Role of the tricyclic antidepressants in the treatment of chronic pain
Multiple tricyclic antidepressants including amitriptyline, imipramine, doxepin, desipramine, and nortriptyline have consistently shown analgesic effects at doses typically lower than required to treat depression. Amitriptyline, doxepin, and imipramine tend to have a greater side effect burden than desimpramine and nortriptyline. However, it is extremely important to recognize that despite the reduced side effects associated with those agents, the analgesic benefit was not compromised. This should be considered when prescribing these agents. These agents have been used for the treatment of neuropathic pain, chronic headache, chronic low back pain, fibromyalgia, and various other chronic pain states. Side effects of these agents include anticholinergic side effects such as dry mouth, urinary retention, and constipation, as well as sinus tachycardia, blurred vision, confusion, hallucinations, cognitive dysfunction, orthostatic hypotension, and weight gain. Dangerous drug-drug interactions may occur with monoamine oxidase inhibitors, as with other medications whose use could result in increasing central serotonin (serotonin specific reuptake inhibitor [SSRI] agents, for example). The prescriber should consult the pharmacist and other sources for any questions regarding drug-drug interactions. Although widely used, no tricyclic antidepressants (TCA) are FDA approved for the treatment of chronic pain.