Senna or Magnesium Oxide Relieves Chronic Idiopathic Constipation Symptoms

woman with stomach pain
stomach pain, constipation, indigestion
This randomized, placebo-controlled trial compared the safety and efficacy of senna, a stimulant laxative, vs magnesium oxide, an osmotic agent, to treat chronic idiopathic constipation.

In a randomized, placebo-controlled trial, senna, an anthraquinone stimulant laxative, and magnesium oxide (MgO) were both found to be effective at decreasing symptoms of constipation, according to findings published in Functional GI Disorders.

Researchers from the Hyogo College of Medicine in Nishinomiya, Japan, recruited patients with chronic idiopathic constipation (N=90) from both their hospital and 4 related centers. Patients were selected between March and June 2019 and randomly assigned to receive 1 g/d senna (n=30), 1.5 g/d MgO (n=30), or a placebo (n=30) for 28 days. They asked patients to record their bowel movement frequency and form and to respond to a symptom questionnaire weekly.

The patients were a mean age of 42.2 (±11.2) years, and 93.3% were women. At the study conclusion, no patients were lost; however, 62.2% reduced their doses (senna: 83.3% vs MGO: 53.3%; placebo: 50%; P =.02).

Compared with the placebo group, patients in both treatment groups reported significant improvement of their weekly constipation symptoms (P <.001). Overall symptom improvement was 69.2% among patients in the senna group (P <.0001) and 68.3% among the MgO group (P <.001) compared with 11.7% among the placebo group.

Weekly instance of spontaneous bowel movements and complete spontaneous bowel movements improved among both treatment groups compared with baseline (P <.01). Compared with the placebo group, patients in either treatment cohort had a significant weekly difference for the degree of change to their stool form (P <.01).

Compared with placebo, researchers observed significant improvements for abdominal bloating (placebo: −0.2±0.1 vs senna: −0.9±0.16; P <.05; vs MgO: −1.1±0.16; P <.01), abdominal discomfort (placebo: 0±0.08 vs MgO: −0.8±0.13; P <.01), straining (placebo: −0.1±0.11 vs senna: −1.4±0.08; P <.001; vs MgO: −1.4±0.11; P <.001), and incomplete evacuation sensation (placebo: −0.1±0.13 vs senna: −0.9±0.15; P <.01; vs MgO: −1.1±0.11; P <.05).

Participants in the senna group reported a significant difference of their satisfaction (P <.001) and physical (P <.05) scores, and participants in the MgO group reported significant changes of their scores for physical (P <.01), worry (P <.01), and satisfaction (P <.0001). Constipation scoring system values improved more among the treatment groups (placebo: 1±3.2 vs senna: 4.9±3.2; P <.01; vs MgO: 3.6±3.7; P <.001).

A potential limitation of this study was that the groups had differing dosage schedules. The senna group took 2 capsules twice daily, and the placebo group took 2 capsules once per day. The MgO group took 2 capsules 3 times a day, and the placebo group took 2 capsules 3 times daily. As dosage rates differed among treatment groups, the different schedules and number of pills may have introduced bias.

The study authors concluded that both senna and MgO significantly improved constipation symptoms and alleviated some negative impacts from chronic idiopathic constipation on quality of life.

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Morishita D, Tomita T, Mori S, et al. Senna versus magnesium oxide for the treatment of chronic constipation: a randomized, placebo-controlled trial. Published online September 22, 2020. Am J Gastroenterol. doi: 10.14309/ajg.0000000000000942