Background: Delirium is a common disorder among hospitalized older patients and results in increased morbidity and mortality. The prevention of delirium is still challenging in older patient care. The role of antipsychotics in delirium prevention has been limited. Therefore, we conducted a trial to investigate the efficacy of quetiapine use to prevent delirium in hospitalized older medical patients.

Methods: This study was a randomized double-blind controlled trial conducted at Ramathibodi Hospital, Bangkok, Thailand. Patients aged ≥65 years hospitalized in the internal medicine service were randomized to quetiapine 12.5 mg or placebo once daily at bedtime for a maximum 7-day duration. The primary end point was delirium incidence. Secondary end points were delirium duration, length of hospital stay, ICU admission, rehospitalization and mortality within 30 and 90 days.

Results: A total of 122 patients were enrolled in the study. Eight (6.6%) left the trial before receiving the first dose of the intervention, whereas 114 (93.4%) were included in an intention-to-treat analysis allocated to the quetiapine or placebo group (n = 57 each). The delirium incidence rates in the quetiapine and placebo groups were 14.0 and 8.8% (OR = 1.698, 95% CI 0.520-5.545, P = 0.381), respectively. Other endpoints in the quetiapine and placebo groups were the median length of hospital stay, 6 (4-8) days versus 5 (4-8) days (P = 0.133), respectively; delirium duration, 4 (2.3-6.5) versus 3 (1.5-4.0) days (P = 0.557), respectively; ICU admission, 3 (5.3%) patients from both groups (P = 1.000); and mortality in the quetiapine and placebo groups, 1 (1.8%) versus 2 (3.5%) at 30 days (P = 0.566) and 7 (12.3%) versus 9 (15.8%) days at 90 days (P = 0.591). There were no significant differences in other outcomes. None of the participants reported adverse events.

Conclusions: Quetiapine prophylaxis did not reduce delirium incidence in hospitalized older medical patients. The use of quetiapine to prevent delirium in this population group should not be recommended.

Trial registration: This trial was retrospectively registered with the Thai clinical trials registry (TCTR) at clinicaltrials.in.th (TCTR20190927001) on September 26, 2019.