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Chapter 012. Pain: Pathophysiology and Management (Part 8)

Antidepressant Medications The tricyclic antidepressants [amitriptyline, imipramine, nortriptyline, desipramine (TCAs; Table 12-1)] are extremely useful for the management of patients with chronic pain. Although developed for the treatment of depression, the tricyclics have a spectrum of dose-related biologic activities that include the production of analgesia in a variety of clinical conditions. Although the mechanism is unknown, the analgesic effect of TCAs has a more rapid onset and occurs at a lower dose than is typically required for the treatment of depression. Furthermore, patients with chronic pain who are not depressed obtain pain relief with antidepressants. . | Chapter 012. Pain Pathophysiology and Management Part 8 Antidepressant Medications The tricyclic antidepressants amitriptyline imipramine nortriptyline desipramine TCAs Table 12-1 are extremely useful for the management of patients with chronic pain. Although developed for the treatment of depression the tricyclics have a spectrum of dose-related biologic activities that include the production of analgesia in a variety of clinical conditions. Although the mechanism is unknown the analgesic effect of TCAs has a more rapid onset and occurs at a lower dose than is typically required for the treatment of depression. Furthermore patients with chronic pain who are not depressed obtain pain relief with antidepressants. There is evidence that tricyclic drugs potentiate opioid analgesia so they may be useful adjuncts for the treatment of severe persistent pain such as occurs with malignant tumors. Table 12-2 lists some of the painful conditions that respond to tricyclics. TCAs are of particular value in the management of neuropathic pain such as occurs in diabetic neuropathy and postherpetic neuralgia for which there are few other therapeutic options. Table 12-2 Painful Conditions that Respond to Tricyclic Antidepressants Postherpetic neuralgia Diabetic neuropathy Tension headache Migraine headache Rheumatoid arthritis 0 Chronic low back pain0 Cancer Central post-stroke pain Controlled trials demonstrate analgesia. Controlled studies indicate benefit but not analgesia. The TCAs that have been shown to relieve pain have significant side effects Table 12-1 Chap. 386 . Some of these side effects such as orthostatic hypotension drowsiness cardiac conduction delay memory impairment constipation and urinary retention are particularly problematic in elderly patients and several are additive to the side effects of opioid analgesics. The serotonin-selective reuptake inhibitors such as fluoxetine Prozac have fewer and less serious side effects than TCAs but they are much less .