is the treatment of acute laminitis in horses. Laminitis is treated initially with injectable phenylbutazone at dosages up to 8.8 mg/kg, followed by therapy PO at 2.2-4.4 mg/kg, bid. Because the therapeutic index for phenylbutazone is relatively narrow, the dosage should be adjusted to the minimum possible to maintain comfort and avoid toxicity. Gl effects (eg, anorexia) and depression are the most frequent adverse effects associated with phenylbutazone. Ulcers may occur in the mouth, stomach, cecum, and the right dorsal colon. The ulcerogenic potential of phenylbutazone in horses is greater than that of flunixin meglumine and ketoprofen. Phenylbutazone dosages of 3-7 mg/kg, PO, tid, are recommended in dogs. In dogs, phenylbutazone has been associated with bleeding dyscrasias, hepatopathies, nephropathies, and rare cases of irreversible bone marrow suppression.