ABSTRACTObjectives: The efficacy and safety of treatments for constipation in severely intellectually disabled patients and their associated cost-effectiveness are an underinvestigated area of clinical practice. Aiming to address this, the objectives of the study were to evaluate the efficacy and tolerability of polyethylene glycol 3350 plus electrolytes (Movicol; PEG+E) by comparing clinical data collected before and after its introduction to a stable population of residents of a mental health care, long-stay institution. The study also attempted an economic evaluation of the use of PEG+E in this setting.* Movicol is a registered trademark of NorgineResearch design and methods: This was a retrospective study of 54/66 severely intellectually and physically disabled residents of a specialist unit at La Milétrie University Hospital, Poitiers, France, who suffered regularly from constipation. A total of 54 residents were treated with PEG+E (1–3 sachets a day) for 24 months. The number of stools, episodes of diarrhoea (defined as frequent stools, not necessarily watery), body weights and blood biochemistry were recorded. Data were compared with those recorded during the 21 months preceding the introduction of PEG+E for 16/54 residents who had been treated regularly with a range of other interventions for the relief of constipation. The monthly use and costs of laxatives, enemas and suppositories was obtained from hospital pharmacy records, and the total hospital costs before and after the introduction of PEG+E treatment was calculated.Results: The mean (± standard deviation) number of stools per patient per month was significantly greater following the introduction of PEG+E (24.9 ± 6.3) compared to before its use (12.4 ± 3.4) ( p < 0.001). The mean (± standard deviation) monthly number of episodes of diarrhoea per patient before and after the introduction of PEG+E was 0.1 ± 0.1 and 6.3 ± 2.9, respectively ( p < 0.001). Treatment with PEG+E was not associated with adverse effects on body weight or blood biochemistry values. Introduction of PEG+E and its increasing use reduced the total hospital medical ward expenditure on laxatives from 3788 to 1767 Euros per month.Conclusions: PEG+E is effective in the clinical management of constipation in an institutional setting. Furthermore, long-term intensive therapy with PEG+E was not associated with adverse effects on body weight or blood biochemistry values. Although the time periods over which the economic data and the efficacy and safety data were collected did not directly correspond, this study indicates that use of PEG+E in the management of constipation in people with severe intellectual disability may be cost-effective, reducing hospital laxative costs.