If you take opioid medicines, tell your medical cannabis prescriber and pharmacist before any cannabis-based medicine is considered. The useful patient action is disclosure, not changing opioid treatment yourself.
Opioids include medicines such as codeine, morphine, oxycodone, tramadol, buprenorphine and fentanyl. Some are tablets or liquids. Some are patches. Some are used for pain, and buprenorphine or methadone can also be used in opioid substitution treatment. Whatever the reason, the prescriber needs the full picture.
This article does not tell patients to stop, reduce, combine, switch or change opioid dosing. It explains what to disclose so a clinician can assess sedation, dizziness, falls, alcohol or substance use, side effects, interactions and driving or work-safety risk.
If you are new to the wider medical cannabis process, start with the MCPH patient guide. For adjacent safety reading, use medical cannabis and medication interactions and medical cannabis side effects.
The short answer
Tell the prescriber:
- the name of every opioid medicine;
- the strength, form and how it is prescribed;
- whether it is regular, as-needed, a patch, a liquid, a tablet or another form;
- who prescribes it;
- whether there have been recent changes;
- any drowsiness, dizziness, falls, confusion, fainting, breathing problems, nausea, constipation or other side effects;
- alcohol use, non-prescribed drugs, sedating medicines, sleeping tablets, benzodiazepines, gabapentinoids, antidepressants, antihistamines and supplements;
- any history of substance-use concerns or opioid dependence treatment.
Do not leave something out because it feels awkward or because the opioid dose seems small. Interaction and sedation questions are normal parts of prescribing and pharmacist review.
Why opioids matter in a cannabis assessment
Opioids can cause drowsiness, dizziness, confusion and impaired coordination. Some opioid medicines can also be affected by alcohol or other sedating medicines. Medical cannabis can also cause drowsiness, dizziness, mood changes and impairment, especially where THC is involved.
The issue is not moral judgement. It is whether the combination of medicines, symptoms and risk factors is safe enough to consider. A prescriber may need to think about:
- sedation and daytime sleepiness;
- falls, fainting or unsteadiness;
- breathing conditions, sleep apnoea or severe chest disease;
- alcohol or other substance use;
- mental health history and previous adverse cannabis reactions;
- driving, machinery, caring duties and safety-critical work;
- other medicines that affect alertness or how medicines are processed.
The NHS medical cannabis page says CBD and THC can affect how other medicines work. NHS opioid medicine pages also warn about drowsiness, dizziness and alcohol-related side effects for some opioid medicines. A prescriber or pharmacist is the right person to interpret what matters for a specific patient.
What to bring to the consultation
Bring a current medicines list. If possible, use the repeat prescription list, NHS app medicine list, clinic letters or the Summary Care Record from the GP surgery. A photo of the medicine label can help if the appointment is remote.
For each opioid, include:
- medicine name;
- strength;
- form, such as tablet, capsule, liquid, patch or injection;
- how it is prescribed;
- whether it is taken regularly or only when needed;
- when it started;
- who prescribes it;
- recent changes, missed doses or supply issues;
- side effects or concerns.
Also include non-opioid medicines and substances that may matter. This includes gabapentin or pregabalin, benzodiazepines, sleeping tablets, antidepressants, antipsychotics, antihistamines, muscle relaxants, alcohol, over-the-counter medicines, supplements and any non-prescribed cannabinoid use.
What to say about side effects and falls
Tell the prescriber about side effects in ordinary language. You do not need to diagnose the cause.
Useful details include:
- “I get drowsy after taking this.”
- “I feel unsteady in the morning.”
- “I have fallen or nearly fallen.”
- “I get confused, forgetful or slower to react.”
- “I feel faint or dizzy.”
- “I have breathing problems, sleep apnoea or use oxygen.”
- “Alcohol makes the side effects worse.”
- “I have used cannabis before and it made me anxious, unwell or too sedated.”
These details can change the risk discussion. They may also affect whether a pharmacist needs to review the medicine list before any cannabis-based product is considered.
