[The stereoselective binding of praziquantel enantiomers to plasma proteins]

The stereoselective binding of praziquantel (PQT) enantiomers to plasma proteins was studied by equilibrium dialysis. The binding of (+/-)-PQT and its enantiomers to bovine serum albumin (BSA) and rabbit plasma was unsaturable when initial drug concentrations from 1 to 32 mumol/L were used. The binding capacity (nK) of (+/-)-PQT to BSA (1.47 or 5.88 x 10(-4) mol/L) was greater than that of (-)-PQT with a (+)-/(-)-PQT ratio of 1.25 or 1.26, respectively. However, the preferential binding of (-)-PQT to rabbit plasma was found to be 73.7 +/- 4.4% for (-)-isomer and 58.3 +/- 10.1% for (+)-isomer (n = 8, P less than 0.05). The binding of (+)- and (-)-PQT to human plasma was 81.9 +/- 4.2% and 83.2 +/- 6.9% (n = 10, P greater than 0.05) respectively, which seems to be not stereoselective. These results indicate that there are species differences in the stereoselective binding of PQT enantiomers to plasma proteins.