- •Acetaminophen, propofol, carprofen, and aspirin are eliminated more slowly in cats, and are all metabolized by conjugation.
- •Cats lack uridine diphosphate glucuronosyltransferase (UGT) 1A6 and UGT1A9, which glucuronidate acetaminophen and propofol, respectively.
- •Slower aspirin clearance results mainly from deficient glycine conjugation and not deficient glucuronidation.
- •Cats lack N-acetyltransferase 2, which may be the reason they are prone to developing methemoglobinemia rather than hepatotoxicity from acetaminophen.
- •Cats have low thiopurine methyltransferase activity, which causes sensitivity to azathioprine toxicity.
- •Piroxicam is eliminated more quickly in cats than in humans and dogs, but the reason for this is unknown.
Drug pharmacokinetic differences between cats, dogs, and humans
- •All of the drugs that are eliminated more slowly in cats (ie, aspirin, propofol, acetaminophen, and carprofen) are cleared by metabolic conjugation, including glucuronidation, sulfation, and/or glycination.
- •Piroxicam, which is metabolized mainly by oxidation, is eliminated more rapidly in cats compared with dogs and humans (ie, the opposite of the conjugated drugs).
- •Elimination half-life values were highly correlated between dogs and cats for the nonmetabolized drugs, and poorly correlated for the metabolized (oxidized and/or conjugated) drugs.
- •Human elimination half-life data were poorly predictive of dog and cat elimination half-life data for most of the drugs evaluated.
|Drug||Species||Half-life (h)||CL (mL/min/kg)||Vd (L/kg)|
Acetylsalicylic Acid (Aspirin) and Salicylates
Molecular basis for differences in cats versus other species
Drugs with Evidence for Poor Glucuronidation in Cats
Drugs glucuronidated slowly in cats
Drugs glucuronidated efficiently in cats
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Disclosures: This work was supported by funds provided by the William R. Jones Endowed Chair in Veterinary Medicine at Washington State University. There are no conflicts of interest to report.