A review of objective assessments of orthopaedic analgesic efficacy of non-steroidal anti-inflammatory drugs in horses

Abstract

There are a limited number of published objective assessments of the orthopaedic efficacy of various non-steroidal anti-inflammatory drugs (NSAIDs) in horses. Several different models of pain in horses have been used, but the least invasive orthopaedic model is the reversible foot lameness model using a shoe with either a mechanical heart bar or an eccentrically-placed threaded nut accommodating a bolt, with both models allowing variable levels of lameness after tightening of the bar or bolt against the solar surface of the foot. These and other models have yielded objective data, reviewed here, on NSAID efficacy in orthopaedic conditions. Phenylbutazone and flunixin are of comparable efficacy, and each is superior to ketoprofen, in the reversible model of foot pain, evidenced at rest, during treadmill exercise, and during recovery after exercise. The selective cyclooxygenase (COX)-2 inhibitor firocoxib, given either orally or intravenously, appears to be an effective alternative to traditional pan-COX-inhibiting NSAIDs, but an initial three-fold loading dose is necessary with intravenous firocoxib to achieve steady state and full efficacy faster than the label dose allows. Meloxicam has also been shown to be effective in two published orthopaedic studies. Acetaminophen/paracetamol has shown some initial promise in preliminary studies using the reversible model of foot pain. Combination therapy should involve appropriately-dosed NSAIDs with differing onsets and durations, whereas drugs with similar onsets and durations may not be synergistic. Sanctioning bodies and local or federal laws may restrict or prohibit the use of NSAIDs before or during equestrian competition.