Procaine in the urine of racing Greyhounds: possible sources

Greyhounds (n = 25) were given procaine in the form of procaine HCl or procaine penicillin G or were fed meat prepared from a heifer given procaine penicillin G on 3 consecutive days before slaughter. Dogs given procaine HCl or procaine penicillin G were given daily doses equivalent to 9 mg of procaine/kg. Urine samples were collected from the dogs twice daily before dosing, during the dosing period, and for 4 days after final dose administration. All dogs excreted detectable concentrations of procaine in the urine, regardless of the dose form or route of administration. Blood plasma samples were prepared from 10 Greyhounds to determine procaine esterase activity. Hydrolysis of procaine by plasma esterases did not occur. Low plasma procaine esterase activity, coupled with rapid oral absorption of procaine, resulted in high urinary concentrations of the parent drug in dogs given procaine HCl or procaine penicillin G (9 mg/kg). Even in the dogs given relatively small doses (0.85 mg/kg) of procaine in the form of meat residues, urinary procaine concentrations were found. The results of these studies indicate that procaine is rapidly absorbed following oral administration and that meat from livestock given procaine penicillin before slaughter may serve as a source of urinary procaine in Greyhounds consuming the meat.