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Medicinal Cannabis On The Precipice Of Proliferation, Caution Advised For Business Leaders

The Drug Detection Agency (TDDA) is seeing increased detection rates of cannabis in workplace drug screenings. It attributes the rise to the proliferation of medicinal cannabis and easier access to the substance. In house data from its Imperans IT platform as well as anecdotal evidence from employees and clients paint a risky picture.

“Business leaders need to understand, mitigate risks, and address the issue immediately,” says Glenn Dobson, CEO, TDDA. “We’re seeing cannabis trigger our testing devices regularly which isn’t particularly new. What is new is that people in safety sensitive workplaces then show up with a prescription for cannabis. But just because the substance is legal doesn’t mean it’s safe to take it and get behind the wheel of a 40-ton truck.”


New Zealand’s Medicinal Cannabis Act came into effect in 2020. Growers and distributors needed time to meet the government standards in terms of product development and quality assurances. TDDA attributes the gap between 2020 and 2023 detection rates to regulatory pressures, but now believes the situation is at a tipping point. Employers need to understand how to grapple with the challenge of integrating this change into existing drug and alcohol policies.

TDDA recommends businesses take professional advice to understand the issue of medicinal cannabis within their workforce. Like any prescription medication, such as opioids or prescription painkillers, there need to be clear guidelines on company and employee expectations. Businesses must integrate professional guidance into their substance polices and update them immediately to manage medicinal cannabis.

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“Every business will eventually need to deal with substance issues, but having easy access to high grade cannabis products will accelerate and amplify those issues. Kiwi companies need to update their drug and alcohol policies immediately,” says Dobson.

TDDA further recommends businesses consult with experts on drug and alcohol policies, employment law, and a doctor trained as a medical review officer (MRO). Each are needed to craft an operational plan that mitigates workplace risks, and protects a business’s bottom line. Understanding the pharmacological aspects of medicinal cannabis, testing programmes and technologies, employee rights and employer obligations is essential for businesses to protect their people and maintain a safe and compliant workplace.


Medicinal cannabis products may contain the psychoactive component in marijuana, THC (tetrahydrocannabinol), be CBD-based, or both, posing unique challenges for employers. Those in safety sensitive industries will be most affected. Employers must understand their duty of care under the Employment Relations Act 2000, their compliance requirements for the Health and Safety at Work Act 2015, operating within the Privacy Act 2020. Employment information as well as medical testing information can quickly fall afoul of privacy laws.

Employers have an obligation to ensure the safety of all employees in the workplace. But only if a good substance policy is in place will employees have an obligation to inform their employer of relevant prescription medications.

Employers must also carry out testing in a fair, compliant, and transparent manner. It's essential to update workplace drug and alcohol policies to include guidelines for medicinal cannabis.

“If an employee is affected by medicinal cannabis at work, even if its prescribed, it will affect their ability to safely execute their duties. The substance creates a minefield to navigate, and it poses a risk to the employee, their peers, the business and the public. Employers must understand these products can adversely affect cognitive abilities and motor function,” says Dobson.


THC, the psychoactive component in many medicinal cannabis products, impairs cognitive functions and motor skills, posing risks in any industry. Additional symptoms include issues with memory, attention, decision-making skills, poor judgment, mood swings and irritability.

“CBD or low THC forms of this drug are particularly problematic. If an employee has a prescription it’s important to work with a MRO to understand if the employee’s needs are in alignment with the requirements for the role,” says Dobson.


TDDA recommends businesses review and update their drug and alcohol policies, and ensure policies are clear and effectively communicated. It also recommends education sessions for managers and employees alike, as well as enhanced training for supervisors to recognise risk in the workplace. Seek guidance from subject matter experts who understand your business and its requirements. If enacting a drug and alcohol testing programme, engage qualified third party experts.

“Medicinal cannabis is here, and it’s in New Zealand’s workplaces. It can be a high potency substance and it needs to be treated as one, it brings risk to any workplace. If someone is driving a company car, you need to have a plan to address the issue. Don’t get caught on the back foot,” says Dobson.

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