Effects of opioids, steroids, benzodiazepines, anticholinergics, and antihistamines on the efficacy of antipsychotics for treating delirium in patients undergoing palliative care

Purpose: To investigate the effects of opioid, steroid, benzodiazepine, anticholinergic, and antihistamine combinations on the efficacy of antipsychotics used to treat delirium. Methods End-of-life palliative care patients with overactive delirium were included. Changes in delirium symptoms were assessed using the Intensive Care Delirium Screening Checklist (ICDSC). Changes in scores before and after antipsychotic use in 97 patients with ICDSC scores of ≥ 4 were retrospectively reviewed from medical records. A mean ICDSC score < 4 for the first 3 days after antipsychotic administration was evaluated as effective. The number of days with a score < 4 during the 3 days was also evaluated as a secondary outcome. The two efficacies were compared with and without opioids, steroids, benzodiazepines, anticholinergics, and concomitant antihistamines. Results The concomitant use of benzodiazepines before and after delirium treatment tended to decrease the efficacy rate of antipsychotics (odds ratio, 0.330; 95% CI: 0.089–1.222; p  = 0.097). The concomitant use of benzodiazepines also showed a trend toward a lower number of days (%) with a score < 4 (13% vs. 24%, p  = 0.061). There was no influence of the concomitant use of opioids, steroids, anticholinergics, or antihistamines observed. Conclusion There may be a few disadvantages to the continued use of opioids, steroids, anticholinergics, and antihistamines after commencing delirium treatment with antipsychotics. However, the continuation of benzodiazepine administration after delirium onset should be carefully considered because of their potential negative influence on the efficacy of delirium treatment.