If you are currently being treated with any of the following medications, you
should not use fiber supplements without first talking to your healthcare
Antidepressant Medications, Tricyclics
Dietary fiber has been
shown to lower the blood levels and effectiveness of tricyclic antidepressant
medications such as amitriptyline, doxepin, and imipramine in three patients.
Reduced dietary fiber intake increased the blood levels and improved symptoms in
these patients. Individuals currently taking tricyclic medications should
consult a healthcare provider before increasing fiber intake.
While fiber supplements may help to
regulate blood sugar levels, they may also interfere with the absorption of
anti-diabetic medications, specifically glyburide and metformin. Therefore,
fiber supplements should not be taken at the same time as this medication.
Taking soluble fiber such as psyllium with
carbamazepine, a medication used to treat seizure disorders, may decrease the
absorption and effectiveness of carbamazepine. If taking both soluble fiber and
carbamazepine, blood levels of carbamazepine should be monitored closely by a
Combining psyllium or other
soluble fibers with cholestyramine or colestipol (two types of
cholesterol-lowering medications known as bile acid sequestrants) may be
beneficial in lowering cholesterol levels. Individuals taking these medications
should consult a healthcare practitioner to determine whether psyllium is safe
On the other hand, taking fiber in the form of pectin (from fruit) and oat
bran reportedly reduces the body's ability to absorb cholesterol-lowering
medications known as "statins" (such as lovastatin and atorvastatin), and could
lead to decreased effectiveness of this class of medications.
Fiber supplements may reduce the body's ability to
absorb digoxin, a medication used to regulate heart function. Therefore, fiber
supplements should not be taken at the same time as this medication.
Reports suggest that psyllium or other soluble fibers
may lower lithium levels in the blood, reducing the effectiveness of this
medication. Lithium levels should be monitored very closely by a healthcare
provider, particularly if there is any significant change in fiber intake.
In one study, the fiber supplement guar gum reduced
blood levels of penicillin. Therefore, it would be best not to take penicillin
at the same time as fiber supplements.