If you are currently being treated with any of the following medications, you should not use psyllium supplements without first talking to your healthcare provider.

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 taking tricyclic medications should consult a healthcare provider before increasing psyllium intake.

Carbemazepine
Taking psyllium with carbamazepine, a medication used to treat seizure disorders, may decrease the absorption and effectiveness of carbamazepine. If taking psyllium and carbamazepine, blood levels of carbamazepine should be monitored closely by a healthcare provider.

Cholesterol-lowering Medications, Bile Acid Sequestrants
Combining psyllium with the cholesterol-lowering medications classified as bile acid sequestrants, such as cholestyramine or colestipol, may be beneficial in lowering cholesterol levels and may reduce side effects of colestipol. Consult with your healthcare practitioner about whether this may be an option for you.

Diabetes Medications
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 these drugs.

Digoxin
Fiber supplements may reduce the body's ability to absorb digoxin, a medication used to regulate heart function. Therefore, it is likely that psyllium and psyllium supplements would similarly interfere with the absorption of digoxin and should not be taken at the same time as this medication.

Lithium
Reports suggest that psyllium may lower lithium levels in the blood, reducing the effectiveness of this medication. If both are used, they should be taken at least one hour apart, preferably two. Lithium levels should be monitored very closely by a healthcare provider, particularly if there is any significant change in fiber intake.