Osmotic agents Increase water content in colon to maintain isotonicity with plasma | Polyethylene glycol | 17–34 g/d | Bloating, flatulence, abdominal pain, diarrhea |
Lactulose | 15–30 mL daily to twice daily | Bloating, flatulence, abdominal pain, diarrhea |
Sorbitol | 15–30 mL daily to twice daily | Bloating, flatulence, abdominal pain, diarrhea |
Magnesium hydroxide | 15–30 mg daily to twice daily | Hypermagnesemia, bloating, flatulence, abdominal pain, diarrhea |
Sodium phosphate | 10–25 mL with 350 mL of water | Hyperphosphatemia, hypocalcemia, hypernatremia and hypokalemia, bloating, flatulence, abdominal pain, diarrhea |
Bulk agents Fibre retains water, which increases fecal mass, stimulating peristalsis | Psyllium | Up to 20 g/d | Bloating, flatulence; rarely cases of mechanical obstruction and allergic reactions |
Methylcellulose | Up to 20 g/d | Bloating, flatulence |
Polycarbophil | Up to 20 g/d | Bloating, flatulence |
Stimulants Increase intestinal motility | Sennoside | Up to 68.8 g/d in divided doses | Abdominal cramps, hypokalemia, pseudomelanosis coli |
Bisacodyl | 5–10 mg/d orally or rectally | Abdominal cramps, hypokalemia, pseudomelanosis coli |
Stool softeners Decrease stool surface tension leading to increased water penetration | Dioctyl sodium sulfosuccinate or docusate | 100 mg twice daily | Abdominal cramps, diarrhea |
Docusate calcium | 240 mg twice daily | Abdominal cramps, diarrhea |
Prokinetic agents Stimulates 5-HT4 intestinal receptors, inducing peristalsis | Prucalopride | 2 mg/d | Nausea, vomiting, flatulence, headache |
Enemas or suppositories Enemas distend the rectum to initiate the defecation reflex; they also soften stool | Phosphate-based enema | 120 mL/d | Hyperphosphatemia and other electrolyte disturbances |
Tap-water enema | 500 mL/d | |
Glycerin suppository | Once daily | |