Objectives: Tricyclic antidepressants (TCA) have been shown to provide analgesia for a variety of neuropathic and headache pain syndromes regardless of the presence of depression. There is a high incidence of depression in patients with chronic pain, thereby making tricyclic antidepressants particularly suitable for chronic pain patients. We wanted to study patterns of use of tricyclic antidepressants in our Pain Management Center (Beth Israel Hospital, Boston, MA, U.S.A.) primarily to answer four questions: (1) What percentage of all patients were treated with tricyclic antidepressants? (2) How many patients were treated with each antidepressant, and what was the dose range used for individual antidepressants? (3) Were tricyclic antidepressants beneficial for chronic pain, and was that response dependent on a particular dose? (4) Did patients receive an adequate TCA trial, and what factors led to the discontinuation of a TCA trial?
Methods: A total of 1,145 pain clinic patient charts were reviewed in alphabetical sequence. A total of 282 patients were identified as being treated with tricyclic antidepressants. Data were obtained from these 282 charts regarding the patient's age, diagnosis, tricyclic antidepressant use and dose, other pain treatments, response to treatment, and side effects. The existing diagnosis of depression was documented if possible. Tricyclic antidepressant doses were defined as low doses when the equivalent of 50 mg or less of amitriptyline was used, and as full doses when the equivalent of at least 150 mg of amitriptyline was used. Response to treatment was noted as mild, moderate, or marked improvement. Patients reporting mild improvement were considered nonresponders.
Results: Of 1,145 patients, 282 were treated with tricyclic antidepressants. A total of 205 (73%) of the patients were treated with low doses and only 34 (12%) with full doses. The remaining 43 (15%) received intermediate doses. Amitriptyline was the most commonly used drug (58%). Amitriptyline and doxepin appeared to be more effective than other tricyclic antidepressants. The rate of response to our treatment among the 31 patients with a coexisting diagnosis of depression was similar to the patients without documented depression. In patients with tricyclic antidepressants as the only treatment, there was only a trend toward greater response with full dose. In terms of side effects causing dose limitation or discontinuation of the drug, clomipramine, amitriptyline, and doxepin appeared to be worse than imipramine, desipramine, and nortriptyline.
Conclusion: Tricyclic antidepressants were used in 25% of patients referred to a multidisciplinary pain center and were commonly used in low to intermediate doses, even in situations in which there were neither side effects nor optimal clinical response.