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OTCs Today

Mary Warner

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), constipation is defined as having fewer than three bowel movements a week; stools that are hard, dry, or lumpy; stools that are difficult or painful to pass; or a feeling that not all stool has passed. It's important to note, however, that people have different bowel movement patterns, and “normal” can vary enormously among patients.

Constipation is common in male and female patients of all ages, although older adults (> 65 years old) are 5 times more likely to experience constipation than younger adults and women are more than 3 times more likely than men to be affected. Untreated constipation can lead to development of hemorrhoids or anal fissures, rectal prolapse, fecal impaction, or other complications, so it's important to address frequent constipation.

Constipation occurs when the colon absorbs too much water from waste, making the stool dry, hard, and difficult to pass. This can be caused by daily habits (inadequate fluid or fiber intake and lack of exercise) or medications (such as antiacids, antidepressants, ACE inhibitors, and calcium channel blockers). Pregnant women are especially prone to constipation because of hormonal changes and compression of the intestines by the growing fetus, which slows the passage of stool.

In some cases, constipation can be indicative of another medical problem. For example, opiate use can lead to chronic constipation and the opioid epidemic has led to an increase in patients seeking relief. In addition, diseases such as Parkinson's disease, multiple sclerosis, irritable bowel syndrome, and diverticulitis/diverticulosis can result in constipation, as can endocrine problems, colorectal cancer, and lazy bowel syndrome.

Treating constipation

The first line of treatment for constipation is to increase fluid and fiber intake and get more exercise. If those daily life adjustments don't work sufficiently, numerous other options are available on the OTC shelf of the pharmacy.

Bulk-forming laxatives such as psyllium seed, methylcellulose, and calcium polycarbophil absorb water to soften stool, increase bulk, and facilitate elimination. They're available as tablets or capsules; powders to be mixed with water or other liquids; and fiber chews, wafers, or gummies, and the safest, most natural treatment for constipation. Relief generally occurs within 12 to 24 hours, but may take up to 72 hours to work. There are few adverse effects, making them a good choice for patients with chronic constipation. However, patients with fluid restrictions should avoid using these laxatives, as should patients using digoxin or warfarin.

Emollient laxatives, or stool softeners, contain anionic surfactants (docusate sodium) that act in the small and large intestine to increase the wetting efficiency of intestinal fluid. They can take 2 to 3 days to generate relief and should only be used on a short-term basis. Although stool softeners can be taken for occasional constipation, they are more often used in combination with a stimulant laxative for opioid-induced constipation.

Saline laxatives, such as magnesium hydroxide, magnesium citrate, and magnesium sulfate, use nonabsorbable magnesium cations to create an osmotic gradient to pull water into the intestine. These laxatives can be quick-acting, providing relief in 30 minutes to an hour when taken orally. Adverse effects of saline laxatives may include abdominal cramping, nausea, vomiting, or dehydration.

Stimulant laxatives, including anthraquinones (senna), diphenylmethanes (biscodyl), and castor oil, stimulate bowel activity and increase secretion of fluids into the bowel. The time to onset of action for senna and bisacodyl is usually 6 to 10 hours after oral administration but may take up to 24 hours. Stimulant laxatives should be used sparingly, as impaired colon function can occur with chronic use.

Hyperosmotic laxatives contain glycerin or polyethylene glycol 3350 (PEG 3350) that draws water into the colon or rectum through osmosis to stimulate bowel movement. These laxatives are supplied as oral capsules or suppositories and can take effect within 30 minutes.

Combination laxatives often contain a stimulant and an emollient (e.g., senna with docusate sodium) or a stimulant and psyllium. Other available combination laxatives include those with psyllium, bisacodyl, or docusate combined with glycerin.

Type Generic name Brand names Possible adverse effects
Bulk-forming Psyllium seed Metamucil, Konsyl Bloating, gas, cramping, or increased constipation if not taken with enough water
Methylcellulose Citrucel
Calcium polycarbophil FiberCon
Emollient Docusate sodium Colace, Surfak Stomach pain, cramping, diarrhea
Saline Magnesium hydroxide Milk of Magnesia Abdominal cramping, nausea, vomiting, or dehydration; electrolyte imbalance with prolonged use
Magnesium citrate Magnesium citrate
Magnesium sulfate Epsom salts
Hyperosmotic PEG3350, glycerin Miralax, Fleet Bloating, abdominal discomfort, cramping, and flatulence
Stimulants Senna, biscodyl, castor oil Dulcolax, Senokot, Ex-Lax, Correctol Belching, cramping, diarrhea, or nausea; urine discoloration with senna derivatives
Combination products Senna plus docusate sodium Senokot-S Based on stimulant used

Special populations

Children and pregnant/lactating patients should not take laxatives without first trying nonpharmacologic treatement (diet, exercise) and consulting with a pharmacist or physician.

Constipation in children should first be treated by increasing fluid and dietary fiber intake. If further treatment is needed, glycerin suppositories, docusate sodium, and magnesium hydroxide are approved for children 2 to 6 years old. For children 6 to 12 years old, glycerin or bisacodyl suppositories or bulk-forming laxatives, docusate or magnesium hydroxide should be used first, reserving oral stimulate laxatives for use only when other treatments fail.

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Constipation affects up to one-third of patients throughout pregnancy and the postpartum period, primarily caused by compression of the colon by the growing uterus, increasing progesterone levels, low fluid and fiber intake, and the constipating effects of iron and calcium in prenatal supplements.

When increasing fiber and fluids aren't effective at relieving constipation, bulk-forming laxatives should be considered first, along with docusate for those with primarily dry, hard stools. When needed, short-term use of senna or bisacodyl is considered a low-risk approach in pregnancy, as is PEG 3350, though less information is available on the use of PEG 3350 during pregnancy.

Some laxatives, including castor oil, mineral oil, and saline laxatives, should be used cautiously or avoided for pregnant patients. Specific risks have been recognized with use in pregnancy, so such products should be used only very cautiously or perhaps avoided altogether in this setting.

Castor oil has been associated with uterine contraction and rupture, mineral oil may impair absorption of fat-soluble vitamins, and high doses or long-term use of saline laxatives may cause electrolyte imbalances.

Laxatives also may be used postpartum to reestablish normal bowel function. Senna, bisacodyl, PEG 3350, and docusate have a low risk of adverse effects when used by breastfeeding patients. However, castor oil and mineral oil should be avoided during breastfeeding.

What to tell your patients

To avoid constipation, patients should include plenty of fiber and water in their diet and avoid caffeine-containing drinks that can lead to dehydration.

Advise patients to exercise regularly and not to wait if they feel the urge to move their bowels. Patients should understand that excessive laxative use can lead to acute-onset episodes of diarrhea and vomiting, fluid and electrolyte losses (especially hypokalemia), and dehydration.

If patients see blood in the stool, are losing weight unintentionally, have severe abdominal pain, or constipation has lasted more than 3 weeks, they should see a physician to rule out medication- or disease-related causes.

For more information on laxatives, including treatment for special populations and medication interactions, see chapter 15 of APhA's Handbook of Nonprescription Drugs, available in print or online on



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