Production of antisera to phenylbutazone and oxyphenylbutazone for use in immunochemical detection assays

Abstract

Phenylbutazone, a non-steroidal anti-inflammatory drug commonly used to treat horses for musculoskeletal disorders, can cause adverse effects in humans and is therefore not permitted for use in food-producing animals in the EU. In recent years some equine and bovine samples have been found to be non-compliant. While physicochemical methods of analysis exist there is a need for lessexpensive, rapid screening methods such as immunoassays. This study describes the production of antisera to detect phenylbutazone and its main metabolite, oxyphenylbutazone. Four haptens were chosen for immunogen preparation and two of these, suxibuzone and γ-hydroxyphenylbutazone, produced antisera with 50% of maximal inhibitory concentration (IC 50 s) of <5 ng mL −1 for phenylbutazone. Antisera with IC 50 s of 5.5 ng mL −1 for phenylbutazone and 5.6 ng mL −1 for oxyphenylbutazone were produced by their respective haptens. The figures suggest that the antisera could deliver detection capabilities below the concentration that is recommended by the Community Reference Laboratory (5 ng mL −1 ).