First-line: nonpharmacological measures (e.g., high-fiber diet, increased fluid intake, and exercise) and/or trial of bulk-forming laxatives
Second-line: step-wise pharmacotherapy with laxatives from other classes
Begin with an osmotic laxative.
If symptoms persist, add a short course of a stimulant laxative.
Laxatives
Bulk-forming laxatives (fiber)
Mechanism
Bulk-forming laxatives are indigestible, not systemically absorbed.
Soluble fibers increase water absorption in the intestinal lumen → stretching of the bowel wall → stimulation of peristalsis
Osmotic laxatives
Agents: Polyethylene glycol (PEG) and lactulose
Stimulant laxatives (secretory laxatives)
Agents: Bisacodyl and sodium picosulfate
Mechanism
Stimulation of epithelial cell secretion of electrolytes into the colonic lumen → ↑ Secretion of fluid into the colon (with bisacodyl, this secretory activity is nitric oxide-mediated)