The influence of diuretics on the excretion and metabolism of doping agents - I. Mephentermine

The urinary excretion of mephentermine and its major metabolite phentermine in human volunteers was followed over a period of several days after oral administration of mephentermine. The excretion of both substances was affected by urinary pH. Maximum excretion was observed 2-4 h after administration and the total proportion of mephentermine excreted during 54 h was 57 to 83%. Based on urinary values, the biological half-life of elimination of mephentermine was 9.9 +/- 2.6 h. The ingestion of acetazolamide shortly after administration of mephentermine resulted in a decrease in excretion of both mephentermine and phentermine during one day; in some instances, the amounts of these substances in the urine were below the detection limit for a period of 3-9 h. The administration of frusemide only produced a urinary diluting effect during 2-4 h after administration.