Techniques for plasma protein binding of demethylchlorimipramine.
The cerebrospinal fluid (CSF) and plasma levels of demethylchlorimipramine (DMCI) were determined during treatment of depression or obsessive-compulsive disorders with chlorimipramine. In 18 patients the mean CSF/plasma ratio of DMCI was 2.6% +/- 0.7 SD with fourfold variation (1.1% to 4.0%). In spite of this variation, the levels in CSF and plasma at steady state correlated closely (r = 0.91; p less than  0.001). With equilibrium dialysis for the determination of the protein binding of DMCI, a much higher free fraction was found in patients (8.0 +/- 1.6%) and in control subjects (8.2 +/- 1.4%). It was shown that part of the plasma binding capacity was lost during the incubation. Results obtained by ultrafiltration (3.9 +/- 1.0% unbound drug) were closer to the in vivo results, but this method also had disadvantages; much of the drug was absorbed on the ultrafiltration dialysis membrane. Our results suggest that there is a need for care in the selection of a technique for studies of drug protein binding.
D001798:Blood Proteins / Q000378:metabolism*; D002997:Clomipramine / Q000031:analogs & derivatives / Q000097:blood / Q000134:cerebrospinal fluid / Q000378:metabolism* / Q000627:therapeutic use; D003193:Compulsive Personality Disorder / Q000188:drug therapy; D003863:Depression / Q000188:drug therapy; D003956:Dialysis; D003984:Dibenzazepines / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D011485:Protein Binding; D014462:Ultrafiltration
D001798:Blood Proteins; D003984:Dibenzazepines; D002997:Clomipramine