Text Box: EFFECT OF KETAMINE ON PHENCYCLIDINE IMMUNOASSAYS (PCPIa) Hoffman RJ1, Saddock V2, Winnik G1, Nelson LS2, Hoffman RS2 1Maimonides Medical Center, Brooklyn, New York, USA. 2New York City Poison Control Center, New York, New York, USA Objective: Ketamine is a derivative of phencyclidine (PCP). PCPIa urine tests have significant cross-reactivity with other PCP congeners. Positive urine PCPIa associated with ketamine administration motivates us to evaluate the effect of ketamine on urine PCPIa. Methods: This is a blinded, anonymous study assaying urine of pediatric patients receiving parenteral ketamine. Patients (n=50) submitted urine prior to receiving ketamine and again 1-2 hours after receiving ketamine. Gas chromatography/ mass spectrometry was performed on all urine samples to detect PCP, ketamine and ketamine metabolites. All urine was tested by five different urine PCPIa to determine if ketamine administration caused with a change in PCPIa result from negative pre-treatment to positive post-treatment. PCPIa used included Syva EMIT® reagent and four different point of care testing devices manufactured by Forefront Diagnostics (Laguna Hills, CA), Princeton BioMeditech (Princeton, NJ), Roche Diagnostic Systems (Sommerville, NJ), and Technical Chemicals and Products (Pompano Beach, FL). Results: No urine contained PCP, no pre-treatment samples contained ketamine or metabolites and all post-treatment urine samples contained ketamine and metabolites. No urine was PCPIa positive. Conclusions: Ketamine and metabolites are present in urine 1-2 hours after parenteral ketamine administration. Urine collected 1-2 hours after ketamine administration was PCPIa negative. Possibly, cross-reacting ketamine metabolites are not present in urine 1-2 hours after administration but are present later. However, we find no evidence that ketamine administration results in positive PCPIa. 2419