Adverse Event Reporting for Cannabis Prescribers in the UK

The UK Yellow Card Scheme and Cannabis

• The MHRA Yellow Card Scheme is the UK’s national pharmacovigilance system for reporting adverse drug reactions
• All healthcare professionals, including private specialist prescribers, are legally and ethically required to report serious adverse events
• Cannabis-specific Yellow Cards can be submitted online at yellowcard.mhra.gov.uk or via the Yellow Card app
• Reports contribute to national safety data and may trigger regulatory action, product alerts, or formulary guidance updates

Adverse event reporting is a professional obligation for all cannabis prescribers, not an optional quality improvement activity. The MHRA relies on clinician and patient reports to identify safety signals for medications that do not have the extensive pre-market safety databases of pharmaceutical drugs. Cannabis-based medicines, many of which are unlicensed in the UK, depend especially heavily on post-market surveillance through the Yellow Card Scheme.

What Constitutes an Adverse Event in Cannabis Prescribing

• Any unexpected side effect, regardless of severity, should be documented in the patient record
• Serious adverse events: hospitalisation, significant disability, congenital anomaly, or death — must be reported to MHRA
• Drug interactions identified in practice should be reported even if the interaction was theoretically predictable
• Product quality concerns (mislabelled cannabinoid content, contamination) should be reported to both MHRA and the supplier

Prescribers must resist the temptation to dismiss adverse events as “patient error” or “exceeding the prescribed dose.” A thorough adverse event record should document the product (with batch number), dose, timing of onset, clinical features, management, and outcome. This level of documentation supports Yellow Card reporting, informs prescribing decisions for future patients, and protects the prescriber if a complaint or clinical negligence claim arises.

Internal Adverse Event Management Within a Cannabis Clinic

• Each clinic should have a written adverse event policy covering detection, documentation, management, and reporting
• A designated clinical governance lead should review serious adverse events and identify any systemic issues
• Regular adverse event review meetings should be held as part of quality assurance activities
• Anonymised aggregated data should be shared with the clinic’s clinical advisory board to drive safety improvements

Well-run cannabis clinics treat adverse event management as a clinical governance priority rather than a compliance box-ticking exercise. A culture where prescribers are encouraged to report and discuss adverse events honestly, without fear of blame, produces better safety outcomes and stronger evidence for the field. Prescribers who encounter unusual or serious adverse events should also consider publishing case reports to disseminate learning to the wider clinical community.

Patient Role in Adverse Event Reporting

• Patients can submit their own Yellow Cards independently or alongside their prescriber’s report
• Provide patients with written guidance on how to recognise and report adverse events at the IMC
• Encourage patients to contact the clinic directly at the first sign of concerning symptoms before waiting for their next appointment
• Include adverse event reporting information in patient-facing materials and clinic websites

Empowering patients to participate in adverse event reporting is both ethically appropriate and practically valuable. Patients often notice and experience adverse effects between clinical appointments, and a system that relies solely on clinician reporting will undercount real-world adverse events. Patient-reported outcomes and adverse event data together provide the most comprehensive picture of cannabis safety in practice.