How long does Phencyclidine (PCP) stay in the system?

Detection Duration of Phencyclidine (PCP) in the Body

PCP can be detected in urine for approximately 1-4 days after a single use, but in chronic users, detection extends to approximately 1 week or longer after last use. 1

Detection Windows by Biological Matrix

Urine Detection (Most Clinically Relevant)

• Single dose: Detection window of 1.5 to 4 days 1
• Chronic users: Approximately 1 week after last use, with extreme cases showing even longer detection periods 1
• Urine provides the longest practical detection window among commonly tested fluids 1

Blood/Plasma Detection

• Most drugs of abuse, including PCP, can be detected at low nanogram per milliliter levels for 1 to 2 days in blood or plasma 1
• Maximum plasma PCP concentrations of 2.7 to 2.9 ng/ml are observed after 1-mg doses 2
• Blood/plasma ratios are approximately 1.0 with plasma protein binding around 65% 2

Oral Fluid (Saliva) Detection

• Detection window of 5-48 hours at low nanogram per milliliter levels 1
• Parent drug can be found in saliva 2

Other Matrices

• Hair: Provides the longest detection time overall, though specific timeframes for PCP are not detailed in the available evidence 1
• Sweat: Detection possible but shorter than urine 1

Pharmacokinetic Factors Affecting Detection

Elimination Half-Life

• Terminal phase half-life averages 21 ± 3 hours (harmonic mean 17 hours, range 7-46 hours) 2
• This relatively long half-life contributes to extended detection windows, particularly in chronic users 2

Metabolism and Excretion

• PCP is cleared principally by metabolism (91% of total clearance) rather than renal excretion 2
• After a 1-mg dose, 72.8% of the drug and metabolites are recovered in urine, with only 16% as unchanged PCP 2
• Approximately 31% consists of enzymatically hydrolyzable conjugates of hydroxylated metabolites 2
• Fecal excretion is minimal (3.4-4.7%) 2
• Oral bioavailability is estimated at 72% 2

Volume of Distribution

• Large volume of distribution averaging 6.2 ± 0.3 L/kg 2
• This extensive tissue distribution contributes to prolonged detection in chronic users 2

Clinical Considerations

Factors Prolonging Detection

• Chronic use: The most significant factor extending detection beyond the typical 1-4 day window 1
• Dose: Higher doses extend detection times 1
• Urine pH and concentration: Can affect detection sensitivity 1
• Individual metabolic variation: Renal and metabolic clearance varies between individuals 1

Testing Method Sensitivity

• Detection times depend heavily on the sensitivity of the analytical method used 1
• Modern LC-MS/MS and LC-HRMS methods can detect PCP at very low concentrations 3
• Commercial immunoassay test kits based on antigen-antibody interactions are available for screening 4

Important Caveats

The detection window can be significantly longer in heavy, chronic users compared to single-use scenarios, making it essential to consider use patterns when interpreting toxicology results 1. The wide range in elimination half-life (7-46 hours) also means substantial individual variation exists 2.

Acidification of urine may increase PCP clearance during acute intoxication treatment, potentially shortening detection windows 4, though this is primarily a therapeutic consideration rather than a forensic one.