A screening method for establishing laxative abuse.

Abuse of laxatives, most of them belonging to the group of colonic stimulants or cathartics, can cause various disorders. Extensive diagnostic work can be avoided by early toxicological screening of the suspected patients with respect to laxatives. Because no screening method of this kind was available, we developed a procedure with which all phenolic and anthraquinone laxatives--except sodium picosulfate--can be detected in urine. This method is based on high-performance thin-layer chromatography in two systems after pretreatment of a 20-mL urine sample with beta-glucuronidase and subsequent column extraction. The procedure is very sensitive: at least 32 h after a single dose of bisacodyl, danthron, phenolphthalein, or sennoside, the drug can be detected in the urine. Bisoxatin and oxyphenisatin are still detectable in the urine 18 h after intake. The method is also highly specific; none of 73 other drugs interfered in either of the two chromatographic systems. This procedure can be helpful for the early diagnosis of laxative abuse.