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Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Generic drug name: methylcellulose (meth ill SELL you loas)
Brand name(s): CITRUCEL
GENERIC: available FAMILY: Drugs for Constipation
Find the drug label by searching at DailyMed.

Generic drug name: psyllium (SILL i yum)
Brand name(s): METAMUCIL, PERDIEM
GENERIC: available FAMILY: Drugs for Constipation
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

There is no information in the drug labels. Consult with your doctor or pharmacist.

Facts About This Drug [top]

Psyllium and methylcellulose for constipation

Psyllium and methylcellulose are laxatives that work by absorbing water and softening the stools in your intestine. The increased stool bulk stimulates the intestines to contract. Fiber that you get from food works exactly the same way. Because a diet high in fiber, combined with plenty of nonalcoholic liquids, has the same effect as psyllium and methylcellulose, it is not usually necessary to use these drugs. Eating high-fiber foods is...

Psyllium and methylcellulose for constipation

Psyllium and methylcellulose are laxatives that work by absorbing water and softening the stools in your intestine. The increased stool bulk stimulates the intestines to contract. Fiber that you get from food works exactly the same way. Because a diet high in fiber, combined with plenty of nonalcoholic liquids, has the same effect as psyllium and methylcellulose, it is not usually necessary to use these drugs. Eating high-fiber foods is preferable to taking psyllium or methylcellulose because these foods give you essential nutrients in addition to fiber. Psyllium and methylcellulose appear to be approximately equally effective.[1] Patients taking psyllium or methylcellulose appear to be less likely to pass gas than when taking another effective laxative, lactulose (CEPHULAC, CHRONOLAC).[2]

When do you really need to take a laxative? You should not take a laxative to “clean out your system” or to make your body act more “normally.” It is untrue that everyone must have a bowel movement daily. Perfectly healthy people may have from three bowel movements per week to three bowel movements per day.

If the frequency of your bowel movements has decreased, if you are having bowel movements less than three times a week, or if you are having difficulty in passing stools, you are constipated, but this does not mean that you need a laxative. It is better to treat simple, occasional constipation without drugs, by eating a high-fiber diet that includes whole-grain breads and cereals, raw vegetables, raw and dried fruits, and beans, and by drinking plenty of nonalcoholic liquids (six to eight glasses per day). This type of diet will both prevent and treat constipation, and it is less costly than taking drugs. Regular exercise—at least 30 minutes per day of swimming, cycling, jogging, or brisk walking—will also help your body maintain regularity.

If you are constipated while traveling or at some other time when it is hard for you to eat properly, it may be appropriate to take a laxative for a short time. The only types of laxatives you should use for self-medication are bulk-forming laxatives such as psyllium or methylcellulose or a hyperosmotic laxative such as lactulose. Bulk-forming laxatives usually take effect in 12 hours to three days, compared with docusate (COLACE, SURFAK), which takes effect one or two days after the first dose but may require three to five days of treatment. Even bulk-forming laxatives should only be used occasionally, if possible.

If you are on a special diet such as a low-salt or low-sugar diet, ask your doctor or pharmacist to help you choose a laxative without ingredients you are trying to avoid. Some laxatives contain sugar (up to half of the product), salt (up to 250 milligrams per dose), or the artificial sweetener NutraSweet.

Psyllium and Cholesterol

When added to the diet, psyllium is a safe, effective method of lowering cholesterol. If cholesterol remains high despite diet, add 10 grams of psyllium a day. Numerous studies have shown that five grams of psyllium twice a day can significantly lower total cholesterol and LDL cholesterol.[3] Psyllium, a naturally occurring vegetable fiber, is clearly safer than any of the cholesterol-lowering drugs. Because psyllium is a laxative that can cause dependence, discontinuing its use may result in a period of several days during which normal bowel movements do not occur.[4]

Allergies to Psyllium

Psyllium has been implicated in severe allergic reactions, typically by inhalation or by ingestion after exposure in the health care setting.[5]

Before You Use This Drug [top]

Tell your doctor if you have or have had:

  • severe abdominal pain
  • allergies to drugs
  • phenylketonuria (if you take the sugarless form)
  • appendicitis
  • colostomy
  • diabetes
  • heart disease
  • high blood pressure
  • hypertension
  • ileostomy
  • impacted bowel movement
  • congestive heart failure
  • intestinal obstruction
  • kidney problems
  • occupational exposure to psyllium
  • rectal bleeding
  • difficulty swallowing

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products.

When You Use This Drug [top]

  • Check with your doctor to make certain your fluid intake is adequate and appropriate (e.g., four to six 8-ounce glasses of fluid daily). If you do not get enough fluids, the laxative will not work properly and may dry and harden, clogging the intestine.[6] This is especially true during hot weather or strenuous exercise. Exercise regularly, such as walking.
  • Avoid alcohol and medications that may cause constipation.
  • Do not use other laxatives while on psyllium or methylcellulose.
  • Do not use unnecessarily (for a cold, tonic, or clean system).
  • When using these drugs to treat constipation, wait at least two days without a bowel movement before considering use.
  • Check with your doctor if a sudden change lasts more than two weeks.
  • Avoid a laxative habit, except if directed by your doctor as part of a cholesterol-lowering regimen. Overuse or extended use may cause dependence.[4]
  • Do not take within two hours of taking other medicines.
  • Check with your doctor if you develop a skin rash.
  • Caution diabetics: Psyllium contains 3.5 grams of dextrose.
  • Do not use these drugs to treat constipation for more than one week. If you have used psyllium or methylcellulose for a week, stop taking it to see if a high-fiber diet and liquids alone will work. If your constipation continues for longer than a week, call your doctor.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Follow manufacturer’s package directions.
  • Drink six to eight full glasses of water each day when using any laxative.
  • Take each dose with a full glass (eight ounces) of water or juice. Mix well.
  • If you take any other drugs, take them at least two hours before or after the time you take psyllium.
  • Do not expose to heat, moisture, or strong light. Keep out of reach of children.

Interactions with Other Drugs [top]

Evaluations of Drug Interactions 2003 lists no drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods as causing “highly clinically significant” or “clinically significant” interactions when used together with the drugs in this section. We also found no interactions in the drugs’ FDA-approved professional package inserts. However, as the number of new drugs approved for marketing increases and as more experience is gained with these drugs over time, new interactions may be discovered.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • breathing difficulty
  • intestinal obstruction (cramping, bloating, nausea)
  • skin rash or itching
  • swallowing difficulty

Call your doctor if you continue to experience:

  • stomach and/or intestinal cramping

last reviewed March 31, 2021