Tricyclic-antidepressant-induced delirium and plasma drug concentration.

Fourteen patients receiving routine doses of amitriptyline developed plasma drug concentrations above 300 ng/ml. Of the 7 patients with plasma levels above 450 ng/ml, 6 developed a drug-induced delirium as opposed to none of the 7 with levels below 450 ng/ml. Thus, this adverse effect could be avoided by monitoring levels and reducing dosage when appropriate.