International forskning

CBD-oil as a potential solution in case of severe tamoxifen-related side effects

Sanne M Buijs 1, C Louwrens Braal 2, Stefan A J Buck 2, Noud F van Maanen 2, Lonneke M van der Meijden-Erkelens 3, Heleen A Kuijper-Tissot van Patot 3, Esther Oomen-de Hoop 2, Lotte Saes 2, Sophia J van den Boogerd 4, Liesbeth E M Struik 5, Quirine C van Rossum-Schornagel 6, Ron H J Mathijssen 2, Stijn L W Koolen 2 7, Agnes Jager 2

  • 1Department of Medical Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
  • 2Department of Medical Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
  • 3Clinical Cannabis Care Pharmacy, Breukelen, the Netherlands.
  • 4Department of Medical Oncology, Alexander Monro Hospital, Bilthoven, The Netherlands.
  • 5Department of Internal Medicine, Ikazia Hospital, Rotterdam, The Netherlands.
  • 6Department of Internal Medicine, Franciscus Gasthuis & Vlietland, Schiedam, The Netherlands.
  • 7Department of Hospital Pharmacy, Erasmus University Medical Center, Rotterdam, The Netherlands.


Tamoxifen may lead to bothersome side effects contributing to non-compliance and decreased quality of life. Patients searching for relief are increasingly turning to cannabinoids such as CBD-oil. However, CBD-oil might affect tamoxifen pharmacokinetics (PK) through CYP2D6 inhibition. The aims of this open-label, single-arm study were (1) to determine the PK profile of tamoxifen when using CBD-oil, and (2) to subsequently investigate whether CBD-oil has a beneficial influence on side effects. Study patients had to have steady-state endoxifen concentrations ≥16 nM (conservative threshold). PK sampling and side effect assessment was done at initiation of CBD-oil and 28 days thereafter. Bio-equivalence could be concluded if the 90% confidence interval (CI) for the difference in endoxifen AUC fell within the [-20%; +25%] interval. The effect of CBD-oil on side effects was evaluated using the FACT-ES questionnaire. Endoxifen AUC decreased after CBD-oil by 12.6% (n = 15, 90% CI -18.7%, -6.1%) but remained within bio-equivalence boundaries. The endocrine sub-scale of the FACT-ES improved clinically relevant with 6.7 points (n = 26, p < 0.001) and health-related quality of life improved with 4.7 points after using CBD (95% CI + 1.8, +7.6). We conclude that CBD-oil, if of good quality and with a dosage below 50 mg, does not have to be discouraged in patients using it for tamoxifen-related side effects.