Which laxative should I take for my constipation?

DEAR DOCTOR K:

There are so many laxatives on the market. Which one should I take for my constipation?

DEAR READER:

Anyone suffering from constipation should start by boosting fiber and fluid intake. That may do the trick, and you may not need a laxative. If you are age 50 years or younger, the target is 38 grams of fiber per day for men and 25 grams per day for women. For men and women over 50, aim for 30 and 21 grams per day, respectively.

Whole-grain foods, brans, fruits and vegetables are good sources of fiber. When introducing fiber to your diet (or fiber supplements, as I discuss below), do so gradually. Too much, too fast can cause gas, cramping and bloating.

Drink lots of water or other liquids. It’s important to get enough exercise, which also promotes regularity. The way I explain it to my patients is that when you exercise, you “joggle the stuff in your intestines around and loosen it up.” (I don’t believe that this has been scientifically established — perhaps because most scientists have better things to do.)

If these measures fail, laxatives can help ease the passage of stool through the bowel. Following is a list of different types of oral laxatives, along with a few examples of each. They work in a variety of ways; you can see which type best fits your needs.

BULK-FORMING AGENTS: These fiber-based products take a day or so to work. They are very effective and safe to take indefinitely, every day. Take them with plenty of liquid. The most widely used are:

  • wheat dextrin (Benefiber)
  • bran (in food and supplements)
  • calcium polycarbophil (FiberCon)
  • methylcellulose (Citrucel)
  • psyllium (Metamucil)

STOOL SOFTENERS combine with feces to soften the consistency of stool:

  • Docusate (Colace, Surfak) is generally safe for long-term use.
  • Mineral oil should not be used every day because it reduces absorption of fat-soluble vitamins.

OSMOTIC AGENTS promote secretion of water into the colon. They are reasonably safe, even for long-term use. The most widely used is polyethylene glycol (Miralax), which has been shown to help children with functional constipation.

SALINE LAXATIVES attract and retain water in the intestines. This increases pressure and release of stool. The most widely used are various preparations of magnesium (milk of magnesia, Epsom salt).

STIMULANT LAXATIVES act directly on the intestine to promote more vigorous contractions of the colon. They also increase secretion of water in the intestine. They’re best used for occasional constipation, not on a daily basis:

  • bisacodyl (Dulcolax, Correctol)
  • casanthranol (Peri-Colace)
  • cascara (Naturalax)
  • castor oil (Purge)
  • senna (Ex-Lax, Senokot)

CHLORIDE-CHANNEL AGONISTS cause additional fluid to be secreted into the intestine, making it easier to pass stool. This prescription medication — called lubiprostone (Amitiza) — is intended for adults with persistent severe constipation who have not responded to other therapies.