Clinical Drug Testing

Excerpt

Clinical drug testing analyzes plasma, serum, or urine to detect the presence or absence of a drug or its metabolites. As the metabolization rate of drugs differs, the detection window for specific drugs or metabolites varies. Clinical drug testing plays an essential role in managing poisoning because the self-report of the drugs taken is often unreliable. The same is true in treating addiction disorders because clinical examination, patient self-reporting, and hetero-anamnesis will underreport the actual incidence of substance use.

Drug testing can be indicated in cases of suspected overdose or when monitoring abstinence in patients treated for addiction or in pain management clinics. No universal standard currently exists in clinical drug testing for addiction identification, diagnosis, treatment, medication monitoring, or recovery. Guidelines do exist for laboratory analyses of poisoned patients.

In poisoning cases, the indications for laboratory assays are to confirm the suspicion of poisoning when this is in doubt and to influence patient management. Indications for laboratory assays may include establishing or eliminating the need for further investigations or administration of antidotes, hemodialysis, or other invasive extracorporeal epuration methods. Clinical drug testing may also be needed to determine if the cessation of treatment is indicated or to plan the re-institution of chronic therapy.

In the intensive care unit, clinical drug testing is used to aid in the diagnosis of brain death and to determine the suitability of potential organ donors. The use of laboratory investigations out-of-hours should be restricted to those instances when an urgent result is needed to guide immediate patient management. It may also be appropriate to obtain and store samples for later analysis.