Medicinal Use and Abuse
PCP (l-phenylcyclohexylpiperidine), was first synthesized in 1926. Its anesthetic properties were discovered in 1956 and, based on clinical trials started in 1957, it appeared to be ideally suited as an anesthetic in individuals with compromised cardiac function. Clinical trials were discontinued in 1963 after the discovery of a high incidence of post-anesthetic psychosis. The drug continued to be used legitimately as a veterinary tranquilizer for a period of time after its use in humans was discontinued. It was placed on DEA Schedule II in 1978 when its illicit use was discovered. Legal manufacture was halted in April 1979. This makes PCP the second drug tested under the federal guidelines for which there can be no medical explanation of a positive result, heroin being the first.
Phencyclidine is abused due to its hallucinogenic properties. Manifestations of intoxication include confusion; agitated, combative bizarre behavior; nystagmus; ataxia; muscle rigidity; and hypertension. Phencyclidine is typically administered by smoking, although it can also be administered by oral, intranasal, or intravenous routes. In the smoked form, PCP is sprayed onto parsley or marijuana and smoked as a cigarette, known as a Sherman. On the street, PCP is commonly called Angel Dust, Peace Pill, or Lovely. When used simultaneously with cocaine, it may be called Tick. Unlike marijuana and cocaine, PCP has not achieved widespread national abuse. Its use is not uncommon, however, in the coastal cities of New York, Baltimore, Washington, Los Angeles, and San Francisco.
Metabolism and Analytical Issues
Phencyclidine and its metabolites are primarily excreted in the kidney. About 15% of the parent compound is excreted in the urine unchanged. Hydroxylation and conjugation make up most of the identified metabolizes. Phencyclidine is typically detected in the urine for about a week, although it can be detected 2 to 4 weeks after chronic use. Acidic urine facilitates the excretion of PCP.
The target analyte of the PCP immunoassay is the parent drug, although there is some limited cross-reactivity with PCP metabolites and analogs. Some PCP analogs are psychoactive and are controlled (Schedule I or II) substances; however, they will not produce a PCP-positive result by GC-MS. Ketamine, the only legally prescribed analog, does not show any cross reactivity to the PCP immunoassay.