A new, pharmacologically active metabolite of cocaine, ethylcocaine, has been reported in individuals after concurrent use of cocaine and ethanol. Formation of ethylcocaine may contribute to the common coabuse of these two drugs and the apparent danger of this practice. We have identified a nonspecific carboxyl-esterase that catalyzes the ethyl transesterification of cocaine to ethylcocaine in the presence of ethanol. In the absence of ethanol, this human liver esterase catalyzes the hydrolysis of cocaine to benzoylecgonine, a metabolite that is inactive as a psychomotor stimulant. A second human liver esterase is also described. This enzyme catalyzes hydrolysis of cocaine to ecgonine methyl ester, also inactive as a stimulant. These two liver esterases may play important roles in regulating the metabolic inactivation of cocaine.
We have developed a simplified xylose assay procedure that requires only 10 min and requires 50 microL of serum or 5 microL of urine. The reaction with phloroglucinol is more sensitive than the classic p-bromaniline color reaction, and requires only 4 min of heating for color development. A single reagent is mixed with the specimen directly, without prior protein precipitation. Analytical recovery of xylose added to serum was quantitative; precision studies resulted in a between-day coefficient of variation of 5.2%. Glucose, which has significant potential for interference in most other xylose procedures, reacts under the test conditions only to the extent of 70 mumol of apparent xylose per liter for a 5.5 mmol/L solution of glucose. The new procedure has been valuable in the assessment of malabsorption, especially in children and infants, where serum xylose is the preferred measurement.
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