Development of a stereospecific radioimmunoassay for the analysis of zopiclone and metabolites in urine.
A sensitive and specific radioimmunoassay has been developed, allowing the stereospecific detection of nanogram amounts of (+)- and (-)-enantiomers of zopiclone and its major metabolites in urine, without prior extraction or purification. Antisera were obtained from two series of four rabbits, immunized with optically pure (+)- and (-)-N-hemisuc-cinyldesmethylzopiclone, conjugated to bovine serum albumin according to the active ester method. The assay was stereospecific, allowing discrimination between the two enantiomers of N-desmethylzopiclone with mutual cross-reactivities below 2%. Substantial cross-reaction was observed with the parent compound, although lower than expected, and to a lesser extent with the N-oxide metabolite. A selection of hypnotics, anxiolytics, antidepressants and some other widely used drugs did not interfere with the assay (< 0.1%), when tested at a concentration level of 10 micrograms/ml. The sensitivity of the assay was 50 pg/ml and 10 pg/ml for the (+)- and (-)-enantiomers, respectively. The binding assay described here was used to evaluate the stereoselective excretion pattern of zopiclone. Analysis of cumulative excretion samples from a volunteer revealed a mean metabolic excretion ratio (+)/(-) of 2.2, ranging from 1.7 (7 h) to 4.4 (36 h) A mean excretion ratio (+)/(-) of 2.5 +/- 1 was calculated after analysis of urine samples from 20 patients receiving zopiclone as a hypnotic daily.
Mannaert
E
E
Laboratory of Toxicology, Katholieke Universiteit Leuven, Belgium.
Tytgat
J
J
Daenens
P
P
D000818:Animals; D000918:Antibody Specificity; D053961:Azabicyclo Compounds; D003429:Cross Reactions; D006801:Humans; D006993:Hypnotics and Sedatives / Q000652:urine*; D007106:Immune Sera; D010879:Piperazines / Q000652:urine*; D011817:Rabbits; D011863:Radioimmunoassay / Q000379:methods*; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D014614:Vaccines, Synthetic
D053961:Azabicyclo Compounds; D006993:Hypnotics and Sedatives; D007106:Immune Sera; D010879:Piperazines; D014614:Vaccines, Synthetic; C515050:zopiclone; C053229:N-desmethylzopiclone