Chronic constipation: Let symptom type and severity direct treatment

Important points for patients. Counsel patients for whom you recommend fiber intake that it may take several weeks for them to experience relief,^5,8 and that long-term fiber use may cause abdominal distension, bloating, and flatulence.^4,5,8,15 Few serious adverse effects (eg, delayed gastric emptying, anorexia, and iron and calcium malabsorption) are associated with bulking agents; however, fecal impaction may occur in patients with severe colonic inertia.¹⁶

Hypersensitivity reactions have been reported in patients who ingest psyllium and in healthcare workers exposed to it.¹⁶

Osmotic laxatives may help

When increased fiber intake fails to alleviate symptoms of constipation, patients are often prescribed an osmotic laxative (eg, magnesium hydroxide, magnesium citrate, sodium phosphate, or polyethylene glycol [PEG]) (SOR: B), which promotes water secretion in the intestines.^4,8,15 However, several days may pass before the laxatives take effect, and they are indicated only for short-term use in patients with occasional constipation.¹

Common adverse effects include abdominal cramping, bloating, and flatulence.^4,10,17 More serious adverse effects include hypermagnesemia, hyperphosphatemia, hypercalcemia, hyponatremia, hypokalemia, hypovolemia, and diarrhea^1,16 ; the incidences of these events were not reported.

The ACG Task Force gave PEG and lactulose grade A recommendations, based on the quality of evidence supporting their effectiveness at improving stool frequency and stool consistency in patients with chronic constipation.¹ PEG was the only laxative shown in clinical trials to improve bowel movement frequency, stool consistency, and colonic transit time. However, this conclusion was based on analysis of all formulations—PMF-100, PEG 3350, PEG/electrolyte solutions, and high-molecular-weight PEG (PEG 4000); PEG 3350 (Miralax), the only PEG formulation approved by the FDA for use in patients with constipation, is indicated specifically for patients with occasional constipation. The Task Force determined that data were insufficient to make a recommendation for milk of magnesia (ACG grade: B).¹

Stimulant laxatives, if all else fails

Stimulants (eg, bisacodyl, cascara, senna, ricinoleic acid) cause rhythmic muscle contractions in the intestines and increase intestinal motility and secretions.^4,5,9,15,17 Controlled study data for stimulant laxatives are sparse (SOR: B).¹⁸ They work within hours,^12,15,17,19 but use them judiciously.⁹

A common adverse effect is abdominal pain; more serious adverse effects include electrolyte imbalances, allergic reactions, and hepatotoxicity.^1,16,20 However, these effects appear to be no more severe or frequent than effects of other constipation treatments. Long-term use can also cause benign pigmentation changes in the colon (Pseudomelanosis coli) and can lead to reduced colonic motility (colonic inertia).^12,16

Given safety concerns with long-term use, reserve stimulant laxatives for patients who are refractory to or who cannot tolerate other agents.^5,17 You should use them only as needed and for a brief time¹² (the general guideline for most over-the-counter products is 1 week or less). The ACG Task Force concluded that data are insufficient to make recommendations for stimulant laxatives (ACG grade: B).¹

Fiber or laxatives better?

A meta-analysis of randomized clinical trials found that fiber and laxatives increased bowel movement frequency by an overall weighted mean of 1.4 (95% confidence interval, 1.1–1.8) bowel movements per week.²¹ However, evidence was insufficient to establish whether fiber was superior to laxatives or whether one laxative class was superior to another.

Another meta-analysis found that, in studies lasting 4 weeks or less, fiber supplements and laxatives improved stool frequency (mean increase, 1.9 stool/week) and stool weight (mean increase, 476 g) but that these benefits were not clearly distinguishable from those of placebo (stool frequency, 1 stool; stool weight, 434 g).¹⁸

Large, well-designed, comparative trials of treatments for chronic constipation in adults are needed.²² Current literature contains few thoroughly reported studies of fiber and laxative use.¹⁸ Additionally, standardized measures to assess the adverse effects and outcomes (effects on quality of life) of specific agents have rarely been incorporated.^18,22 Given the problematic safety/tolerability profiles of some laxatives, it is unknown whether they improve quality of life of patients with constipation.¹⁸

TABLE
Treatments for chronic constipation