Abstract: We screened 7674 citations, from which 14 trials with 1844 participants met our inclusion criteria. Ten RCTs were placebo-controlled, and four reported comparisons of different drugs. Drugs examined in these trials were the following: antipsychotics (n = 10), alpha2 agonists (n = 3; all dexmedetomidine), statins (n = 2), opioids (n = 1; morphine), serotonin antagonists (n = 1; ondansetron), and cholinesterase (CHE) inhibitors (n = 1; rivastigmine). Only one of these trials consistently used non-pharmacological interventions that are known to improve patient outcomes in both intervention and control groups. Eleven studies (n = 1153 participants) contributed to analysis of the primary outcome. Results of the NMA showed that the intervention with the smallest ratio of means (RoM) (i.e. most preferred) compared with placebo was the alpha2 agonist dexmedetomidine (0.58; 95% credible interval (CrI) 0.26 to 1.27; surface under the cumulative ranking curve (SUCRA) 0.895; moderate-quality evidence). In order of descending SUCRA values (best to worst), the next best interventions were atypical antipsychotics (RoM 0.80, 95% CrI 0.50 to 1.11; SUCRA 0.738; moderate-quality evidence), opioids (RoM 0.88, 95% CrI 0.37 to 2.01; SUCRA 0.578; very-low quality evidence), and typical antipsychotics (RoM 0.96, 95% CrI 0.64 to1.36; SUCRA 0.468; high-quality evidence). The NMAs of multiple secondary outcomes revealed that only the alpha2 agonist dexmedetomidine was associated with a shorter duration of mechanical ventilation (RoM 0.55, 95% CrI 0.34 to 0.89; moderate-quality evidence), and the CHE inhibitor rivastigmine was associated with a longer ICU stay (RoM 2.19, 95% CrI 1.47 to 3.27; moderate-quality evidence). Adverse events often were not reported in these trials or, when reported, were rare; pair-wise analysis of QTc prolongation in seven studies did not show significant differences between antipsychotics, ondansetron, dexmedetomidine, and placebo. We identified trials of varying quality that examined six different drug classes for treatment of delirium in critically ill adults. We found evidence that the alpha2 agonist dexmedetomidine may shorten delirium duration, although this small effect (compared with placebo) was seen in pairwise analyses based on a single study and was not seen in the NMA results. Alpha2 agonists also ranked best for duration of mechanical ventilation and length of ICU stay, whereas the CHE inhibitor rivastigmine was associated with longer ICU stay. We found no evidence of a difference between placebo and any drug in terms of delirium-free and coma-free days, days with coma, physical restraint use, length of stay, long-term cognitive outcomes, or mortality. No studies reported delirium relapse, resolution of symptoms, or quality of life. The ten ongoing studies and the six studies awaiting classification that we identified, once published and assessed, may alter the conclusions of the review.

Plain-language summary: This review is current to 21 March 2019. We found 14 randomized controlled studies that enrolled a total of 1844 adult participants. Six different classes of medicines were tested. These were antipsychotic drugs used as tranquillizers in ten studies; the sedative alpha2 agonist dexmedetomidine in three studies; statins that reduce cholesterol in two studies; opioids as part of pain management in one study; serotonin antagonists for nausea and vomiting in one study; and cholinesterase inhibitors, which are medicines for Alzheimer's disease, in one study. Ten studies compared medicine to placebo - an inactive medicine also known as a sugar pill; four studies compared different drugs. Eleven studies with 1153 participants reported on the main outcome of this review - duration of delirium. When drug classes were directly compared with placebo, only the alpha2 agonist dexmedetomidine was found to reduce the duration of delirium, and the cholinesterase inhibitor rivastigmine was found to prolong the duration of delirium. Each of these results is based on findings from a single small study. The other drugs when compared to placebo did not change delirium duration. The Review authors used the statistical method of network meta-analysis to compare the six different drug classes. Dexmedetomidine was ranked most effective in reducing delirium duration, followed by atypical antipsychotics. However, network meta-analysis of delirium duration failed to rule out the possibility of no difference for all six drug classes compared to placebo. Using this method, we did not find that any drug improved the duration of coma, length of stay, long-term cognitive outcomes, or death. The alpha2 agonist dexmedetomidine shortened time spent on a breathing machine. Adverse events often were not reported in these trials or were rare when reported. An analysis of reported events showed that events were similar to those reported with placebo. We found 10 ongoing studies and six studies awaiting classification that, once published and assessed, may change the conclusions of this review. Most of the included studies were small but of good design. Nine of the 14 studies were considered to have low risk of bias.