Determination of mitotane (o,p '-DDD) and its metabolites o,p '-DDA and o,p '-DDE in plasma by high-performance liquid chromatography

The adrenolytic agent mitotane (o,p'-DDD or I,1-(o,p'-dichlorodiphenyl)-2,2 -dichoroethane) is believed to be metabolically activated, resulting in the generation of reactive intermediates or the formation of o,p'-DDA. A new h igh-performance liquid chromatographic (HPLC) method for measurement of mit otane and two of its metabolites, o,p'-DDA (1,l-(o,p'-dichlorodiphenyl) ace tic acid) and o,p'-DDE (1,1-(o,p'-dichlorodiphenyl)-2,2 dichloroethene), in plasma has been developed. Sample preparation involves precipitation of pl asma proteins with acetone before chromatographic separation under isocrati c conditions on a silica-based diphenyl column. Mitotane and metabolites ar e quantified by ultraviolet detection at 218 nm. Recoveries for the three c ompounds range between 99% and 110%, with between-day and within-day coeffi cients of variation <6% within the therapeutic range. Limits of detection a re 0.5 mu M and the assay is linear up to at least 800 mu M for o,p'-DDA an d 100 mu M for mitotane and o,p'-DDE. The method has been evaluated using s amples from three patients on mitotane therapy, revealing o,p'-DDA levels i n plasma 3 to 10 times higher than the levels of the parent compound.