The rapid hydrolysis of chlordiazepoxide to demoxepam may affect the outcome of chronic osmotic minipump studies.
BACKGROUND
In chronic studies, the classical benzodiazepine chlordiazepoxide (CDP) is often the preferred drug because, unlike other benzodiazepines, it is soluble in water. However, rapid CDP hydrolysis in solution has been described. This would diminish plasma levels in chronic minipump studies and introduce the corelease of active compounds.


METHODS
Therefore, the present study aimed to explore the putative hydrolysis of CDP in aqueous solution over time and to identify the hydrolysis products. Moreover, we aimed to characterize the hydrolysis products for their in vitro (3H-flunitrazepam binding and oocyte electrophysiology) and in vivo (stress-induced hyperthermia paradigm) GABAA receptor potency.


RESULTS
CDP in solution hydrolyzed to the ketone structure demoxepam which was confirmed using mass spectrometry. The hydrolysis was concentration dependent (first-order kinetics) and temperature dependent. CDP exerted greater potency compared to demoxepam in vitro (increased activity at GABAA receptors containing α1 subunits) and in vivo (stress-induced hyperthermia), although 3H-flunitrazepam binding was comparable.


CONCLUSIONS
The classical benzodiazepine CDP is rapidly hydrolyzed in solution to the active compound demoxepam which possesses a reduced activity at the GABAA receptor. Chronic studies that use CDP in aqueous solution should thus be interpreted with caution. It is therefore important to consider drug stability in chronic minipump applications.
Vinkers
Christiaan H
CH
Department of Psychopharmacology, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands. c.h.vinkers@uu.nl
Korte-Bouws
Gerdien A H
GA
Toraño
Javier Sastre
JS
Mirza
Naheed R
NR
Nielsen
Elsebet Ø
EØ
Ahring
Philip K
PK
de Jong
Gerhardus J
GJ
Olivier
Berend
B
D000818:Animals; D001569:Benzodiazepines / Q000737:chemistry / Q000494:pharmacology*; D001831:Body Temperature / Q000187:drug effects; D002707:Chlordiazepoxide / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology; D002853:Chromatography, Liquid / Q000379:methods; D004355:Drug Stability; D005334:Fever; D006868:Hydrolysis; D015918:Infusion Pumps, Implantable; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D057507:Mice, 129 Strain; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D011869:Radioligand Assay / Q000379:methods; D011963:Receptors, GABA-A / Q000378:metabolism; D013997:Time Factors; D014316:Tritium
D011963:Receptors, GABA-A; D014316:Tritium; D001569:Benzodiazepines; D002707:Chlordiazepoxide; C000869:demoxepam