Clardy and Ragle examined the stability of phencyclidine (PCP) in stored blood using 41 specimens obtained from arrested individuals. After an initial quantification, the specimens were stored at room temperature for up to 18, months. Phencyclidine in these specimens was quite stable during this time period. In 30 of the 41 specimens, the difference between the original and the subsequent analysis was <10% in the remaining specimens, the difference was  30%.

The regression line correlating the original blood concentration and the reanalyzed blood concentrations had a slope of 1.00. Most of the observed differences were attributed to variations in the method. Other studies have demonstrated similar results with PCP in blood specimens for periods up to 5 years when the blood was stored in the refrigerator or freezer. The stability of PCP in urine was studied by Hughes et al.

Five drug free urine specimens were fortified with PCP at 3 different concentrations: 21, 62, and 129 ng/mL The specimens were stored either at room temperature or refrigerated temperature, and were reanalyzed after 3 months and 6 months. All specimens were within 25% of the original concentration after 3 months at both temperatures. More than 50% of PCP originally added was detected after 6 months. Dugan et al. measured PCP concentrations in 60 physiological urine specimens after storage in the freezer for 1 year. There was an average decrease in PCP Concentration of 14% with a range of +11 to -51%.

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