Introduction Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 References

The Patient Scenario
A new patient is assessed using several risk evaluation tools (ORT, CAGE-AID) and is considered to be at moderate-to-high risk of substance abuse/misuse. She is already prescribed numerous controlled substances for treatment of chronic pain, depression and anxiety. She denies any use of illicit or recreational drugs.

A lab-based urine immunoassay screen is ordered.

The Test

Laboratory-based immunoassay screen

The Test Results
Test results are consistent with her prescribed medications, with the exception of the presence of ∆-9-tetracannabinol (THC).

The Test Interpretation

The following are consistent with the results obtained, except:


*Available as unlicensed medicine

The Physician’s Next Step
Having confirmed the presence of THC, the ordering physician must explore the laboratory finding in the context of the clinical setting. In an increasing number of states, the therapeutic value of the cannabinoid molecule, including that obtained from medical marijuana, is now being recognized.

Unfortunately, the actual source of the molecule is known only to the user. While there are sophisticated tests which can distinguish between synthetic Δ-9-THC and herbal cannabis (tetrahydrocannabivarin [THCV]), they are expensive and at the present time, restricted to the research setting.

What would you do next?


An increasing number of states have decriminalized the use of marijuana for medical treatment. These state laws allow physicians to recommend use of marijuana for medical purposes, but the fact remains that this is in direct violation of federal regulations. Marijuana “pharmacies” do exist, but it is incumbent upon the recommending physician to determine the level of personal and professional risk associated with such recommendations. The utility of the cannabinoid molecule should not be lost in the controversy surrounding the most common mode of delivery, smoking.

The Final Outcome
At the present time, the appropriate role of medical marijuana is yet to be determined. By convention, where state and federal laws differ, the more stringent law prevails. The case of medical marijuana has become a confusing and muddied exception to this rule. Until this issue is resolved, physicians who recommend or support their patients’ choice to use medical cannabis will continue to place themselves at medicolegal risk.

Naturally occurring cannabis and synthetic THC are indistinguishable by conventional testing.
For practical purposes, the prescription of any THC-containing products (ie, dronabinol or liquid medical marijuana) makes the identification of drug testing impossible. There are other ways clinically to detect smoked cannabis, including asking the patient or detection of carbon monoxide.

Cone EJ, et al. Forensic Science International. 2010;198(1):58-61.

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Case 1:
Low back pain

Case 2:
High-risk patient

Case 3:
Activity-related pain

Case 4:
Escalating opioid doses

Case 5:
pain patient