthedrugviathecirculationtothemucosa
directdamagetogastricmucosa
degreeofenterohepaticre‐cycling
Ulcerogenicpotentialincreasedby…
concurrentcorticosteroids
dehydration
hypovolaemicshock
disruptiontonormalgutbloodflow
Prostaglandinsandrenalfunction
Whenrenalperfusionreduced,renalprostaglandinsmaintainrenalbloodflowviatheirvasodilatoryactions
significant renal toxicity if…
volume‐depleted
avidlyretainingsodium
pre‐existingrenalinsufficiency
Haematopoieticeffects - Thromboxane
potentvasoconstrictor+ activatorofplateletaggregation
Inhibitionofthromboxanecanleadtoincr riskofbleeding
NSAIDsandtheliver
NSAIDsundergoextensivehepaticmetabolism
Carewithhepaticdisease