PHARMACOKINETIC STUDY OF DIPYRONE METABOLITE 4-MAA IN THE HORSE AND POSSIBLE IMPLICATIONS FOR DOPING CONTROL

The pharmacokinetic behaviour of dipyrone metabolite 4-MAA in serum wa s determined in seven horses of different breeds after a single intrav enous dose administration. A biexponential formula was fitted to the s erum concentration vs. time data. The median half-life of the eliminat ion phase (t(1/2 beta)) was 4.85 h (range 5.04 h), the median volume o f distribution (Vd(area)) was 1.85 L/kg (range 3.2 L/kg) and median of total clearance was 4.0 mL/min/kg (range 2.3 mL/min/kg).