Techniques for plasma protein binding of demethylchlorimipramine

Clin Pharmacol Ther. 1979 Aug;26(2):265-71. doi: 10.1002/cpt1979262265.


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.

Publication types

  • Comparative Study

MeSH terms

  • Blood Proteins / metabolism*
  • Clomipramine / analogs & derivatives
  • Clomipramine / blood
  • Clomipramine / cerebrospinal fluid
  • Clomipramine / metabolism*
  • Clomipramine / therapeutic use
  • Compulsive Personality Disorder / drug therapy
  • Depression / drug therapy
  • Dialysis
  • Dibenzazepines / metabolism*
  • Gas Chromatography-Mass Spectrometry
  • Humans
  • Protein Binding*
  • Ultrafiltration


  • Blood Proteins
  • Dibenzazepines
  • Clomipramine