NSAIDs Smallies Flashcards
(47 cards)
OUtlie 3 main arachidonic acid pathways LOOK UP
COX 1 physiological
How can COX2 selective drugs be made?
Phyiscal shape and size of molecule
When is COX2 activated and released?
- tissue damage
- bacterial LPS
- cytokines
- growth facos
- PGEs predominant eicosanoid -> inflam
- tumout s
COX2 inhibition clinical benefits?
> suppprression of - inflam - pain - fever > alzheimers > tumours - coon, pancreas, lung, TCC (bladder), melanoma
How are NSAIDs classfied?
> non-selective > preferential - >2x (usually 10-40x) greater inhibition of COX2 > selective - 100x selective
What do coritcosteroids inhibit?
- immune system
- phosphlipase a (cell membrane phosphlipid -> arachidonic acid)
Other than COX
- 5LO inhibition
- PG recepto blockade
- scavengin free adical s
- anti-bradykinin properites
- ihibition enzyme rlease or action
- inhibiton cytokine release
- inhibition NFkB
How are COX1/COX2 inhibition potency data expressed? Gold standard data??
IC50
(wide inter and intra laboratory variation in data)
- beware studies done on cell culture/rodents/tumour cell lines etc.
> GOLD STANDARD: wholeblood assay in species of interest
How are COW assays assessed?
Methods
> COX1 inhibition
- clot induced thromboxane B2 production inhibition
> COX 2 activity
- inhibition of LPS induced PGE2 production
What factors affect toxicity profiles of NSAIDs?
- paritially COX1:COX2 ratio
- degreee of acidity of pro-drug (direct gastric mucosal dmage)
- plasma t1/2
- degreee of enterohepatic recycling (^ in dogs c. humans)
Therapeutic aim of NSAIDs?
- > ## 80% inhibition of COX2 for as much of 24 hr period a sposs
Which drugs are non-selective COX1/2?
- aspirin
- phenylbutazone
- ketoprofen
- tolfenamic acid
What are preferential COX 2 inhibitiors?
- 2-40x more selective
- at higher end of dose range will affect COX1
- analgesic and anti-inflam activity thati nhibits COX2
- include “coxibs” (initially thought to be elective)
Which drugs are preferentially COX2 blockers?
- meloxicam
- carprofen
- mavacoxib
- cimicoxib (probs, data not published)
- deracoxib (US)
How may COX2 selecctivity in preferential drugs be affeected by dose?
Different shaped curves
- inhibition of COX1 when COX2 inhibited by 80% = ~25% carprofen and meloxicam
- inhibition of COX1 when COX2 inhibited by 100% = ~60% carprofen, ~70% meloxicam
What is a true specific COX2 inhibitor?
more than 100x selective for COX2 , no COX1
What drugs are COX2 selective (coxibs)?
- firocoxib
- robenocoxib
> no generic as still under patent (yet!)
Which drug is a dual inibitor (COX nd LOX)?
> tepoxalin
- inhibit LOX for short period during day
- non-selectie COx1 ad COX2
Which human NSAIDs are bad for pets?
- naproxen
- ibuprofen
- piroxicam (only for TCC)
- mefanamic acid
- diclofenac
- paracetamol (acetaminophen) only in cats (ok in dogs)
What does paracetamol cause in cats?
- face and feet oedema
- methaegloinaemia (brown blood)
How does carprofen action differ in cats adn dogs? Horses? Man?
- both COX2 selective
- much longer half life in cat, so daily doses -> GI disaster
- horse non-selective
- man COX1 preferentail
Pharmacokinetics of NSAIDs ? carprofen? Not sure which supposed to be
- well absorbed from stomach and SI
- well absorbed sc or im injection
- topical administration -> drug levels in tissues adn synovial fluids comparable to oral administration
- oromucosal delivery can acheive effective systemic levles eg. Revitacam (rotanacoxib??)
- weak acids so readily penetrae inflamed tissue
- highly protein bound (accumulation of drug in protein rich inflam exudate)
- duration of effect of NAIDs may exceed apparent systemic t1/2
How are NASIDs metabolised? how does this differ between individuals?
> excreted at varying rates
- depending on metabolic pathway and extent of enterohepatic circulation
elimnation T1/2 varies w/ drugs and species
toxicity and pharmacokinetic data on NSAIDs in one species EVER TRANSPOSED TO ANOTHER
How does cats ability to metabolise aspirin differ to dogs? clinical implications?
- prolonged t1/2 in cats
- same dose but q72hrs not BID