If severe drowsiness, breathing difficulty, collapse, severe confusion or another urgent symptom occurs, use urgent NHS routes rather than waiting for a routine cannabis clinic reply.
What not to do from an article
Do not change opioid dosing because of this article. Do not stop a long-term opioid suddenly because you are considering medical cannabis. Do not combine medicines to test the effect. Do not use alcohol to judge tolerance. Do not hide non-prescribed opioid or cannabis use from the prescriber.
If opioid medicines have not worked well enough, caused side effects, or been unsuitable, that may be relevant to the wider treatment history. It still needs clinician review. Medical cannabis should not be presented as an opioid replacement plan made by the patient.
For access discussions, previous treatment history can matter. Some clinics look for at least two relevant treatments that have not worked well enough, caused problems, or been unsuitable. If opioids are part of that history, explain what happened and let the prescriber decide how relevant it is.
Driving, work and daily safety
Opioids and cannabis-based medicines can both affect alertness. GOV.UK drug-driving law includes a medical defence for certain prescribed medicines only where the medicine is prescribed and taken as directed and the person is not impaired. That is not the same as saying a patient is cleared to drive.
Tell the prescriber if you drive, operate machinery, work at height, care for someone else, or have a safety-critical job. Also tell them if fatigue, pain, dizziness or medicines already affect concentration or reaction time.
If a cannabis-based medicine is ever prescribed, driving and safety advice needs to come from the prescriber and the relevant official guidance, not from an article.
Questions to ask a prescriber or pharmacist
Useful questions are practical and bounded:
- Which of my opioid medicines matter most for sedation or interaction review?
- Do any of my other medicines add to drowsiness, dizziness or falls risk?
- Should a pharmacist review my full medicines list before a decision is made?
- What side effects would make you want me to contact the clinic promptly?
- How should I report falls, near-falls, confusion or breathing symptoms?
- How does my driving or work-safety situation affect the assessment?
- What information do you need from my GP surgery, pain clinic or pharmacy?
These questions do not ask for a product or a dose. They help the clinician assess risk.
FAQ
Can I take medical cannabis with opioids?
This article cannot decide that. Some patients may be assessed while taking opioids, but the decision depends on the medicines, doses as prescribed, side effects, risk factors and clinician judgement. The safe action is to disclose everything to the prescriber and pharmacist.
Should I reduce opioids before a cannabis appointment?
Do not change opioid dosing because of an article. If opioid treatment needs review, speak to the clinician responsible for that prescription.
What if I use opioids that are not on my NHS record?
Tell the prescriber. That includes private prescriptions, opioid substitution treatment and non-prescribed opioid use. The point is safety, not judgement.
Should I mention alcohol?
Yes. Alcohol can add to sedation and impairment risks with some medicines, and the prescriber needs to know.
Sources
- NHS. Medical cannabis. https://www.nhs.uk/medicines/medical-cannabis/
- NICE. Cannabis-based medicinal products: recommendations, NG144. https://www.nice.org.uk/guidance/ng144/chapter/recommendations
- NHS. Morphine. https://www.nhs.uk/medicines/morphine/
- NHS. Tramadol. https://www.nhs.uk/medicines/tramadol/about-tramadol/
- NHS. Tramadol common questions. https://www.nhs.uk/medicines/tramadol/common-questions-about-tramadol/
- NHS. Buprenorphine for pain common questions. https://www.nhs.uk/medicines/buprenorphine-for-pain/common-questions-about-buprenorphine/
- NHS England. Cannabis-based products for medicinal use. https://www.england.nhs.uk/long-read/cannabis-based-products-for-medicinal-use-cbpms/
- GMC. Information for doctors on cannabis-based products for medicinal use. https://www.gmc-uk.org/professional-standards/learning-materials/information-for-doctors-on-cannabis-based-products-for-medicinal-use
- CQC. Cannabis-based medicinal products: what CQC looks for when registering providers. https://www.cqc.org.uk/guidance-providers/healthcare/cannabis-based-medicinal-products-what-we-look-when-we-register
- GOV.UK. Drug driving law. https://www.gov.uk/drug-driving-law
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