What Are Bulk-Forming Laxatives?

Medically reviewed by Nancy Choi, MD on November 20, 2017Written by Annette McDermott on September 29, 2015

Overview

You can’t watch television without seeing commercials marketing products that relieve constipation. Many of these products are bulk-forming laxatives. If you’re thinking about using one to ease symptoms of irregularity, there are some things you should know.

Bulk-forming laxatives absorb liquid in the intestines. This creates a bulky, more liquid-like stool that’s softer and easier to pass. Common bulk-forming laxatives include psyllium (Metamucil), polycarbophil (FiberCon), and methylcellulose (Citrucel).

Other types of laxatives include:

Bulk-forming laxatives are different from these laxatives. They’re most similar to stool softeners in that they help the bowels retain water. Unlike stimulant laxatives, they don’t stimulate nerves that speed up the movement of bowels through the intestines. They also don’t lubricate the stools like lubricant laxatives do. Osmotic laxatives differs from bulk-forming types by helping the intestines — not the bowels — retain water.

Benefits of bulk-forming laxatives

A bulk-forming laxative may help if you experience chronic constipation due to diet, lifestyle, recent surgery, or medication.

Some people prefer bulk-forming laxatives because there’s usually a more gradual improvement of constipation symptoms. They’re often the first line of defense before stimulant or other types of laxatives are used. There’s also less risk of the cramping or explosive diarrhea that could occur with stimulant laxatives.

Laxatives may be beneficial:

  • during pregnancy or for a few days after birth
  • during preparation for surgery
  • in treating constipation in bedridden people
  • in treating constipation caused by medication
  • in preventing strain after surgery
  • in restoring normal bowel function after a period of poor eating or physical inactivity
  • in helping to reduce cholesterol
  • in treating diarrhea

Bulk-forming laxatives may also improve medical conditions made worse by straining, such as:

Side effects of bulk-forming laxatives

Bulk-forming laxatives are generally safe for healthy people. However, side effects or drug interactions may occur, including:

You may also experience mild stomach pain, bloating, or gas.

Some people may have an allergic reaction to psyllium. Call your doctor right away if you experience:

  • difficulty breathing or swallowing
  • itching with a new rash
  • stomach pain
  • nausea
  • vomiting

Take bulk-forming laxatives with at least 8 ounces of water or fruit juice. This will help prevent bowel obstruction. A second glass of water or juice may help prevent additional side effects. Be sure to follow the dosage instructions on the label. During the day, it’s important to stay well-hydrated.

You should begin to feel relief within 12 hours to 3 days.

Precautions

Avoid bulk-forming laxatives and consult your doctor if any of the following apply:

  • You have symptoms of appendicitis or inflamed bowel. These include:
  • You miss a bowel movement for more than two days and have abdominal pain.
  • You develop a rash.
  • You experience a sudden change in bowel habits or function lasting two weeks or more.
  • You’ve taken medication within the last two hours.

Tell your doctor before using bulk-forming laxatives if you have:

People with kidney disease or diabetes are at risk of electrolyte imbalances when taking laxatives. Although your risk may be lower with bulk-forming laxatives, you should still consult your doctor before use if you have either condition.

Laxatives may impact how your body absorbs medications. As a result, you shouldn’t take any medication within two hours of taking a laxative. In addition, you shouldn’t mix oral and rectal laxatives.

The takeaway

When constipation strikes, it’s nice to know help in the form of a bulk-forming laxative is just a drugstore away. While laxatives may bring relief, they should only be used in the short term, unless instructed otherwise by your doctor.

To help prevent constipation in the first place, eat a high-fiber diet consisting of whole grains, fruits, and leafy vegetables. Drink plenty of fluids and avoid constipating foods such as cheese or high-sugar, processed foods.

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