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Clinician’s Corner: Fiber supplements

The most common first line therapies recommended for patients with frequent constipation is fiber supplementation.  The best option is a change of diet to include more fresh fruits and vegetables.  When that doesn’t provide adequate relief from constipation fiber supplements can be used.  The chemical composition of fiber supplements is what makes each one of these unique. Fiber supplements work as laxatives that cause soften of feces in 1-3 days

Generic Representative Brand Dosage
Methylcellulose Citrucel® 4-6 gm per day
Wheat Dextrin Benefiber® 2 teaspoon up to 3 times daily
Psyllium Metamucil®,  Konsyl® Varies
Polycarbophil FiberLax®, Fibercon® 4-6gm per day

Bulk Forming Agents:

Fiber’s job is to  absorb water to soften stool and increase bulk, which stimulates bowel contractions. The recommended levels for dietary fiber is 25 g/d  (about 1 ounce) for adult women, 38 g/d for adult men (consisting of fruits, vegetables, legumes, whole grains)  About 90% of the US population does not consume this level of dietary fiber, averaging only 15 g/d (1/2 ounce).  Because dietary fiber works in both small and large intestines the onset of action is slow (12-24 hours—up to 72 hours.).   Fiber supplements are used to prevent rather than treat constipation.  Insoluble fiber does not absorb water; while soluble fiber does. Both help material move through your digestive tract, but soluble fiber can help give stool a softer, bulkier consistency that’s easier to pass.

Metamucil®: is made from ground psyllium husks, from the plantago ovata plant.

Adult dose is 1-2 rounded teaspoonful in 8oz of water 1 to 3 times daily.  If using the “Orange Smooth-Real Sugar” product the dose is 1 tablespoonful.

Fun Fact: Metamucil website has dosages for

o   For helping feel less hungry between meals

o   For promoting and maintaining digestive health

o   For helping lower cholesterol to promote heart health- (psyllium traps bile acids)

o   For helping maintain healthy blood sugar levels as part of your diet

Points to remember:

  • There are Metamucil capsules available, if patients complain of grittiness especially if they wear dentures
  • Make sure patients mix with adequate water
  • Because of fermentation it may cause abdominal cramping, bloating, flatulence, distention, esophageal obstruction, intestinal obstruction, allergic reactions
  • Drug interactions: oral anticoagulants, digitalis, salicylates, tetracyclines


synthetic bulk laxative containing methylcellulose.  Methylcellulose is derived from cellulose which comes from the cell walls of green plants. It is less likely to cause fermentation leading to bloating and flatulence.

Dose: 1 tablespoonful 1 to 3 times daily.

Points to remember

o   Available as orange flavor, sugar free and caplets.

o   Be sure to mix with adequate fluids to prevent esophageal obstruction.

o   Mix with cold fluids, avoiding carbonated beverages and milk.


ingredient: wheat dextrin, which is extracted from wheat starch.  Wheat dextrin is a soluble fiber which absorbs water in the intestine to form a viscous liquid which promotes peristalsis and reduces transit time. Helps lower cholesterol, reduces risks of  heart disease and type 2 diabetes. May be beneficial lowering blood sugar and reducing risk for heart disease.

Dose 2 teaspoonfuls daily, up to 3 times daily.

Patient counseling points:

  • Will not thicken in liquid, no taste, no gritty texture.
  • Will not alter taste of food or beverages.
  • May mix with water, juice, coffee, baked goods
  • Patients should avoid if they are gluten sensitive

Calcium polycarbophil

(FiberLax®, FiberCon & Equilactin): can be used for both diarrhea and constipation.  Is a “stool normalizer”. Polycarbophil absorbs about ten times its own weight of water under acidic conditions, but the swells to 70 times its weight in the neutral pH of the small and large intestines.

Each caplet contains 625mg calcium polycarbophil=500mg polycarbophil

Dose: 2 caplets 1 to 4 times daily.

Your Thompson pharmacist is a great resource for appropriate laxative selection.  If you are interested in using fiber supplements “Go ahead and ask— at Thompson Pharmacy, it’s all for YOU!”