Institut für Rechtsmedizin, Ruprecht-Karls Universität, Vosstr. 2, D-69115 Heidelberg, Germany
* Institut für Rechtsmedizin, Johannes-Gutenberg Universität, Am Pulverturm 3, D-55131 Mainz, Germany

The effect of the cleansing carbohydrate drink The Ultimate Blend™ was investigated in 8 heavy cannabis users. Urine samples collected prior to and at last 2 hours after fluid intake were assayed by 3 manually (Triage^®, Toxi Quick^®, Quick Screen 6) and 4 automatically (Emit-st™, Abuscreen Online^®, Abbott ADx™, Cedia^® DAU) processed immunoassays. Changes in 11-nor-delta-9-carboxytetrahydrocannabinol concentration were confirmed by GC/MS, and, additionally, apperance, pH-value, creatinine concentration as well as [Na⁺], [K⁺], [Ca²⁺] and [Cl^-] were determined.

The decrease in concentrations of THCOOH, creatinine, [Na⁺] + [K⁺], [Ca²⁺] and [Cl^-] in final samples, expressed as a percentage of the initial values are shon in the following table. pH values decreased from 7.0 to 5.5.

	THCCOOH	Creatinine	[Na+]+[K+]	[Ca2+]	[Cl-]
range (%)	6-37	8-33	5-22	8-40	5-25
mean (%)	24.6	17.0	13.8	19.3	14.2
SD (%)	7.5	9.1	6.5	12.6	6.6

The ingestion of the drink could give rise to false negative results in immunological testing for cannabinoids depending on the starting concentration of drug metabolites and on the immunoassay or cut-off applied. There was a rather uniform decrease for creatinine and electrolytes in all samples collected afterwards, and dilution seemed to be the predominant effect of the carbohydrate drink. The measurement of "dilution" parameters can help to recognize urine samples that are less suited for urine screening and to take appropriate precautions against unreliable results from watery specimens.