9.2.1 General considerations
Chronic misuse of drugs is incompatible with safe vehicle driving. Careful individual assessment must be made of drivers who misuse alcohol or other substances (prescribed or illicit). Substance misuse may not be confined to a single drug class, and people may use multiple substances in combination. In addition, people who misuse substances may change from one substance to another. Occasional use of these drugs also requires very careful assessment. In particular, the health professional should be satisfied that the use of these drugs is not going to affect a commercial vehicle driver in the performance of their duties.
During clinical assessment, patients may understate or deny substance use for fear of consequences of disclosure. The acute and chronic cognitive effects of some substance use also contribute to difficulty in obtaining an accurate history and identification of substance use. Assessment should therefore incorporate a range of indicators of substance use in addition to self-report.
Secondary opinion from an appropriate specialist, such as an addiction medicine specialist or addiction psychiatrist, may be necessary, and further assessment and/or ongoing biological monitoring (e.g. supervised drug screening) by the treating doctor may be indicated, including relevant investigations, particularly in the case of commercial vehicle drivers. In particular, people with combined substance use disorder and mental illness (‘dual diagnosis’) may have a level of complexity requiring specialist assessment.