A large number of prescription and nonprescription NSAID are available for human use. However, due to species differences in metabolism, efficacy, and toxicity, many are not recommended for use in animals. For example, in dogs, indomethacin is highly toxic to the GI tract and may result in severe ulceration, hematemesis, and melena at therapeutic doses. Piroxicam undergoes extensive enterohepatic recycling in dogs, resulting in a prolonged plasma half-life. GI ulceration and bleeding and renal papillary necrosis have been observed in dogs receiving piroxicam dosages of 0.3-1 mg/kg, sid. Ibuprofen is an arylpropionic acid derivative that has been used in dogs as an anti-inflammatory agent. However, dogs are much more sensitive to the development of GI side effects from ibuprofen administration than are humans. At therapeutic doses, adverse effects observed in dogs include vomiting, diarrhea, GI bleeding, and renal infection. Ibuprofen is not recommended for use in dogs or cats. Naproxen has been used in horses at a dosage of 5-10 mg/kg, sid-bid. Bioavailability is lower (~50%) for naproxen than for other NSAID, and the elimination half-life is ~5 hr in horses. In dogs, the elimination half-life of naproxen is 35-74 hr, presumably due to extensive enterohepatic recirculation. The pharmacokinetics in dogs also appear to be breed dependent. Due to the prolonged half-life of naproxen, dogs are extremely sensitive to its toxic effects. |
Coxib class drugs, including rofecoxib, celecoxib, and valdecoxib, recently introduced in human medicine, are COX-2 selective. The drugs are widely prescribed in humans because they do not inhibit COX-1 at therapeutic dosages. In clinical studies, the incidence of GI ulceration in patients receiving valdecoxib or celecoxib was significantly less than that of those receiving naproxen. The use of these drugs in animals has yet to be fully investigated. One pharmacokinetic study with celecoxib in Beagles demonstrated variability in drug elimination between dogs. In that study, one subgroup of Beagles metabolized celecoxib much more rapidly than the other, with elimination half-lives of ~2 and 18 hr, respectively. Until further data are available regarding the pharmacokinetics and safety of these drugs in animals, their use in veterinary medicine is not recommended. |
| |