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The pharmacokinetic properties of sulphamerazine, following oral application of granulated Mebacid to cattle, calf, and sheep, were compared with results obtained from the use of Mebacid tablets. Elimination half-life was higher in cattle, calf, and sheep, following oral application of Mebacid tablets. Different pharmacokinetic properties of sulphamerazine were found to exist between the two modes of preparation. Sulphonamide was eliminated more rapidly by cattle, calf, and sheep, when granulated Mebacid was used. When granulate is used, higher sulphamerazine doses have to be applied to calf and sheep to obtain the sulphonamide levels required for effective therapy. No intolerance was recorded from the above species, following oral application of granulated Mebacid.

Pharmacokinetic data of sulphamerazine were recorded from eight heads each of calf, adult cattle, horse, and sheep, following intravenous application of Mebacid 200, and mathematical implications were discussed. Exponential excretion was recorded from all species, according to the following equation: c = B x e-k2 x t The most favourable pharmacokinetic parameters were recorded from calf.

The disposition of sulfamerazine after oral and after IV administrations was studied in lambs at different times after birth. There was a gradual increase in systemic clearance and plasma binding until the 9th week. After sulfamerazine was given orally, there was a marked evolution in the shape of the concentration-time curves in function of age, strongly suggesting a defective absorption rate in the first weeks after birth. For antipyrine, too, the clearance increased gradually during the period of study, but absorption seemed to be rapid in the very young animals.

Date from plasma and urine samples from four ewe lambs were analyzed after administration of sulfamerazine as single IV and oral doses. A two-compartment pharmacokinetic model was developed to describe the disposition of sulfamerazine. The drug was eliminated, primarily by renal excretion of (i) unchanged sulfamerazine and metabolism to an acetyl metabolite, (ii) polar conjugates, and (iii) a third metabolite. The biological half-life of the drug was 6.6 hours. The average value of the absorption rate constant was 0.433 hour-1 (half-life 1.60 hours). Sulfarmerazine was relatively completely absorbed (approx 81% of dose) after oral administration in solution.