OTCs Today
Daniel L. Krinsky, RPh, MS
Constipation is a common GI complaint usually best managed with a combination of nonpharmacologic and pharmacologic interventions. Older adults (>65 y) are five times more likely to experience constipation than younger adults, and women are more than three times as likely as men to be affected. Primary treatment goals are to relieve constipation and reestablish normal bowel function, to establish dietary and exercise habits to help prevent recurrence, and to promote safe and effective use of laxative products.
It is important to use the QuEST/SCHOLAR-MAC process to obtain an accurate history to determine the likely cause of constipation and treatment options. Initial management of constipation involves making lifestyle changes such as the three “F’s”: increasing intake of high-Fiber foods, increasing Fluid intake, and initiating more Fitness, or regular exercise. The American Dietetic Association recommends an adult daily dietary fiber intake of 25 g for adult women and 38 g for adult men. If dietary modifications are not effective, patients may use a commercially available fiber supplement.
Pharmacologic treatment options
Pharmacologic interventions may be used if more immediate relief is desired. Consider dosage forms, palatability, convenience, time to achieve the desired effect, and administration issues when determining pharmacologic recommendations.Key exclusions for self-treatment are marked abdominal pain, distention, cramping, or flatulence; associated fever, nausea, or vomiting; blood in the stool; age younger than 2 years; and unexplained changes in bowel habits.
Laxatives should be selected on the basis of the patient’s age and health status, along with the product’s mechanism of action. FDA labeling limits laxative use to short-term (<7 d) treatment without medical referral. Proper selection depends on the underlying cause of the constipation and individual patient factors and preferences. Agents are classified by mechanism of action and include bulk-forming, hyperosmotic, emollient, lubricant, saline, and stimulants.
Bulk-forming laxatives are the recommended treatment of choice in most cases of constipation because their effects most closely approximate the body’s physiologic process. The usual time to onset of action for bulk-forming laxatives is 12 to 24 hours, but onset of effect may be delayed up to 72 hours.
Hyperosmotic agents include polyethylene glycol 3350 (PEG 3350) and glycerin. These products contain large, poorly absorbed ions or molecules that draw water into the colon or rectum through osmosis to stimulate a bowel movement. Glycerin suppositories usually produce a bowel movement within 15 to 30 minutes and are safe for use in all approved age groups.
Emollients (stool softeners) such as docusate act in the small and large intestine to increase the wetting efficiency of intestinal fluid, leading to softening of the fecal mass. They are used to prevent straining and painful defecation in patients with anorectal disorders or in those who should avoid straining. Docusate has an onset of action of 12 to 72 hours but may take up to 3 to 5 days to work.
The stimulant laxatives senna and bisacodyl work primarily in the colon to increase intestinal motility. They also increase secretion of water and electrolytes in the intestine. Their time to onset of action is usually 6 to 10 hours after oral administration, but onset of effect may take up to 24 hours. Bisacodyl suppositories usually take effect 15 to 60 minutes after administration.
Drug interactions with nonprescription laxatives usually involve an issue with drug absorption or GI distress; laxatives should not be administered within 2 hours of any other medication. Major hazards of stimulant laxative use are severe cramping, electrolyte and fluid deficiencies, enteric loss of protein, malabsorption caused by excessive hypermotility and catharsis, and hypokalemia.
Counseling tips
Counsel patients on drug and nondrug options, future preventive steps, and when to expect a response. Caution patients that laxative overuse can cause diarrhea and vomiting, fluid and electrolyte losses (especially hypokalemia), and dehydration. Inform them that proper administration of enemas and suppositories is important to achieve desired benefits and to prevent adverse effects.
Populations such as children, pregnant women, and older adults all require special attention because they have unique factors that can affect bowel habits. Please take extra time when interacting with a patient in one of these groups to ensure complete assessment and targeted recommendations.