following the topical application of four times the recommended daily dose of copper phenylbutazone to the horse for 5 days , minor skin irritation occurred and trace concentrations of phenylbutazone ( maximum 0.6 microgram/ml ) and negligible concentrations of oxyphenbutazone and gamma-hydroxyphenylbutazone were detected in the plasma .
C0031463
phenylbutazone
C0030078
oxyphenbutazone