Medication Summary
A high water intake is an essential measure. A minimum of 6-8 8-oz glasses a day is recommended.
Bulking agents, through the increase of fiber, are also important. Many agents are on the market for this purpose and typically contain psyllium husk or cellulose; each patient may respond differently to each agent. No single agent is superior to another.
Laxatives may be considered and continued if found to be helpful. The best laxatives for this purpose are osmotic agents, such as magnesium salts, sorbitol, or lactulose (the latter two may increase flatulence). Patients need encouragement to take sufficient amounts to produce a result. Stimulant laxatives are best left as a last resort because they may possibly induce deterioration in the ability of the colon to evacuate. Typical stimulant laxatives are senna and bisacodyl-containing medications. Many patients take natural herbal laxatives; these typically contain cascara.
For more information, see the FDA MedWatch Product Safety Alert.
Laxatives
Class Summary
Increase peristalsis of the intestine, reducing the time toxic substances remain in the lower GI tract.
Psyllium (Metamucil, Fiberall)
Promotes bowel evacuation by forming viscous liquid and perhaps by inducing peristalsis.
Magnesium hydroxide (Philips' Milk of Magnesia)
Causes osmotic retention of fluid, which distends the colon and probably increases peristaltic activity; promotes emptying of bowel.
Sorbitol
Hyperosmotic laxative that has cathartic actions in the GI tract.
Lactulose (Cephulac, Cholac, Constilac)
Produces osmotic effect in colon that results in distention and promotes peristalsis.
Senna (Senexon, Ex-Lax, Senokot, Senna-Gen, Black-Draught, Agoral)
Anthraquinone stimulant hydrolyzed by colonic bacteria into active compound. More potent than cascara sagrada and produces considerably more abdominal pain. Usually produces action 8-12 h after administration.
Bisacodyl (Bisac-Evac, Bisco-Lax, Dulcolax, Dacodyl)
Stimulates peristalsis, possibly by stimulating colonic intramural plexus. Alters water and electrolyte secretion, producing net intestinal fluid accumulation and laxation.
Cascara sagrada
Irritates intestinal mucosa, increasing the rate of colonic motility and changes the fluid and electrolyte secretion.
Polyethylene glycol (PEG) solution
For the treatment of occasional constipation. In theory, there is less risk of dehydration or electrolyte imbalance with isotonic polyethylene glycol compared with hypertonic sugar solutions. The laxative effect is generated because polyethylene glycol is not absorbed and continues to hold water by osmotic action through the small bowel and the colon, resulting in mechanical cleansing. Supplied with measuring cap marked to contain 17 g of laxative powder when filled to the indicated line. May require 2-4 d (48-96 h) to produce bowel movement.
