Pharmacokinetic and toxicological aspects of the medication of beef-type calves with an oral formulation of chloramphenicol palmitate.

Chloramphenicol (CAP) plasma levels were determined after oral administration of four doses of CAP palmitate (each dose corresponding to CAP 25 mg/kg/12 h) to four ruminating beef-type calves. Steady-state plasma concentrations of CAP were reached after the fourth oral dose and varied between 5 and 6 micrograms/ml. Half-life of elimination of CAP was 4.5 h. In addition to CAP, dehydrochloramphenicol (DH-CAP), a metabolite of chloramphenicol, was detected in plasma at concentrations between 3 and 7 ng/ml. DH-CAP is known to be produced from CAP by intestinal bacteria. This is significant since DH-CAP is suspected of being involved in the development of fatal aplastic anaemia, which occurs in man after exposure to CAP. Thus, it cannot be excluded that DH-CAP residues may occur in edible tissues. A risk arising from DH-CAP can neither be excluded for the animals being treated with CAP nor for consumers.