A systematic review of laxative use in critically unwell patients: Are we doing more harm than good?

INTRODUCTION: Diarrhoea is common in critically unwell patients and is associated with prolonged intensive care unit (ICU) stay and increased mortality. Its causes are multifactorial; however, emerging evidence suggests that laxative exposure may be an important, and potentially modifiable, contributor. Laxatives are frequently prescribed in ICU patients to prevent constipation, increasingly as part of bowel management protocols (BMP) and care bundles, despite limited supporting evidence. This systematic review evaluated the effects and prevailing associations of laxatives on clinical outcomes in critically unwell adults. METHODS: A systematic literature search of MEDLINE (including PubMed), EMBASE, CENTRAL, CINAHL and ClinicalTrials.gov databases was conducted on 21st July 2026 to review studies that included data on the impact of laxatives on clinical outcomes in critically unwell adult patients. Non-English studies, conference abstracts and studies with paediatric patients or adult patients not admitted to ICU were excluded. Two reviewers independently screened studies and extracted data. Methodological quality and risk of bias were assessed using the ROBINS-I V2 tool for observational studies and RoB 2 for randomised trials. Owing to substantial clinical and methodological heterogeneity, findings were synthesised narratively. RESULTS: The systematic literature search identified 28 studies suitable for review inclusion. Of these, 27 were full-text articles, comprising 21 observational studies and six randomised trials; the remaining study was a meta-analysis. CONCLUSIONS: Despite their frequency, diarrhoea and constipation in critically unwell patients lack clear, consensus definitions. Evidence supporting prophylactic laxative use is limited; studies have not demonstrated consistent improvements in clinically meaningful outcomes and suggest that prophylactic use may contribute to ICU-associated diarrhoea. Although therapeutic laxative use induces defecation, the optimal agent, dose, timing and patient selection remain uncertain. Standardised definitions of bowel dysfunction and high-quality randomised trials are needed to determine the effects of specific laxative strategies on clinical outcomes and diarrhoea incidence in critically unwell patients.