Patient concerns regarding antidepressant drug-drug interactions: A retrospective analysis using data from a medicines call centre

Introduction: Antidepressant use has increased over the last two decades, with Australia and New Zealand among the highest antidepressant users in Organisation for Economic Co-operation and Development (OECD) countries. Comorbidity and polypharmacy are common in antidepressant users, increasing the likelihood of interaction-related adverse drug events, which are frequently preventable. Aim: We aimed to identify, profile, and analyse potential antidepressant drug-drug interactions in information-seeking antidepressant users. Methods: We retrospectively analysed antidepressant-related drug-drug interaction enquiries from patients or carers who contacted a pharmacist-led Australian national medicines call centre over an 8-year period to determine patient characteristics, concomitant drugs involved, prevalence and type of antidepressant-related drug-drug interaction across life stages, and associated risks. Results: Of 3899 antidepressant drug-drug interaction calls, the most frequent concomitant drugs were antipsychotics, opioids, benzodiazepines, and complementary medicines. Narrative analyses of 2011 calls identified 81.0% of patients with potential drug-drug interactions and 10.4% categorised with worrying symptoms. The most frequent drug-drug interaction risks were excessive sedation, increased anticholinergic effects, serotonin syndrome, and suicidal thoughts. Carers of children aged <15 years and older adults (65-74 years) were more likely to report experiencing worrying symptoms. Although more potential pharmacodynamic than pharmacokinetic interactions were recorded, pharmacokinetic interactions tended to have more significant clinical impact. Discussion: Antidepressant users often have information gaps and safety concerns regarding drug-drug interactions that motivate help-seeking behaviour. Symptoms and drug-drug interaction consequences may be underestimated in these patients. Primary care health professionals have a role in proactively addressing the risk of drug-drug interactions to support benefit-risk assessment and shared decision-making.