Nabiximols and Urine Screening: A Dose Correlation Is Not an Impairment Measurement
A urine cannabinoid screen can correlate with a prescribed nabiximols dose without measuring impairment. In a small multiple-sclerosis study, the relationship concerned ongoing treatment exposure and laboratory response. It did not establish an acute driving-risk threshold or a way to calculate an individual’s exact dose from one specimen.
Who was studied
Birke and colleagues examined 17 people with multiple sclerosis who had used their current nabiximols dose for at least two months. Blood and urine were collected at least two hours after the last application, according to the patients’ reports.
The researchers compared a commonly available urine immunoassay with gas chromatography–mass spectrometry measurements. Urine results were normalized to creatinine to address variation in urine concentration. They also investigated the effect of enzymatic hydrolysis during sample preparation.
The assay measured a response to several compounds
The creatinine-normalized immunoassay result correlated significantly with daily dose, both without hydrolysis and after hydrolysis. The reported correlation coefficients were 0.675 and 0.650, respectively. Selectively measured THC-COOH in urine and plasma also correlated with dose.
The immunoassay was not specific to THC-COOH. The paper describes responses to several cannabinoid compounds and metabolites. Its numerical result therefore should not be relabeled as a direct, selective measurement of active parent THC.
Hydrolysis changed the assay response, illustrating that sample preparation can affect what is measured. The researchers also encountered many concentrations below quantification for some analytes, limiting their ability to calculate reliable cannabinoid ratios.
A group correlation is not an individual dosing formula
Participants used other medications, and metabolic differences could influence the relationships. The doses and last-application intervals relied on patient information. A cross-sectional association between people does not validate the precision of monitoring dose changes within one person.
The study did not test acute impairment or distinguish prescribed use from an additional cannabis exposure with a universally reliable rule. Our discussion of driving reports in a nabiximols safety registry addresses another type of evidence. Neither registry reports nor a urine dose correlation can replace an individualized assessment of function at the relevant time.
Primary research
Correlation of Nabiximols Dose to Steady-State Concentrations of Cannabinoids in Urine Samples from Patients with Multiple Sclerosis. DOI: 10.3390/jcm11133717.
