Psychiatry - December 2008 - (Page 17)

[the interface] 2007 study, Barrett et al5 found that the average annual cost of pain medication per diabetic patient with peripheral neuropathy was just over $1,000. HOW ANTIDEPRESSANTS WORK IN PAIN MANAGEMENT The explicit way in which antidepressants are effective in pain management remains unknown, but multiple mechanisms are likely to be involved.6 Perhaps the most popular theory is that antidepressants exert their effects on serotonin and norepinephrine, particularly along the descending spinal pain pathways. Antidepressants may also exert adjunctive therapeutic influences through histamine receptors as well as modulation of sodium channels.6 NEUROPATHIC PAIN AND DEPRESSION One common comorbid psychiatric diagnosis encountered in patients with neuropathic pain is depression, which affects the majority of individuals (i.e., 57%).1 Studies indicate that patients with pain have a substantially increased risk for depression, anywhere from 2 to 5 times that of the general population.7 Given that these syndromes are commonly comorbid, the assessment of depression in the presence of pain is typically complicated by the presence of shared features between the two syndromes (e.g., fatigue, sleep disturbance). In addition, the format for assessment may affect findings. Specifically, prevalence rates of depression among pain patients are seemingly higher when assessed through self-report measures compared with standardized diagnostic approaches.2 Investigators have also found that the prevalence rate of depression among pain patients may vary as a function of the clinical setting. In a review of the literature, Bair et al8 found that the prevalence of depression among pain patients in psychiatry clinics was 35 percent, in pain clinics 38 percent, in rheumatology clinics 52 percent, and in dental clinics 78 percent. Surprisingly, despite the frequent comorbidity of pain and depression, Jackson and St. Onge indicate that both remain under-recognized and under-treated in this clinical population.1 While various relationships between pain and depression might be postulated, the most common hypotheses for their comorbidity are that (a) depression precedes pain; (b) pain precedes depression; (c) prior depression heightens the risk of subsequent depression in the presence of new-onset pain; and (d) the two phenomena occur independently of each other. Regardless of the relationships between the two syndromes, Tricyclic antidepressants. TCAs are the most studied antidepressants for the treatment of neuropathic pain and are a mainstay in the treatment armamentarium.1 These antidepressants inhibit the reuptake of serotonin and norepinephrine at the synapse, but do so differentially according to chemical structure. The tertiary amines (e.g., amitriptyline, doxepin, imipramine) inhibit serotonin to a greater degree than norepinephrine. In contrast, the secondary amines (e.g., desipramine, nortriptyline) have more pronounced effects on norepinephrine. While some authors report approximately equal efficacy between these two subclasses of TCAs,4 others advise that the tertiary amines are somewhat more effective than the secondary amines.1,2,6 Interestingly, pain relief appears to be independent of the antidepressant effects of these drugs and may be achieved at doses lower than those used in the treatment of Studies indicate that patients with pain have a substantially increased risk for depression, anywhere from 2 to 5 times that of the general population.7 according to Sullivan and Robinson, the level of comorbidity between pain and depression is one of the basic rationales for considering antidepressant therapy as a treatment.9 However, this is not an exclusive relationship as the doses of TCAs used to treat pain are often much lower than those used to treat depression and depression is not always present in those who experience pain relief. depression. While TCAs are reliable and effective, their use is potentially complicated by a host of beleaguering side effects (e.g., weight gain, anticholinergic effects, orthostatic hypotension, cardiovascular effects, lethality in overdose). Selective serotonin reuptake inhibitors. Selective serotonin reuptake inhibitors (SSRIs) exert their efficacy predominantly through the reuptake inhibition of serotonin. Compared with TCAs in the management of neuropathic pain, the data with regard to SSRIs is more inconsistent3,6 and studies are considerably fewer in number. To date, paroxetine and citalopram have 12, DECEMBER ANTIDEPRESSANTS AND NEUROPATHIC PAIN Many antidepressants are effective in the treatment of pain, but not all and not to the same degree. [VOLUME 5, NUMBER Psychiatry 2008 17

Table of Contents Feed for the Digital Edition of Psychiatry - December 2008

Psychiatry - December 2008 Editor’s Message Contents Editorial Advisory Board Antidepressant Prescribing by Specialty and Treatment of Premenstrual Dysmorphic Disorder Pain, Pain, Go Away: Antidepressants and Pain Management Why Psychotherapy Helps the Patient in Chronic Pain General Medical Drugs Associated with Depression Katatonia: A New Conceptual Understanding of Catatonia and a New Rating Scale Thermoregulation and the Role of Calcium Signalling in Neurotransmission Cognition and Schizophrenia: Is There a Role for Cognitive Assessments in Diagnosis and Treatment? Journal Watch Information for Authors

Psychiatry - December 2008

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