Older Patients, Wiser Care

There's More Than One Way to Cure Constipation

Last updated:

January 20, 2011
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Dear Dr. K.,

What's the best way to treat constipation in an older person? My father has chronic back pain due to arthritis in his spine. Taking a Vicodin tablet three times a day really helps, but it seems to make him constipated. His doctor recommended he take Senna every day, but I've always heard that one shouldn't use laxatives for more than a few days at a time.

Constipation does become more common as people age. So it's unfortunate that all the opiate pain-killers many older adults take (including Vicodin) make constipation worse.

Luckily it's usually easy to find a way to keep the bowels running relatively smoothly, even while taking a transit-slower like Vicodin. And although the packaging of most laxatives implies that one shouldn't use the product chronically, several of them can be used on a very regular basis, without apparent harm to the bowel.

Interestingly, many doctors may have never gotten around to learning the details about laxative options. It's considered a less-than-glamorous topic, after all, and since many products are available over-the-counter (OTC) and generically, drug companies don't provide much doctor education on the well-established laxatives that have good lengthy track records.

Proper treatment of constipation often makes a world of difference to an older person. Here's a list of time-tested bowel-moving options, and how they work:

Osmotic agents: These laxatives contain non-absorbable sugars, which draw more water into the bowel. (The scientific name for this water-moving process is "osmosis.") This makes the stool softer and easier to keep moving. Prune juice works this way, as do the OTC drug MiraLax (polyethylene glycol) and the prescription laxatives lactulose and sorbitol. Liquids such as Golytely, which is used to clean out the colon before colonoscopy, or magnesium citrate, also work in a similar way but are more likely to affect the body's electrolytes. A 2007 study found that polyethylene glycol is safe and effective even when taken every day for six months.

Stimulating agents: These act directly on the colon to stimulate muscle activity. Examples include senna (available OTC) and bisacodyl. (Bisacodyl is also available as a suppository.) They are often prescribed during hospitalizations and in nursing homes. It used to be thought that using bowel stimulants regularly might permanently alter the nerves and muscles in the colon. However, most experts now agree that it seems safe to use these drugs on a daily basis. (Although this hasn't been carefully tested in a research study, many patients have taken these drugs daily for years, with no apparent ill effects on the colon.)

Softening agents: These make the stool a little softer and more slippery. Best-known: docusate (brand name Colace). Although they're probably the most commonly prescribed option, they're, ironically, not very effective. They don't soften the stool nearly as well as an osmotic agent -- and the liquid formulation of docusate tastes truly terrible.

Fiber: So-called "bulking agents" promote bowel movements by "bulking up" the stool; a healthy colon works best when filled with a good amount of roughage that's not packed too hard. It's essential that fiber be taken with plenty of water. If not, or if a person suffers from an aging slower colon, fiber can sometimes paradoxically cause things to get stopped up. The most common supplemental formulation is psyllium powder (brand name Metamucil). It's also not uncommon for fiber supplements to cause gas and bloating. For this reason, geriatricians tend to be cautious about using fiber supplements in those who are very frail, prone to dehydration, or otherwise seem to have slow colons. One can also get fiber more naturally through eating certain cereals, fruits, and vegetables.

Back to your father's situation: Opiate pain-killers such as Vicodin do slow down the bowel. So I usually start by recommending some prunes or prune juice, with 1-2 tablets of senna as well. For those who don't like prunes, MiraLax (polyethylene glycol) is my favorite alternative osmotic agent.

"What about fiber?" families often ask. Well, it's always a good idea to eat a healthy diet with whole grains, fruits, and greens. However, in the case of someone using an opiate painkiller, a fiber supplement probably won't make the constipation better. In fact, unless the fiber is taken with prunes or another laxative that draws water in the stool, it might even make things worse.

My prescription for caregivers about laxatives:

  • Regular use of the laxatives listed above is generally safe. Do be sure to add any laxatives to a person's medication list, and keep doctors in the loop if they're being used.
  • Know that constipation is a nearly universal side effect of opiate painkillers such as Vicodin. Just remember: It's better to use and adjust the laxatives rather than dial back much-needed pain medication.
  • It's generally safe to adjust the dosage a little ways up or down on your own.
  • Many people respond best to a combination of different types of laxatives.
  • Every person's colon is unique. It may take a little experimenting to find the right doses and types of laxatives for a given person. The goal is to have a good-sized soft bowel movement every 1-2 days.