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020 8510 5555

The Biochemistry Department provides a Drugs of Abuse screening service for the NHS and other clients.

The routine drug screening panel provided covers all the major classes of abused drugs together with qualitative detection of an array of prescribed medications. 

See below for contact details if further information is required.

The Drugs of Abuse screen

The screen detects abused drugs consumed within the preceding 2 to 3 days for most classes of drugs, however detection of some drugs, such as cannabinoids and diazepam may be possible for several weeks thereafter, please refer to table below for guidance on the typical time periods by which given compounds remain detectable in a patient's urine.

Drug clearance times (approximate)

Drug Group Approximate time drug remains detectable for: -
Opiates Up to 3 days
Methadone 2-3 days
Cocaine metabolites

2-3 days


3 days
Benzodiazepines 2-28 days (depending on specific drug taken)
Cannabis 2-10 days typical (depending on dosage - this may persist for up to one month post-consumption)
Barbiturates 1-3 days (with the exception of Phenobarbitone which may persist for up to 14 days following ingestion)

The detection limits employed by this laboratory conform to nationally accepted guidelines and are detailed below: -

Detection limits (Positive cut-offs)

Drug Group Detection limits in urine (ng/mL)
Opiates screen 300
Individual "Free" Opiates 300
6-monoacetylmorphine 10
Amphetamines screen 1000
Barbiturates screen 200
Benzodiazepines screen 300
Cocaine metabolites (Benzoylecgonine) 300
Cannabinoids screen 50
Methadone (parent compound) 500
EDDP (methadone metabolite) 500
Buprenorphine screen 5.0


Confirmation and interpretation of results

Confirmation of immunassay and GLC screening assay is performed by way of GCMS and LCMS techniques, where required. The interpretation of results for most drug classes is straightforward. However, the opiate results format may require the following clarification: -

  • A patient may be taking heroin (diamorphine) but this does not appear on the final report. This is because heroin has a very short half-life in the body, typically a few minutes and so is seldom detected.
  • The metabolic pathway of heroin progresses firstly through the 6-monoacetlymorphine (6MAM) metabolite and then to morphine. The presence of 6MAM is a confirmation that heroin has been ingested (and therefore metabolised.) This is present in samples for typically the first 12 hours after ingestion of heroin, (rising to 24 hours dependent on the size of dose of heroin taken.)
  • The major metabolite of heroin detected in urine samples is morphine. This should be detectable for 2 to 3 days after the last ingestion of heroin.
  • Codeine, or acetylcodeine, is present as a contaminant in “street” heroin, (produced as a by-product in the refinery of opium.) It is typically present in much lower quantities than morphine in a patient’s urine specimen and is reported accordingly.

Contact our lab...

For more information or if you have any comments about our service please contact the Drugs of Abuse Laboratory Lead. Tony Dedman on Tel: 020 8510 7189

Last updated: 08 March 2016