Which OTC laxative is most effective for chronic constipation?

Among over-the-counter (OTC) therapies available, only polyethylene glycol (PEG) and senna have level I evidence and grade A recommendations for the treatment of chronic constipation, results of a systematic review have shown. However, only PEG is supported by both short- and long-term studies.

Other OTC therapies with grade B recommendation include psyllium, SupraFiber, magnesium-rich water, magnesium oxide, diphenylmethane stimulants (bisacodyl and sodium picosulfate), fruit-based laxatives (kiwi, mango, prunes, and ficus), and yogurt plus galacto-oligosaccharide, prunes, and linseed oil. Evidence is insufficient for polydextrose, inulin, and fructo-oligosaccharide.

“For these and other alternative products, there is a clear need for more rigorous, high-quality studies using standardized endpoints,” the researchers said. “Docusate lacks well-controlled trials demonstrating its efficacy and has poor evidence to support its use in clinical practice.”

The databases of PubMed and Embase were searched for randomized controlled trials of ≥4-week duration evaluating OTC preparations between 2004 and 2020. The US Preventive Services Task Force criteria (0–5 scale) including randomization, blinding, and withdrawals were used to score the studies.

The researchers then assessed the strengths of evidence within each therapeutic category and graded the recommendations (A, B, C, D, and I) based on the level of evidence (level I, good; II, fair; III, poor).

A total of 1,297 studies were identified, of which 41 were eligible for review. Use of the osmotic laxative PEG and the stimulant senna was backed by good evidence (grade A recommendation). [Am J Gastroenterol 2021;116:1156-1181]

Additionally, moderate evidence (grade B) supported the use of psyllium, SupraFiber, magnesium salts, stimulants (bisacodyl and sodium picosulfate), fruit-based laxatives (kiwi, mango, prunes, and ficus), and yogurt with galacto-oligosaccharide/prunes/linseed oil. In contrast, polydextrose, inulin, and fructo-oligosaccharide had insufficient evidence (grade I).

Common adverse events associated with these OTC therapies included diarrhoea, nausea, bloating, and abdominal pain. No serious adverse events were reported.

“PEG is highly effective with similar or superior efficacy to other OTC and prescription therapies and is well tolerated with long-term administration,” the researchers said.

“In comparison studies, adverse events associated with PEG were similar in pattern and frequency to those of lactulose and tegaserod and lower in frequency compared with prucalopride and naloxegol,” they added. [J Nutr Health Aging 2017;21:429-439; United Eur Gastroenterol J 2020;8:923-932; Am J Gastroenterol 2007;102:1964-1971; Aliment Pharmacol Ther 2013;37:876-886; Am J Gastroenterol 2019;114:954-963]

The present study had certain limitations, such as the inclusion of studies published in the English language only and the exclusion of those with <4 weeks’ duration.

“The spectrum of OTC products has increased, and quality of evidence has improved, but methodological issues including variability in study design, primary outcome measures, trial duration, and small sample sizes remain,” the researchers noted.

“We found good evidence to recommend polyethylene glycol or senna as first-line laxatives and moderate evidence supporting fibre supplements, fruits, stimulant laxatives, and magnesium-based products. For others, further validation with more rigorously designed studies is warranted,” they said.