Do antidepressant medications relieve chronic low back pain?

Journal of Family Practice, Dec, 1993 by Judith A. Turner, Mary C. Denny

Background. Antidepressant medications are commonly prescribed for patients with chronic low back pain. A literature synthesis was performed to determine whether antidepressants are more effective than placebos in decreasing pain, disability, depression, and analgesic medication use in such patients.

Methods. English-language journal articles were identified from MEDLINE and PsycLIT databases, bibliographies, and inquiries to researchers and drug companies. Articles were included if they reported data from placebo-controlled or drug comparison trials of antidepressants for patients with low back pain. Six articles met these criteria.

Results. Three studies compared the effects of antidepressants and placebos on pain; two found no difference and one found a trend toward superiority of imipramine for patients-rated symptoms but no difference in investigator ratings. Effects on functional disability were examined in three antidepressant-placebo comparisons; only one found the antidepressant to be more effective. Antidepressant effects of an antidepressant vs placebo were compared in three studies; none found a significant difference. Effects on analgesic medication use were compared in three studies; one found amitriptyline to be superior and the others found no difference. Serious methodologic flaws characterized all six studies, and insufficient reporting of data procluded meta-analysis.

Conclusions. The literature has not demonstrated that antidepressants are superior to placebos in improving antidepressants are superior to placebos in improving low back pain or related problems. However, further randomized controlled trials are needed to determine whether antidepressants are useful for low back pain.

Back pain is the second leading symptom prompting visits to physicians in the United States.[1] For women 35 to 64 years of age and men 25 to 64 years of age, back discomfort is the leading symptomatic reason for visiting office-based physicians.[2] Data from the National Ambulatory Medical Care Surveys (NAMCS) of 1977 and 1978 revealed that 61% of patients with back symptoms were treated by primary care physicians, and back symptoms ranked second among presenting complaints in the caseloads of internists and general and family practitioners.[1] Data from the 1985 NAMCS also indicate that the physicians who see the most patients with back pain are those in primary care specialties.[3] Similarly, population-based data from the second US National Health and Nutrition Examination Survey (NHANES-II), conducted between 1976 and 1980, indicated that by far the most common provider of care for low back pain was the general practioner (59% of people with low back pain had sought care from a general practitioner).[4]

Patients with back pain are frequently treated with a variety of medications. Drug were prescribed in 61.5% of physician office visits for back symptoms from 1977 to 1978.[1] Although data from that survey have not been published concerning the prevalence of prescription of antidepressant medications for patients with low back pain in primary care, it is known that tricyclic antidepressants were prescribed by primary care physicians in 2% of all office visits made by patients with low back pain in 1985.[3] Even though antidepressant medications have not been approved by the US Food and Drug Administration for the treatment of pain,[3] physicians prescribe antidepressant medications to patients with low back pain for a number of reasons. These include the belief that the antidepressant medication may have analgesic effects, belief that the patient may be depressed (a common concomitant of chronic pain), and belief that help with sleep is needed.[5-7] It is commonly thought that antidepressants relive pain in doses smaller than are needed to relieve depression,[8-12] and that analgesic effects appear earlier than antidepressant effects.[9,13]

Multiple recent articles have suggested that antidepressant medications are helpful for many chronic pain syndromes.[3,5,9,10,14-20] Some authors believe that antidepressant medication helps chronic pain indirectly because of it beneficial impact on depression[21] or sleep or both[20]; others believe it has an analgesic effect independent of its antidepressant action.[22] This analgesic effect has been postulated to relate to similarities between neurotransmitter systems involved in depression and in pain. It has been further hypothesized that serotonergic antidepressants (eg, clomipramine, fluoxetine) have greater analgesic properties than do more nonadrenergic antideperssants becausee serotonergic systems have been shown to be involved in pain in animals.[23,24] In fact, the second-generation antidepressant trazodone was developed in a process that involved testing potential drugs by assessing animal responses to noxious stimuli.[25] However, serotonergic antidepressants have not been found to have greater analgesic effects than nonadrenergi antidepressants,[18] and noradrenergic systems may also be involved in pain.[26,27] Thus, the mechanisms by which antidepressants may relieve depression and pain are more understood.[14,15]