A study published in the Anales de Pediatria assessed the renal safety of treatment with polyethylene glycol 3350 with electrolytes, at 1, 3 and 6 months, its gastrointestinal tolerance, and dose effectiveness. This study evaluated three groups of 30 healthy patients from 2-10 years of age, having functional constipation (Rome III criteria) with 1, 3 and 6 months of treatment. The mean dose of polyethylene glycol 3350 administered was 0.37g/kg/day titrated according to age, weight, and response. It was found that the number of stools per week during treatment displayed a significant difference (from 2.4±0.64 to 6.21±1.5) post-treatment. In addition, there was a significant improvement in the Bristol scale score. Meanwhile, the mean sodium intake was 112mg (range 4-12mg/kg/day). Moreover, the values of sodium and urine osmolality were normal in all groups with no statistical difference compared to normal control values – from 90 healthy children without treatment. In addition, near-infrared reflectance analysis (NIRA) values were normal in all patients. Furthermore, hydrogen breath test was normal with a median of 7ppm. Hence, it was concluded that owing to its negative adverse renal biochemical parameters or gastrointestinal disorders and optimal tolerance and efficacy, polyethylene glycol 3350 with electrolytes can be safely recommended for the treatment of functional constipation in children in the short and long term.