PLASMA ELIMINATION AND URINARY-EXCRETION OF PROCAINE AFTER ADMINISTRATION OF DIFFERENT PRODUCTS TO STANDARD-BRED MARES

Plasma and urinary concentrations of procaine were examined in Standar dbred mares after subcutaneous administration of various doses (80 mg to 1600 mg) of procaine hydrochloride. Regardless of dose, peak plasma procaine values occurred within 1 h, but remained detectable in a dos e-dependent manner, with procaine present at 1 h with the 80 mg dose a nd 6 h at the 1600 mg dose. Similarly, peak urinary procaine concentra tions were attained within 1.5 to 3 h, irrespective of dose, while det ection time was dose-dependent, being 23 h for 80-200 mg doses but as long as 30-54 h with the 1600 mg dose. When mares were given a single intramuscular injection of a penicillin G-procaine preparation (Ethaci llin, Cillimycin, Penamycin, Derapen A, Azimycin or Diathal), peak pla sma procaine concentrations varied and were reached from 10 min to 3 h in all cases, with detection from 3 to 20 h after drug administration . Although the peak urinary levels of procaine occurred between 30 min s and 6 h, detection in urine in most cases was as long as 78-120 h ex cept for Diathal for which detection was limited to 54 h. Daily admini stration of a penicillin G-procaine preparation (Pen-Di-Strep) for 5 d ays produced a biphasic peak in plasma procaine at 3 and at 6-9 h with detection from 16 to 23 h after drug treatment. Although peak urinary procaine values were reached at similar times after single or multipl e injections, the duration of detection was markedly longer (425 h) af ter the multiple-dose regimen. Plasma procaine concentrations could no t be detected after topical (Special Formula 17900) or oral (Pro-Pen F eed Mix) penicillin G-procaine administration but procaine was detecte d in urine at 30 h with the topical and at 54 h with the oral treatmen t.