582 Substance-Related and Addictive Disorders
substances used by pulmonary inhalation and intravenous injection have the most rapid
onset of action, while those ingested by mouth and requiring metabolism to an active
product are much slower. (For example, after ingestion of certain mushrooms, the first
signs of an eventually fatal intoxication may not appear for a few days.) Intoxication ef-
fects usually resolve within hours to a very  few days. However, the body may completely
eliminate an anesthetic gas such as nitrous ox ide just minutes after use ends. At the other
extreme, some “hit-and-run” intoxicating su bstances poison systems, leaving permanent
impairments. For example, MPTP (1-methyl- 4-phenyl-1,2,3,6-tetrahydropyridine), a con-
taminating by-product in the synthesis of a certain opioid, kills dopaminergic cells and in-
duces permanent parkinsonism in user s who sought opioid intoxication. 
Functional Consequences of 
Other (or Unknown) Substance Intoxication
Impairment from intoxication with any subs tance may have serious consequences, includ-
ing dysfunction at work, social indiscretions, problems in interpersonal relationships, fail-
ure to fulfill role obligations, traffic accide nts, fighting, high-risk behaviors (i.e., having
unprotected sex), and substance or medication  overdose. The pattern of consequences will
vary with the particular substance.
Differential Diagnosis
Use of other or unknown substance, without meeting criteria for other (or unknown)
substance intoxication. The individual used an other or unknown substance(s), but the
dose was insufficient to produce symptoms that meet the diag nostic criteria required for
the diagnosis.