use disorder.
Diagnostic Features
Other (or unknown) substance intoxication is a clinically significant mental disorder that
develops during, or immediately after, use of either a) a substance not elsewhere ad-
dressed in this chapter (i.e., alcohol; caff eine; cannabis; phencyclidine and other halluci-
nogens; inhalants; opioids; sedatives, hypnotics , or anxiolytics; stimulants; or tobacco) or
b) an unknown substance. If the substance is known, it should be reflected in the name of
the disorder upon coding.
Application of the diagnostic criteria for other (or unknow n) substance intoxication is
very challenging. Criterion A requires development of a reversible “substance-specific
syndrome,” but if the substance is unknown, that syndrome usually will be unknown. To
resolve this conflict, clinicians may ask the in dividual or obtain co llateral history as to
whether the individual has experienced a similar episode after using substances with the
same “street” name or from the same source . Similarly, hospital emergency departments
sometimes recognize over a few days numerous presentations of a severe, unfamiliar in-
toxication syndrome from a newly available,  previously unknown substance. Because of
the great variety of intoxicating substances, Criterion B can provide only broad examples
of signs and symptoms from some intoxications, with no  threshold for the number of
symptoms required for a diagnosis; clinical judgment guides those decisions. Criterion C
requires ruling out other medical conditio ns, mental disorders, or intoxications.
Prevalence
The prevalence of other (or unknown) substance intoxication is unknown.
Development and Course
Intoxications usually appear and then peak minu tes to hours after use of the substance, but
the onset and course vary with the substanc e and the route of administration. Generally,