Prolonged Ketamine and Norketamine Excretion Profiles in Urine After Chronic Use: A Case Series.

PURPOSE/BACKGROUND: Ketamine (K) is used as a party drug with hallucinogenic properties with a half-life of about 2.5 hours. Data are available with respect to the detection window (ie, when a person is still tested positive for the drug and/or metabolite after use) of K after single use. Nevertheless, no data are available with respect to the detection window of K in urine after chronic use.

METHODS/PROCEDURES: This retrospective case series describes 7 patients with K dependency as their main addiction who have been admitted to an addiction center for K detoxification. Their abstinence-oriented care involved routine urinary screening of K and its metabolites, as well as traditional drugs of abuse, such as cocaine and cannabinoids.

FINDINGS/RESULTS: Urine samples remained positive for all the cases identified after 22 to 96 days. A peak detection period of 61, 40, and 96 days for K, norketamine, and dehydronorketamine, respectively, measured using liquid chromatography-tandem mass spectrometry at a cutoff concentration of 1.0 ng/mL, is defined. The K/norketamine and K/dehydronorketamine ratios varied over time between 0.33 and 3.06, and 0.01 and 0.36 for all patients, respectively, implying a large interindividual variation in K metabolism.

IMPLICATIONS/CONCLUSIONS: Ketamine and its metabolites have a prolonged excretion profile in urine, which requires frequent measurements (at least weekly) to guide abstinence treatment. Further research is needed to develop an algorithm that can differentiate new K use from residual urinary K excretion in urine of chronic daily users.