Figure 5.

Tricyclic antidepressant assays. A) Rank of tricyclic antidepressants, cyclobenzaprine, and quetiapine by total number of prescriptions in the United States in the time period from 1998–2007. TCAs are indicated by closed symbols, while the non-TCAs (cyclobenzaprine and quetiapine) are designated by open circles and squares, respectively. Whereas prescriptions for amitriptyline have remained relatively constant in the last decade, prescriptions for other TCAs are steadily declining, with desipramine no longer ranking in the top 400 most prescribed drugs. Cyclobenzaprine is now prescribed more frequently than amitriptyline in the United States. B) Drugs most likely accounting for positive TCAs immunoassay screens in our medical center sample. Of 124 positive TCA screens (see Additional file 1, tab U for details), the most likely causes were sorted into five categories: cyclobenzaprine, amitripytline +/- nortriptyline, other TCAs (e.g. doxepine, imipramine, and their metabolites), phenothiazines, and other drugs (e.g., carbamazepine and quetiapine).