Effectiveness and safety of the co‐administration of Yokukan‐San (Japanese herbal medicine) with antipsychotics in hospitalized older patients with pneumonia

Behavioral and psychological symptoms and delirium frequently occur in hospitalized older patients with pneumonia and are associated with longer hospital stays. Yokukan-San (YKS, traditional Japanese [Kampo] medicine) and antipsychotics are often used to treat delirium and behavioral and psychological symptoms in Japan. Hence, this study aimed to assess the effectiveness and safety of the co-administration of YKS with atypical antipsychotics in older patients with pneumonia.We used the Japanese Diagnosis Procedure Combination inpatient database to retrospectively identify older patients (≥65 years) hospitalized for pneumonia who received antipsychotics within 3 days of hospitalization. The patients were divided into two groups: those who received atypical antipsychotics alone (control group) and those who received both atypical antipsychotics and YKS (YKS group). We compared length of hospital stay, in-hospital mortality, bone fractures, and administration of potassium products between the two groups using propensity score overlap weighting.We identified 4789 patients in the YKS group and 61 641 in the control group. After propensity score overlap weighting, length of hospital stay was statistically significantly shorter in the YKS group (percentage difference -3.0%; 95% confidence interval -5.8% to -0.3%). The proportion of patients who received potassium products was higher in the YKS group (odds ratio 1.34; 95% confidence interval 1.15-1.55). In-hospital death and bone fractures were not significantly different.Co-administration of YKS with atypical antipsychotics could be a reasonable treatment option for hospitalized older patients with pneumonia and aggressive psychiatric symptoms. Geriatr Gerontol Int 2023; 23: 849-854.