Toxciology Brief: Ibuprofen toxicosis in dogs, cats, and ferrets - Veterinary Medicine
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Toxciology Brief: Ibuprofen toxicosis in dogs, cats, and ferrets


VETERINARY MEDICINE




A nonsteroidal anti-inflammatory drug (NSAID) derived from propionic acid, ibuprofen has analgesic, anti-inflammatory, and antipyretic effects. It is commonly used in humans for short-term management of pain and fever and for long-term control of arthritic pain. It comes in various strengths. For over-the-counter use, it is available in 50- and 100-mg capsules or tablets (often chewable) and 20 and 40-mg/ml liquids for children, and in 200-mg tablets and capsules for adults. Prescription-strength tablets are 400, 600, and 800 mg. Ibuprofen also can be found combined with other medications such as pseudoephedrine hydrochloride or hydrocodone bitartrate. Common brand names of ibuprofen preparations include Advil (Wyeth), Midol (Bayer HealthCare), and Motrin (McNeil Consumer), although ibuprofen also is available in many generic formulations.1

In humans, ibuprofen taken at standard dosages appears to have a wide margin of safety. In general, there are fewer side effects than with similarly dosed aspirin.1 However, in dogs, cats, and ferrets, ibuprofen has a narrow margin of safety and is a frequent toxicosis reported to the ASPCA Animal Poison Control Center (APCC). In one review of ASPCA APCC data on calls reporting generic drug exposures in dogs and cats, ibuprofen was the most common drug involved.2 Dogs were the animals most commonly poisoned by ibuprofen, and most exposures were acute—usually the result of ingestion of numerous tablets after a dog chewed open a bottle (ASPCA APCC Database: Unpublished data, 2001–2003). Some ibuprofen formulations have a sweet coating and are readily eaten by dogs. In some cases, ibuprofen was administered to pets in the mistaken belief that it was safer than aspirin (ASPCA APCC Database: Unpublished data, 2001–2003).

Mechanism of action

While the exact mechanism of ibuprofen's action is not fully understood, it is generally thought that ibuprofen inhibits the conversion of arachidonic acid into various prostaglandins by reversibly blocking the actions of cyclooxygenase (COX) enzymes. By inhibiting COX-2 enzymes, ibuprofen reduces the production of inflammatory mediators such as prostaglandin E2 (PGE2) and prostaglandin F (PGF).3 However, ibuprofen also inhibits COX-1 enzymes, which can reduce the production of substances necessary for maintaining the normal gastric mucosal barriers, renal blood flow, and platelet aggregation.1

Pharmacokinetics

About 80% of ibuprofen is absorbed when taken orally in humans1; in dogs, 60% to 86% of the dose is absorbed.4 In humans, the time to reach peak plasma concentrations varies from 47 to 120 minutes, depending on the formulation. Liquid forms reach peak concentrations soonest, chewables next, and tablets last. Ingesting ibuprofen with food decreases the peak plasma concentration and increases the time to reach it.1

Ibuprofen is highly protein-bound (90% to 99%).1 Elimination is through hepatic biotransformation to inactive metabolites excreted by kidney filtration and secretion. About 70% of the drug is excreted in the urine as metabolites or unchanged drug; the rest is lost through feces. Marked enterohepatic recirculation occurs.5 In dogs, the elimination half-life is 3.9 to 5.3 hours.4


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Source: VETERINARY MEDICINE,
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