High-Fiber Diet and Serum Tricyclic Antidepressant Levels

The role of dietary fiber as a cause of antidepressant malabsorption has received little attention. Three patients are described who had previously been successfully treated with tricyclic antidepressants and subsequently became refractory to treatment after commencing a high-fiber diet. Serum antidepressant levels were decreased while the patients ingested the high-fiber diets and rose when the fiber content of the diet was reduced. Clinical improvement of their depression followed the concomitant rise in serum tricyclic antidepressant levels.