The Food and Drug Administration has approved the antidepressant duloxetine for the management of chronic musculoskeletal pain in adults, the agency announced Nov. 4
The approval marks the fifth of duloxetine’s U.S. licensed indications to date and its third for treatment of pain. Duloxetine, marketed as Cymbalta, was first approved in 2004 to treat depression, and later the drug gained indications for generalized anxiety disorder, diabetic neuropathy, and fibromyalgia. All of the indications are for people aged 18 years and older. The drug has received European Union marketing authorization for depression, anxiety, and diabetic neuropathy only.
The mechanism by which duloxetine, a serotonin and norepinephrine reuptake inhibitor, works on pain is uncertain, Eli Lilly said in a press statement accompanying the announcement. However, it is believed to increase the availability of both neurotransmitters, enhancing the body’ natural pain-suppressing system.
In August the FDA’s Anesthetic and Life Support Drugs Advisory Committee had voted 8 to 6 to recommend the extension of indication for duloxetine, a vote that was considered too narrow to predict what the agency would ultimately decide. The drug’s effectiveness was not well agreed upon, either, with an 8 to 5 vote in favor, and one member abstaining.
Evidence from two studies submitted to the agency by the manufacturer (n = 236 and n = 401) showed that duloxetine at oral doses of 60-120 mg daily reduced chronic lower back pain better than placebo after 12 and 13 weeks. Evidence from a third study (n = 404) showed no benefit. For osteoarthritis, one study (n = 256) showed a statistically significant reduction in pain after 13 weeks in people taking between 60 and 120 mg, and another study (n = 231) did not.
The maximum dosage for the musculoskeletal pain indication, which includes osteoarthritis and lower back pain, is 60 mg/day, the same as the maximum recommended dosage for depression.
Adverse events observed in the musculoskeletal pain studies included nausea, dry mouth, insomnia, sleepiness, constipation, dizziness, fatigue, and constipation.
Osteoarthritis affects 27 million American adults, the company said. An estimated 70%-85% experience low back pain at some time, with some reports estimating that up to a tenth of these will go on to have chronic back pain.