522 Substance-Related and Addictive Disorders
toms have not been clearly established in hu mans, and therefore the withdrawal criterion
is not included in the diagnosis of phencyclidine use disorder. 
Associated Features Supporting Diagnosis
Phencyclidine may be detected in urine for up to 8 days or even longer at very high doses. In
addition to laboratory tests to detect its presence, characteristic symptoms resulting from
intoxication with phencyclidine or related su bstances may aid in its diagnosis. Phencycli-
dine is likely to produce dissociative sympto ms, analgesia, nystagmus, and hypertension,
with risk of hypotension and shock. Violen t behavior can also occur with phencyclidine
use, as intoxicated persons may believe that  they are being attacked. Residual symptoms
following use may resemble schizophrenia. 
Prevalence
The prevalence of phen cyclidine use disorder is unknown.  Approximately 2.5% of the pop-
ulation reports having ever used phencyclidine. The proportion of users increases with
age, from 0.3% of 12- to 17-year-olds, to 1.3% of 18- to 25-year -olds, to 2.9% of those age 26
years and older reporting ever using phencyclid ine. There appears to have been an in-
crease among 12th graders in both ever used (to 2.3% from 1.8%) and past-year use (to 1.3%
from 1.0%) of phencyclidine. Past-year use of  ketamine appears relatively stable among
12th graders (1.6%–1.7% over the past 3 years).
Risk and Prognostic Factors