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Interpretive Handbook

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Test 89069:
Phencyclidine Confirmation, Meconium

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Phencyclidine (PCP) was originally developed as an anesthetic in the 1950s but later was abandoned because of a high frequency of postoperative delirium with hallucinations. It was classed as a dissociative anesthetic because, in the anesthetized state, the patient remains conscious with staring gaze, flat facies, and rigid muscles.(1) PCP binds with high affinity to sites located in the cortex and limbic structures, resulting in blocking of N-methyl-D-aspartate (NMDA)-type glutamate receptors.(1) PCP became a drug of abuse in the 1970s because of its hallucinogenic effects.(1,2)

 

PCP is approximately 65% protein bound and has a volume of distribution (Vd) of 5.3 to 7.5 L/kg. The drug is metabolized by the liver via oxidative hydroxylation and has a dose-dependent half-life ranging from 7 to 46 hours.(2)

 

Meconium is the first fecal material passed by the neonate. Meconium forms in the first trimester of pregnancy but is seldom excreted before the 34th week. It is composed of approximately 70% water, bile acids, cholesterol, squamous cells, protein and drug metabolites, and no bacteria are normally present. Prebirth excretion of meconium is a sign of fetal distress.

 

Because drugs and metabolites can accumulate in meconium, assessment of meconium for the presence of illicit drugs can be an indicator of maternal drug use during pregnancy. Illicit drug use during pregnancy can have a profound effect on fetal development.

Useful For Suggests clinical disorders or settings where the test may be helpful

Detection of in utero drug exposure up to 5 months before birth

Interpretation Provides information to assist in interpretation of the test results

The presence of phencyclidine in meconium is indicative of in utero drug exposure up to 5 months before birth.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Because the results of this test may have legal ramifications, it is recommended that testing be performed using chain-of-custody. A kit including all the materials necessary to complete chain-of-custody is available to ensure the test results are appropriate for legal proceedings.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

Positives are reported with a quantitative LC-MS/MS result.

Cutoff concentrations

PCP by LC-MS/MS: >10 ng/g

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. O'Brien CP: Drug addiction and drug abuse. In Goodman and Gilman's the Pharmacological Basis of Therapeutics. 11th edition. Edited by LL Brunton, JS Lazo, KL Parker. McGraw-Hill Book Company, Inc, 2006

2. Baselt RC: Phencyclidine. In Disposition of Toxic Drugs and Chemicals in Man. Eighth edition. Edited by RC Baselt. Foster City, CA, Biomedical Publications, 2008, pp 1735