Duloxetine: an effective treatment for fibromyalgia syndrome?

Abstract

Duloxetine hydrochloride (duloxetine) is a powerful selective serotonin and norepinephrine reuptake inhibitor (SSRI), which in recent years has shown measurable success in treating a wide variety of disorders, including fibromyalgia syndrome (FMS). Among the clinical symptoms of FMS is the dysfunction of the monoamine systems in the nervous system, and since those are what duloxetine regulates, it is successful in managing its symptoms.1 Therefore, the United States Food and Drug Administration has cleared it for treating major depressive disorder, generalized anxiety disorder, for managing diabetic peripheral neuropathic pain and chronic musculoskeletal pain2. FMS is prevalent worldwide and affects nearly 1 in 20 people globally, including about 3 million adults in the United States3. Usually, patients diagnosed with FMS also have other chronic overlapping pain conditions and mental disorders, therefore it is uncommon to have FMS as an independent diagnosis4. Chronic stress exacerbates neuropathic pain by integrating stress affect–related information with nociceptive information in the amygdala’s central nucleus5,6. Its symptoms include restless sleep, fatigue, anxiety, depression, and problems regulating mood. There is a central magnification of pain signals, which evidence suggests is caused by the fact that both the ascending and descending pain pathways are functioning abnormally7. Although there is little evidence supporting this, it is believed that the symptoms are caused by neural over-sensitization, decreased conditioned pain modulation, combined with cognitive dysfunction, memory impairment, and altered information processing caused by negative events, stressful environments, or physical/emotional trauma8,9. Patients suffering from FMS have also been reported to experience a phenomenon known as fibrofog, which entails a decreased ability to think and process new information. The inference that disruptions in the perception of physiological pain, sleep, fatigue, cognition, and mood (hallmark symptoms of patients with FMS) may be consequences of abnormalities in serotonin and norepinephrine metabolism and transmission is supported by the fact they are both important regulators of these functions in healthy individuals10. Duloxetine works by reinforcing the serotonergic and adrenergic pathways involved in descending inhibition of pain at the dorsal horn of the spinal cord. The subsequent increased threshold for pain stimuli to reach the brain results in significant neuropathic pain relief. In a study, Write et al11 concluded that because the average FMS patient is on 3–6 medications to manage the symptoms, there may be an increased risk for the drug-to-drug interactions. Serotonin toxicities can develop from using serotonergic drugs and duloxetine simultaneously as it can lead to adverse drug-drug interactions12. Furthermore, little is known about how it may affect pregnancies or lead to complications for the mother and child before and after delivery. SSRIs increase the possibility of developing suicidality in children and young adults aged 18–24, which is one of its more tendentious side effects. Thus, the FDA has released a black box warning for duloxetine use13. Furthermore, duloxetine increases both levels of serotonin and norepinephrine, which directly results in tachycardia and hypertension14. Even though systematic reviews have proven its effectiveness in pain management, improving symptoms in up to 80% of patients, a careful examination of its adverse effects and advantages must be taken into consideration when prescribing SSRIs to any patient13,14. Diagnosis and eventual management of this disease are delayed because patients usually present with a variety of symptoms15. FMS patients must spend up to $35,920 on health care every year in the United States to treat the various symptoms of this disease16. Frequent physical therapy appointments to reduce stiffness, frequent blood work, and hospital visits take up significant time and place a financial strain on the patient. In a recent study, it was found that most patients with FMS view themselves as being moderate to severely disabled. The intensity of pain they experience and psychological factors (alexithymia and depression) were found to be the main reasons for this17. Clear, distinct guidelines for its diagnosis should be established so as not to delay the beginning of treatment, and awareness needs to be created among clinicians in third-world countries about this disease as well. Newer, more effective drugs need to be designed to not only improve the patient’s quality of life but to reduce the burden on the already overwhelmed health care systems as well. Ethical approval None. Sources of funding None. Authors’ contribution N.E.: wrote the article, suggested a topic, conducted a literature search A.E.: conducted a final review and corrections Conflicts of interest disclosure The authors declare that they have no financial conflict of interest with regard to the content of this report. Research registration unique identifying number (UIN) None. Guarantor Naz Elahi.