Pharmacotherapeutic group: anti-inflammatory, NSAID, aryl proprionic acids. ATCvet code: QM01AE91
Carprofen is a non-steroidal anti-inflammatory drug (NSAID), of the 2-aryl propionic acid class and possesses anti-inflammatory, analgesic and antipyretic activities. The mechanism of action of carprofen, is not well known. However, it was shown that the inhibition of the cyclo-oxygenase enzyme by carprofen is relatively weak at the recommended dosage. Moreover, it was shown that carprofen doesn’t inhibit the generation of thromboxane (TX) B2 in dog clotting blood and neither prostaglandin (PG) E2 nor 12-hydroxyeicosatetraenoic acid (HETE) in inflammatory exudate are inhibited. This suggests the mechanism of action of carprofen is not the inhibition of the eicosanoids. Some authors suggested an activity of carprofen on one or numerous inflammatory mediators not yet identified but no clinical evidence could be shown. Carprofen exists in two enantiomeric forms, R(-)-carprofen and S(+)-carprofen and the racemic form is the one marketed. Laboratory animal studies suggest that the S(+) enantiomer possesses greater anti-inflammatory potency. Ulcerogenic potential of carprofen has been shown in the rodents but not in the dogs.
After a single oral administration of 4 mg of carprofen per kg of bodyweight in dog, the time to obtain a maximum plasmatic concentration of 23 µg/ml is about 2 hours. The oral bioavailability is more than 90% of the total dose. Carprofen is more than 98% bound to plasma proteins and its volume of distribution is low. Carprofen is excreted in the bile with 70% of an intra-venous dose of carprofen being eliminated in the faeces, mainly as the glucuronide conjugate. Carprofen undergoes an enantioselective enterohepatic cycle in dog, with only the S(+) enantiomer being significantly recycled. The plasmatic clearance of the S(+) carprofen is about twice that of the R(-) carprofen. The biliary clearance of S(+) carprofen seems to be subject to stereoselectivity too as it is about three times higher than that of R(-) carprofen.