Excretion of levamisole in milk from cows treated with various formulations.

The rate of disappearance of levamisole in milk from cows given levamisole hydrochloride drench, levamisole resinate in feed pellets, levamisole hydrochloride boluses, or levamisole phosphate injectable was determined. Each formulation was given as a single treatment to each of five cows at a rate equivalent to 8 mg of levamisole hydrochloride/kg of body weight. Levamisole hydrochloride residues in milk averaged .50, .55, .58, and .32 ppm at 12 hr after the administration of levamisole drench, feed, bolus, and injectable formulations. Levamisole hydrochloride residues were below .01 ppm in milk at 48 h after drench treatment and at 60 h after treatment with other three formulations. Toxicity symptoms were not observed in any cows following treatment.