Biochemical Measures of Drug Use

Biochemical measures have received considerable attention in the AOD field, however they tend to be of fairly limited value as stand alone measures. The relative merits of their use should be weighed against the context of assessment and treatment.

Urinalysis: When to use it

The vast majority of studies suggest that people provide valid information about their drug use under favourable conditions (eg. confidentiality). More recent studies suggest greater agreement between self-reported drug use and urine test results when a urinalysis is performed before an interview, and when measured over time.

Assessment - the context of the assessment or treatment, the stage of treatment, interviewing conditions and types of drugs used will influence clinical decisions about whether or not to conduct a urinalysis. Cost is a major consideration.

Urinalysis: What it aims to achieve

Urinalysis detects the presence or absence of drugs or their metabolites in urine. It cannot help to determine dosage, time of drug use, effect or related harms experienced by the user. Monitoring of drug use may comprise part of an agreed treatment agreement, or as part of a longer term treatment program (such as maintenance pharmacotherapies). For most drugs, there is a relatively brief ‘window for detection’ of 2-3 days.

Factors that may influence urine results

Dosage: the higher the dose, the more likely the drug will be detected (eg. 30mg codeine might be detected for 1-6 hrs after use, a 60mg dose between 1-10 hours)
Frequency: As drugs tend to accumulate in the body, the more frequently a drug is used, the more likely it will be detected.
Drugs are metabolised at different rates: (eg cocaine – a single dose may be detectable for a day or less but more frequent use may result in detection 2-3 days later. Regular or daily use of cannabis may result in its detection in urine for up to 3 weeks after ceasing use).

Hair Analysis

Detects the presence of drugs for the duration of the hair growth. As blood plasma contains drugs and their metabolites, they become embedded in the hair structure during keratinisation and are present throughout the life of the hair hence it is possible to estimate the time frame in which the drug was used. (Napoleon’s hair was found to contain arsenic; Keat’s hair laudanum). Commercially available hair colourants and peroxide bleach may reduce the drug levels (but not presence) of methadone and its metabolites.

Hair analysis is carried out at the Victorian Institute of Forensic Medicine using specific protocols. Analytical and interpretation issues are still to be resolved regarding the use of hair analysis for drug use. See Dawe et al (2002).

Adapted from: Dawe, et al. 2002, Review of diagnostic screening instruments for alcohol and other drug use and other psychiatric disorders, (2nd edn), Commonwealth Department of Health and Ageing, Canberra. pp. 99-102.

Resource Kit for GP Trainers on Illicit Drug Issues

Part B3 Clinical Process: Early Recognition & Screening