Residues of clenbuterol in the eyes of therapeutically treated veal calves

Six Brown Swiss veal calves were medicated with the therapeutic dose of the β‐adrenoceptor agonist clenbuterol (0.8 μg kg‐1 body weight, orally, twice daily for 10 days). After the prescribed withdrawal period of 28 days, the calves were slaughtered and the eyes were analyzed for clenbuterol residues. The residues varied in concentration from 2 to 5 ng clenbuterol g‐1 eye tissue. Based on these data, a variation range (< 6.5 ng g‐1), a threshold range (6.5–9.7 ng g‐1) and an elevated range indicating misuse (> 9.7 ng g‐1) could be calculated, providing guidelines for handling such animals. There was parallelism (r = 0.73) between the plasma clenbuterol concentration during treatment and residues found in the eyes after withdrawal, indicating passive accumulation.