The depression therapy market is one of the largest in the world. Antidepressant sales now constitute the largest segment, approximately 24%, of the central nervous system pharmaceutical market, according to a report by market research firm Decision Resources. The blockbuster status antidepressants have achieved may reach new highs now that many of them are being prescribed for medical conditions such as fibromyalgia, and clinical trial results are emerging that underscore their merit.

A German study identified 18 randomized controlled trials (median duration, eight weeks) that involved 1427 participants. Researchers from the Klinikum Saarbrücken evaluated the effects of four types of antidepressants: tricyclic and tetracyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), serotonin and noradrenaline reuptake inhibitors (SNRIs), and monoamine oxidase inhibitors (MAOIs). Effects were summarized using standardized mean differences (SMDs) by a random-effects model.

There was strong evidence for an association of antidepressants with reduction in pain (SMD, -0.43; 95% confidence interval [CI], -0.55 to -0.30), fatigue (SMD, -0.13; 95% CI, -0.26 to -0.01), depressed mood (SMD, -0.26; 95% CI, -0.39 to -0.12), and sleep disturbances (SMD, -0.32; 95% CI, - 0.46 to -0.18). Also, strong evidence suggested an association with the use of antidepressants and improved HRQOL (SMD, -0.31; 95% CI, -0.42 to -0.20).

Overall, all five FMS symptoms that were evaluated were significantly affected by the use of antidepressants. However, pain was reduced at varying degrees depending on the antidepressant taken. TCAs had the largest effect on reducing pain following MAOIs, while SSRIs and SNRIs had the smallest effects on reducing pain.

But there is still much to be learned about the effects of these medications, according to the investigators.

“Since evidence for a long-term effect of antidepressants is still lacking, their effects should be reevaluated at regular intervals to determine whether benefits outweigh adverse effects,” the authors wrote. “The identification of patient characteristics associated with positive and negative therapeutic outcomes is needed to better target antidepressant therapy for FMS.”

Few effective pharmacological treatment options are currently available for patients with FMS. But this area of research is growing. Researchers from the department of neurology at the University of Wurzburg in Germany reported on two randomized, placebo-controlled trials that have investigated the short-term safety and efficacy of duloxetine HCI (Cymbalta) to treat patients with FMS symptoms. Duloxetine is a new selective serotonin and norepinephrine reuptake inhibitor that is licensed for the treatment of pain in diabetic neuropathy.

Both trials investigated the short-term safety and efficacy of two doses (60 mg/day and 120 mg/day) of duloxetine in FMS patients over a 12-week period. Both dosages were superior to placebo in pain relief. Patients also showed an improvement in quality of life and depressive symptoms. The higher dose of 120 mg/day further reduced the tender point count and elevated the tender point pain thresholds. Only mild to moderate adverse effects were reported. The investigators concluded that duloxetine 60 mg/day and 120 mg/day proved to be beneficial in the treatment of FMS symptoms.

Although the future looks promising for patients suffering from often extremely debilitating FMS-related symptoms, additional studies are needed to assess the long-term efficacy and safety of antidepressants as a pharmacological treatment option for FMS.