A study recently published in the journal Arthritis Research & Therapy revealed new data from a phase III clinical trial showing that duloxetine is a safe and effective therapy for fibromyalgia patients. The study is entitled “A randomized, double-blind, placebo-controlled phase III trial of duloxetine in Japanese fibromyalgia patients”, and was led by researchers at the Nihon University School of Medicine and the Tokyo Medical University in Japan.

Fibromyalgia is a medical disorder characterized by a set of symptoms that include widespread chronic musculoskeletal pain, incapacitating fatigue, stiffness and numbness in certain parts of the body, painful response to pressure, headaches, unrefreshing sleep (poor sleep quality), anxiety or depression and mood alterations. Fibromyalgia can affect people’s ability to conduct simple daily tasks, compromising their quality of life. It is estimated that 5 to 15 million Americans are affected by this disorder, especially women, and in Japan around 1.7% of the population (approximately 2 million individuals).

Duloxetine, a selective inhibitor of specific neurotransmitters, has been approved for fibromyalgia treatment in the United States. In Japan, however, duloxetine has only been approved for the treatment of major depressive disorder and diabetic peripheral neuropathic pain.

In the study, researchers evaluated the safety and efficacy of duloxetine treatment in a cohort of 393 Japanese fibromyalgia patients in a randomized, double-blind, placebo-controlled phase III clinical trial (NCT01552057). All patients had a confirmed fibromyalgia diagnosis and a Brief Pain Inventory (BPI) average pain score equal or higher than 4. Patients received either duloxetine 60 mg or a placebo once daily for a period of 14 weeks. The main endpoints of the trial were a change in BPI average pain score from baseline, the patient’s quality of life and safety.

Based on a specific covariance analysis called last observation carried forward (LOCF), researchers found a significant improvement in BPI average pain score change and quality of life 14 weeks after therapy in patients under duloxetine treatment in comparison to the placebo group. In terms of safety, duloxetine was generally well tolerated. The most common adverse events reported in patients under duloxetine therapy were somnolence, constipation and nausea.

The research team concluded that duloxetine is a safe and well tolerated therapy that seems to relief pain and improve fibromyalgia patient’s quality of life and related symptoms.