Multimorbidity and Polypharmacy in Psychosis: Identifying Potentially Significant Drug Interactions in an Old Age Inpatient Psychiatry Setting

Abstract

Aims. To determine potentially significant drug interactions in an old age setting among inpatients with psychosis and medical comorbidities over the past 12 months Methods. Study setting: old age inpatient functional ward Sample size: 11 Inclusion criteria: • Inpatients on psychotropic medications with diagnosis ranging from F20 to F29 (ICD-10) • Comorbid chronic medical condition(s) requiring long term drug treatment Exclusion criteria: • Patients with other/co-existing mental health diagnosis excluded • Antibiotics , OTC medications, herbal treatments, emergency treatments and other medications requiring short-term administration excluded from analysis Study tools: • Lexicomp® interaction checker • Category X: Avoid combination • Category D: Consider therapy modification • Further categories (In order of decreasing risk ratings: C, B, A) excluded from the analysis Results. Out of the total 67 inpatients admitted between January 2022 and December 2022, 17 patients had diagnosis ranging between F20 and F29. 4 patients were excluded due to no medical comorbidities and 2 were excluded due to lack of data. Among the 11 patients included in the analysis, the most common medical comorbidities were, in decreasing order, hypertension, hypercholesterolemia and chronic pain. A total of 114 interactions were noted between psychotropic medications and other physical health medications, as follows: No significant interactions: (category A, B, C): 103 Category D (consider therapy modification): 10 • 7 of these interactions were associated with administering Buprenorphine with other medications (Flupentixol, Gabapentin, Nortriptyline, Olanzapine, Amisulpride, Aripiprazole and Pregabalin) leading to additive CNS depressant effects. • Interaction of codeine with Valproate and Flupentixol carried risk of CNS depression. • Carbamazepine interacted with Risperidone via CYP enzyme induction. Category X (avoid combination): 1 • The interaction between Flupentixol and Glycopyrronium was associated with risk of severe anticholinergic effects Conclusion. This study is a preliminary investigation towards understanding the drug interactions in a population with long term mental health and physical health ailments. Awareness regarding the potential interactions can help avoid combinations with possible detrimental effects. The limitations of this study, in terms of sample size and quality of available data, can be overcome by conducting a planned study on a larger population.