Disposition of diminazene aceturate (Berenil) in trypanosome-infected pregnant and lactating cows.

Three cows were repeatedly infected with different strains of Trypanosoma congolense and treated intramuscularly each time with a different dose of diminazene aceturate (Berenil). Biphasic decline was observed of the maximal plasma drug levels, which were attained at 15 min after the first treatment and at 30 min after the second and third treatments. The rate constants for the distribution and terminal phases depended on the period of exposure to parasitaemia of the animal at the time of treatment. Maximal diminazene aceturate residue levels were found in milk 8 h post treatment and declined biexponentially to 4.56 ng ml-1 and 8.76 ng ml-1 at 21 days post treatment after 3.5 mg kg-1 and 7.0 mg kg-1 doses, respectively. In the three cows, higher drug residues were found in the kidney (7.04, 3.92 and 7.99 micrograms g-1) than in liver (3.26, 2.87 and 1.24 micrograms g-1) and heart (1.79, 1.25 and 1.03 micrograms g-1). The results of this study indicate that the level of parasitaemia (degree of anaemia) in the animal at the time of treatment affects the distribution, disposition and elimination of diminazene aceturate in the animal. Furthermore, the residue level in milk after treatment depends on the treatment dose and could easily be bioavailable to the consumer.