The exponential growth in the number of Canadians with a medical marijuana prescription, combined with the pending legalization of pot for recreational use, is giving employers coughing fits.

Employers are obliged to accommodate staff with a prescription, a duty that will be particularly challenging in safety-sensitive positions.

Alison McMahon, CEO of Edmonton-based human resources consultancy TwoFold, says employers will have to work with physicians on fitness-for-duty assessments. They will have to ask how and when an employee doses, how he or she is cognitively or otherwise impaired by the dose, and about their duties. Then, the physician has to give their opinion of whether or not an employee can still, say, operate heavy equipment. “One employee may only dose in the evening,” she says, “but another, because he has Parkinson’s disease, may need to consume cannabis on a regular basis to get relief from the movement disorder that comes along with that disease.”

McMahon says prescriptions for medical marijuana aren’t usually as detailed as those for, say, antibiotics. “It won’t say, ‘Take every six hours,’ ” she says. “It’s more of a self-dosing regimen, but what I have seen is a physician make a recommendation for what a person’s daily allowance should be, and an agreement to the time of day they consume.”

Be sure to watch for more on this developing area of human resource practice