psyllium
Brand: Metamucil, Konsyl
Prototype Drug
Drug Class: bulk-forming laxative / fiber supplement
Drug Family: GI agent
Subclass: soluble dietary fiber
Organ Systems: gastrointestinalcardiovascular
Mechanism of Action
Absorbs water in the GI tract to form a viscous gel that increases fecal bulk, stimulates peristalsis, and softens stool. Also binds bile acids in the intestinal lumen, reducing their reabsorption and lowering LDL cholesterol through a mechanism similar to bile acid sequestrants.
GI tract (physical bulk mechanism)bile acid resins (cholesterol lowering)
Indications
- constipation
- irritable bowel syndrome (diarrhea-predominant)
- hypercholesterolemia (adjunct)
- prevention of hemorrhoid recurrence
Contraindications
- intestinal obstruction
- difficulty swallowing (must be taken with adequate fluid)
- phenylketonuria (some products contain aspartame)
Adverse Effects
Common
- bloating
- flatulence
- abdominal cramping (initial use)
Serious
- esophageal or GI obstruction if taken without sufficient water
- anaphylaxis (rare, psyllium allergy)
Pharmacokinetics (ADME)
| Absorption | not absorbed; acts entirely within GI lumen |
| Distribution | none (not systemically absorbed) |
| Metabolism | fermented by colonic bacteria |
| Excretion | fecal |
| Half-life | not applicable |
| Onset | 12–72 hours |
| Peak | 1–3 days |
| Duration | varies |
| Protein Binding | none |
| Vd | none |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| warfarin, digoxin, lithium | reduced absorption of orally administered drugs if taken simultaneously | moderate |
| diabetes medications | reduced postprandial glucose absorption may require adjustment | minor |
Nursing Considerations
- Always administer with at least 8 oz (240 mL) of water to prevent esophageal and GI obstruction.
- Separate administration from other oral medications by at least 2 hours to avoid impaired drug absorption.
- Start with lower doses and titrate gradually to minimize GI bloating and gas during the first 1–2 weeks.
- Educate patients with diabetes that psyllium reduces postprandial glucose spikes, which may require monitoring of blood glucose.
Clinical Pearls
- Psyllium is the only FDA-approved fiber supplement with an approved cardiovascular disease risk-reduction claim, as studies demonstrate up to 10–15% reduction in LDL cholesterol.
- Unlike stimulant laxatives, psyllium is safe for chronic long-term use and is appropriate for elderly patients with chronic constipation.
Safety Profile
Pregnancy safe
Lactation generally-safe
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.