Association Between Medical Marijuana Cardholder Status and Antiemetic Overuse.

Introduction: The conscientious prescribing of antiemetics by chemotherapy-induced nausea and vomiting (CINV) risk was highlighted in the American Society of Clinical Oncology (ASCO) "Choosing Wisely" recommendations. The pharmacologic properties of medical marijuana (MMJ) may allow for decreased incidence of CINV; however, little is known about the effects of MMJ on the use of antiemetics. This study aimed to determine if MMJ cardholder status, which enables access to MMJ, is associated with antiemetic overuse among patients with cancer. Materials and Methods: This population-based secondary data analysis examined a retrospective cohort derived from the linked Arkansas All Payers Claims Database (2013-2020) and MMJ cardholder registry (2013-2019). The cohort consisted of 20,558 patients with cancer aged 18 and older with a chemotherapy claim in an outpatient setting within 12 months of a cancer diagnosis. Exposure was a registration to receive an MMJ card that permitted access to MMJ. The primary outcome of interest was antiemetic overuse, as characterized by the ASCO recommendation. Antiemetic use associated with chemotherapy was identified through filled prescriptions and medical claims. Multivariable logistic regression, adjusted for baseline demographic and prescription characteristics, was used to calculate the adjusted odds ratios (aOR) of antiemetic overuse among MMJ cardholders compared with non-MMJ cardholders. Results: Among 20,558 eligible patients, 436 (2.1%) had an MMJ card at some point in the study period. Antiemetic overuse was identified in 7.5% of chemotherapy cycles. Compared with non-MMJ cardholders, MMJ cardholders were less likely to experience antiemetics overuse (aOR: 0.76, p < 0.001). Patients with fewer chemotherapy cycles and younger in age had higher odds of antiemetic overuse compared with those with more chemotherapy cycles. The risk of antiemetic overuse did not differ based on gender and rurality of residency. Route of chemotherapy administration, CINV risk category, and type of cancer also impacted the odds of antiemetic overuse. Discussion: The findings indicate that MMJ cardholders are significantly less likely to experience antiemetic overuse than non-MMJ cardholders. Further investigation into the use, effectiveness, and safety of cannabis for CINV mitigation is needed to inform patient and provider decision-making.