Kirsten Rock is a PhD student at King’s College London, funded by the SSA. Her research is centred around drug-drug interactions between pharmaceutical medicines and illicit substances with a particular focus on developing strategies to mitigate drug-related harms and prevent future deaths. Prior to starting her PhD, Kirsten worked for the National Programme on Substance Use Mortality, analysing trends in drug-related deaths in the UK. She has presented her research at national and international conferences, and won the prize for best overall student poster at the SSA conference in 2025.

Abstract

Mirtazapine in cocaine-related deaths: Toxicological interaction or differential prescribing and use?

Aims: Cocaine is one of the most commonly used illicit drugs worldwide. Exploratory analysis has revealed that mirtazapine is disproportionately detected in cocaine-related deaths compared to other antidepressants. This study investigated whether this reflected a pharmacological drug–drug interaction or differential prescribing and use patterns.

Methods: A retrospective cross-sectional study was conducted. Cocaine-related deaths concluded to be unintentional and occurred between 2010–2024 in England were extracted from the National Programme on Substance Use Mortality. All data analysis was performed in Python. Ethical approval was not required as all subjects were deceased.

Results: Mirtazapine was one of the most commonly co-detected drugs in cocaine-related deaths (23%,n=2,515/11,088), with a significant increase in co-detections over time (rho=0.83,p=0.01). Toxicological cocaine concentrations were not altered by mirtazapine co-use, indicating no drug–drug interaction. Compared to other antidepressants, there was massively more prescribing of mirtazapine in people who use cocaine (18%; sertraline: 8%; amitriptyline: 6%; citalopram: 4%), alongside increased rates of illicit sourcing (13%; sertraline: 3%; amitriptyline: 6%; citalopram: 2%).

Conclusions: The findings of this study demonstrate a concerning trend of mirtazapine overuse in people who use cocaine. There is a need for open communication between GPs and patients to balance safe prescribing when cocaine use is prevalent. Other harm reduction strategies, such as providing advice on safe drug use, access to drug treatment services, or sleep hygiene, can reduce the harms from mirtazapine-cocaine co-use.