Letters to the Editor
The Use of Atomoxetine Adjunctively in Fibromyalgia Syndrome
Dear Editor:
Fibromyalgia syndrome (FMS) is a chronic disease characterized by widespread musculoskeletal pain (1). It is also accompanied by persistent fatigue, nonrestorative sleep, generalized morning stiffness, and multiple tender points (2). FMS occurs more often in women than in men and has an overall prevalence rate of 1% in the population (3). The pathophysiology of FMS is unknown; however, central monoaminergic transmission may be involved (4). No single medication has been found to effectively treat all symptoms of FMS. Selective serotonin reuptake inhibitors (SSRIs), selective serotonin norepinephrine reuptake inhibitors (SNRIs), tricylic antidepressants, hypnotic agents, anticonvulsants, and analgesics have been used to treat the syndrome. The following cases discuss using atomoxetine adjunctively in FMS. To my knowledge, this is the first description of atomoxetine used in the pharmacologic treatment of FMS.
Case Report 1
Ms A is hispanic and aged 35 years. She was referred by her primary care physician for assistance with the pharmacologic management of her fibromyalgia. She had been diagnosed with fibromyalgia 1 year prior to consultation and took sertraline 150 mg daily and cyclobenzaprine 10 mg 3 times daily, as needed. She had a psychiatric history significant for a major depressive episode that had been in remission for about 2 years. She had no active symptoms associated with depression. Her biggest concerns were ongoing fatigue, coupled with a worsening of pain in her tender points, that interfered with her ability to work a consistent 40 hours weekly (she was able to work about 20 hours weekly). She had no other medical problems: recent laboratory test including a complete blood count, comprehensive metabolic panel, liver function test, thyroid-stimulating hormone, erythrocyte sedimentation rate, urinalysis, and pregnancy test were either within normal limits or negative. She did not want to discontinue taking sertraline because she had not tolerated other antidepressants (including venlafaxine and paroxetine) during her depressive episode. She gave informed consent to a trial of atomoxetine to target her symptoms and began atomoxetine 40 mg daily, which was titrated to 80 mg over 1 week with no significant side effects. Over the next 3 weeks, she began to note a reduction in pain and an increase in her energy level. She gradually began to increase her workweek by 5 hours weekly and has now reached 40 hours weekly for the first time in 3 months. She has also begun an aerobic exercise regimen and has lost 20 pounds. She has sustained her improvement over the past 6 months.
Case Report 2
Ms B is hispanic and aged 37 years. She has a history of dysthymic disorder and was referred to her internist to confirm a diagnosis of fibromyalgia. She had not been able to tolerate bupropion for her dysthymic disorder but had done well on escitalopram 10 mg daily. Her internist started her on amitriptyline 50 mg daily and methocarbamol 1 g 4 times daily as needed for pain. She discontinued the amitriptyline after 2 weeks, complaining of excessive sedation and dry mouth. She had no other medical problems and did not use tobacco, alcohol, or illicit substances. Her laboratory examination was within normal limits on a complete blood count, comprehensive metabolic panel, liver enzymes, thyroid-stimulating hormone, erythrocyte sedimentation rate, lyme titer, and urinalysis; her human chorionic gonadotropin was negative. Her main concerns were ongoing multiple tender points and daily fatigue. She gave informed consent to a trial of atomoxetine to target her symptoms and was started at 40 mg daily, increased at 2 weeks’ time to 80 mg and titrated to 120 mg daily at 1 month’s time. She has maintained her marked improvement at 6 months and is working full-time.
Antidepressants are commonly used to treat fibromyalgia. Because the pain associated with fibromyalgia tends to be more centrally than peripherally mediated, medications that raise central levels of norepinephrine are most effective (5). In the treatment of FMS, use of amitriptyline has been best documented (6). Venlafaxine, an SNRI, has also been used to treat FMS (4,7,8). SSRIs used alone do not seem to be effective (6). In the cases described, the patients were taking an SSRI, and their mood disorders were in remission; however, they were experiencing symptoms associated with their fibromyalgia. Instead of switching classes of medication, atomoxetine was added to their regimen. It was chosen because it is a norepinephrine reuptake inhibitor (approved for the treatment of attention-deficit hyperactivity disorder, 9). Although the addition of atomoxetine to existing SSRIs shows promising outcomes in treating FMS, further, more controlled studies are warranted. Additionally, we recommend that physicians prescribing atomoxetine for off-label use appropriately document informed consent weighing both the risks and the benefits, compared with agents that are already FDA-approved for the particular condition. In the case of fibromyalgia, where there is no particular FDA-approved agent, it is important to compare it with agents that have been most widely used in the treatment of fibromyalgia.
References
1. Briley M, Moret C. Fibromyalgia syndrome: an overview of potential drug targets. IDrugs. 2003:6: 668–73.
2. Patkar AA, Bilal L, Masand PS. Management of fibromyalgia. Curr Psychiatry Rep 2003;5:218–24.
3. Rowbotham MC. Other specific pain syndromes. In: Goldman L, Bennett JC, editors. Cecil textbook of medicine. 21st ed. Philadelphia (PA): WB Saunders; 2000. p 2072–3.
4. Sayar K, Aksu G, Ak I, Tosun M. Venlafaxine treatment of fibromyalgia. Ann Pharmacother 2003;37:1561–5.
5. Clauw DJ, Crofford LJ. Chronic widespread pain and fibromyalgia: what we know, and what we need to know. Best Pract Res Clin Rheumatol 2003;17:685–701.
6. Lautenschlager J. Present state of medication therapy in fibromyalgia syndrome. Scand J Rheumatol Suppl 2000;113:32–6.
7. Dryson E. Venlafaxine and fibromyalgia [letter]. N Z Med J 2000;113:87.
8. Dwight MM, Arnold LM, O’Brien H, Metzger R, Morris-Park E, Keck PE Jr. An open clinical trial of venlafaxine treatment of fibromyalgia. Psychosomatics 1998;39:14–7.
9. Kratochvil CJ, Vaughan BS, Harrington MJ, Burke WJ. Atomoxetine: a selective noradrenaline reuptake inhibitor for the treatment of attention-deficit/hyperactivity disorder. Expert Opin Pharmacother 2003;4:1165–74.
Tim Berigan, DDS, MD
Vail, Arizona
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