Metamucil - Drug Monograph

Introduction

Metamucil is a well-known bulk-forming laxative containing psyllium husk as its active ingredient. It is classified as a dietary fiber supplement and over-the-counter medication primarily used for constipation relief and cholesterol management. Derived from the Plantago ovata plant, psyllium has been used medicinally for centuries and remains one of the most clinically studied fiber supplements available today.

Mechanism of Action

Psyllium husk, the active component in Metamucil, is a hydrophilic colloid that absorbs water in the intestine to form a gelatinous mass. This mechanism provides several therapeutic effects:

• Increases stool water content and bulk
• Softens stool consistency
• Promotes peristalsis through mechanical stimulation of the intestinal mucosa
• Binds to bile acids in the intestine, facilitating their excretion and thereby reducing serum cholesterol levels

The laxative effect typically occurs within 12-72 hours after administration, depending on individual gastrointestinal transit time.

Indications

• Treatment of occasional constipation
• Management of chronic constipation
• Irritable bowel syndrome (symptom management)
• Hemorrhoid management (by softening stools)
• Dietary fiber supplementation
• Adjunct to diet for reducing cholesterol levels (FDA-approved for this indication)
• May help with blood glucose control in diabetes management

Dosage and Administration

• Powder: 1 teaspoon (3.4g) to 2 teaspoons (6.8g) mixed with at least 8 ounces of fluid 1-3 times daily
• Capsules: 2-5 capsules with at least 8 ounces of fluid 1-3 times daily
• Wafers: 2 wafers with at least 8 ounces of fluid 1-3 times daily

• Always take with adequate fluid (at least 8 ounces per dose)
• Mix powder thoroughly in water or juice and consume immediately
• Dose may be titrated based on individual response and tolerance
• Maximum daily dose: 30g of psyllium

• Geriatric: Standard adult dosing with careful attention to fluid intake
• Pediatric: Consult healthcare provider; typically ½ adult dose for children 6-12 years
• Renal/Hepatic Impairment: No dosage adjustment required
• Pregnancy/Lactation: Generally considered safe but consult healthcare provider

Pharmacokinetics

Contraindications

• Known hypersensitivity to psyllium or any product components
• Fecal impaction
• Gastrointestinal obstruction
• Difficulty swallowing
• Symptoms of appendicitis
• Undiagnosed rectal bleeding

Warnings and Precautions

• Esophageal obstruction: May occur if taken without sufficient fluid
• Allergic reactions: Rare but possible, especially in individuals with occupational exposure to psyllium
• Bowel obstruction: Use with caution in patients with preexisting intestinal narrowing
• Diabetes: Sugar-free formulations available for diabetic patients
• Medication absorption: May interfere with absorption of other medications if taken simultaneously

Drug Interactions

• Oral medications: May decrease absorption of concurrently administered drugs including:

- Lithium - Digoxin - Carbamazepine - Warfarin - Antidepressants

• Recommendation: Administer other medications 1-2 hours before or 2-4 hours after Metamucil
• Other laxatives: May potentiate effects of other laxatives

Adverse Effects

• Abdominal bloating
• Flatulence
• Abdominal cramping
• Nausea

• Allergic reactions (rash, itching, difficulty breathing)
• Esophageal obstruction (if taken with insufficient fluid)
• Anaphylaxis (rare)

• Intestinal obstruction (in susceptible individuals)
• Severe allergic reactions

Monitoring Parameters

• Bowel movement frequency and consistency
• Hydration status
• Abdominal symptoms (pain, distension)
• Serum electrolytes (with chronic use in at-risk populations)
• Lipid profile (when used for cholesterol management)
• Blood glucose levels (in diabetic patients)
• Weight and nutritional status with long-term use

Patient Education

• Take with plenty of water: Always consume with at least 8 ounces of fluid
• Mixing instructions: Mix powder thoroughly and drink immediately to prevent thickening
• Timing: Allow 2-4 hours between Metamucil and other medications
• Gradual initiation: Start with lower doses to minimize gastrointestinal effects
• Hydration: Maintain adequate fluid intake throughout the day
• Consistency: Use regularly for best results rather than intermittently
• Diet: Incorporate other fiber sources and maintain balanced nutrition
• When to seek help: Contact healthcare provider if no bowel movement occurs within 3 days, or if severe abdominal pain, vomiting, or rectal bleeding occurs

References

1. McRorie JW. Evidence-Based Approach to Fiber Supplements and Clinically Meaningful Health Benefits, Part 1. Nutrition Today. 2015;50(2):82-89. 2. Anderson JW, et al. Cholesterol-lowering effects of psyllium intake adjunctive to diet therapy in men and women with hypercholesterolemia: meta-analysis of 8 controlled trials. American Journal of Clinical Nutrition. 2000;71(2):472-479. 3. FDA Drug Monograph: Psyllium Husk. OTC Monograph M002. 4. Slavin JL. Position of the American Dietetic Association: health implications of dietary fiber. Journal of the American Dietetic Association. 2008;108(10):1716-1731. 5. Marlett JA, et al. Comparative laxation of psyllium with and without senna in an ambulatory constipated population. American Journal of Gastroenterology. 1987;82(4):333-337. 6. Product prescribing information: Metamucil (Procter & Gamble).