Drug interactions in a sample of inpatients diagnosed with cannabis use disorder

The majority of patients with cannabis use disorder (CUD) regularly take medication. Cannabinoids influence metabolism of some commonly prescribed drugs. However, little is known about the characteristics and frequency of potential cannabis-drug (CDIs) and drug-drug interactions (DDIs) in patients with CUD. Therefore, our study aimed to determine the prevalence and characteristics of drug interactions in patients with CUD during inpatient treatment on an addiction-specific ward over a six-year-period. To this aim, medication charts were analyzed and screened for potential CDIs and DDIs. Herein, the drugs.com classification for potential CDIs and UpToDate Lexicomp program for potential DDIs were utilized. The study cohort consisted of 301 patient cases, predominantly male (85.0%), with a median age of 37 years. 89.4% (269/301) of all cases involved were taking at least one drug that could potentially interact with cannabis. Levomethadone, buprenorphine and morphine were the most common drugs involved in potentially serious CDIs. In addition, 196 DDIs were identified, of which 25.5% were classified as 'avoid combination' and 74.5% as 'consider therapy modification'. Hereby, combinations of levomethadone with other psychotropic drugs most frequently accounted for potentially severe and mild DDIs. The results of our study indicate that especially patients diagnosed with CUD also receiving opioid substitution therapy are at risk for potential drug interactions. Therefore, a clinical monitoring of vigilance and respiratory function should be applied during inpatient treatment. Routine use of interaction check tools in patients diagnosed with CUD should also be considered by healthcare providers. In addition, therapeutic drug monitoring (TDM) should be used to increase medication safety in this patient population.