Medicinal cannabis may provide benefits for some patients, but like other medicines, it can also cause side effects and may not be appropriate for everyone.
The effects can vary depending on the product, the amount taken, the balance of cannabidiol (CBD) and tetrahydrocannabinol (THC), other medicines being used and the individual patient.
In New Zealand, medicinal cannabis products are available on prescription, and healthcare professionals can consider a patient’s medical history, current medicines and the potential risks and benefits before prescribing.
Possible Side Effects of Medicinal Cannabis
Side effects can vary considerably between individuals and products.
Depending on the medicine and its CBD or THC content, patients may experience effects such as:
- Drowsiness or tiredness
- Dizziness
- Changes in concentration or attention
- Nausea
- Changes in mood
- Impaired coordination or slower reactions
Not everyone will experience these effects, and their severity may vary.
Patients who experience an unexpected or concerning reaction should seek advice from their healthcare professional. The Ministry of Health also advises patients that suspected adverse reactions can be reported through New Zealand’s medicine-safety system.
CBD and Side Effects
CBD (cannabidiol) has little-to-no psychoactive effect and is used in some medicinal cannabis products available in New Zealand.
However, the absence of an intoxicating effect does not mean CBD products are free from potential side effects or interactions.
A healthcare professional should consider other medicines a patient is taking when assessing whether a medicinal cannabis product is appropriate.
THC and Side Effects
THC (tetrahydrocannabinol) is the cannabinoid primarily associated with the psychoactive effects of cannabis.
Medicinal cannabis products containing THC may affect concentration, coordination, reaction time and a person’s ability to perform activities safely.
The effects can differ according to the product, dose and individual response.
Medicinal Cannabis and Driving
Driving requires particular caution.
New Zealand law states that people must not drive if a drug affects their ability to drive safely. THC is specifically included among the drugs covered by New Zealand’s drug-driving laws.
NZ Transport Agency guidance advises people taking prescription medicines to follow the instructions provided by their doctor, pharmacist or medicine manufacturer. If a medicine causes symptoms such as drowsiness, dizziness, blurred vision, slower reactions or difficulty concentrating, the person should not drive.
Patients using medicinal cannabis should discuss driving with their healthcare professional, particularly when using products containing THC.
Interactions With Other Medicines
Medicinal cannabis may be used by people who are already taking other prescription or non-prescription medicines.
For this reason, patients should tell their healthcare professional about the medicines and supplements they use before starting medicinal cannabis.
The Ministry of Health states that health professionals assessing medicinal cannabis treatment will consider a patient’s medical history and other medicines when weighing the potential risks and benefits.
Product Type and THC/CBD Content Matter
Medicinal cannabis is not a single product.
Products available in New Zealand can contain CBD, THC or combinations of cannabinoids and are available in different formulations. These include oral dosage forms and certain dried cannabis products intended for specified methods of administration.
This means the potential effects and risks of one medicinal cannabis product should not automatically be assumed to apply in exactly the same way to another.
Who Should Take Extra Care?
Whether medicinal cannabis is appropriate depends on the individual.
Medical history, other medicines, the reason for treatment, possible side effects and the specific cannabis product may all need to be considered.
Patients should discuss their individual circumstances with an appropriate healthcare professional rather than changing treatment or dosage themselves.
Quality Standards in New Zealand
Medicinal cannabis products supplied under New Zealand’s Medicinal Cannabis Scheme are subject to minimum quality standards.
These standards are designed to provide assurance about product quality and consistency. Importantly, the Ministry of Health states that meeting the minimum quality standard does not itself represent an assessment of a product’s safety or effectiveness.
This distinction is important when considering claims made about medicinal cannabis products.
Balancing Potential Benefits and Risks
Medicinal cannabis should be considered in the same careful way as other treatment options.
Potential benefits need to be weighed against possible side effects, interactions with other medicines, the patient’s circumstances and the strength of evidence for the condition being treated.
Treatment decisions should therefore be made with an appropriately qualified healthcare professional.
Official Information & Further Reading
For official New Zealand guidance:
Medicinal Cannabis Information for Consumers — Ministry of Health
Information for consumers about medicinal cannabis
Medicinal Cannabis Information for Health Professionals — Ministry of Health
Information for health professionals
How Medication Affects Driving — NZ Transport Agency Waka Kotahi
NZTA medication and driving guidance
Important
This information is provided for general educational purposes only and is not medical advice. Medicinal cannabis may not be appropriate for everyone. Always discuss medicines, side effects, potential interactions and treatment decisions with a qualified healthcare professional.
