By Pat Anson, Editor
Two drugs commonly prescribed for fibromyalgia – Lyrica and Cymbalta – are more effective in treating the disorder when used together, according to a new study by Canadian researchers.
Lyrica (pregabalin) is an anti-seizure nerve drug, while Cymbalta (duloxetine) works primarily as an anti-depressant. Both have been used for years to treat fibromyalgia -- a poorly understood disorder characterized by deep tissue pain, fatigue, insomnia, and mood swings. Until now no one has studied how effective the two drugs could be when used in combination.
"We are very excited to present the first evidence demonstrating superiority of a duloxetine-pregabalin combination over either drug alone," said lead author Ian Gilron, MD, Director of Clinical Pain Research at Queen’s University in Kingston, Ontario.
“The results of this trial suggest that combining pregabalin with duloxetine can safely improve outcomes in fibromyalgia including pain relief, physical function and overall quality of life.”
This was a small study – only 41 fibromyalgia patients participated – and the researchers admit that larger trials are needed to see if the results can be replicated. The new research was published in the journal Pain.
The study is the latest in a series of clinical trials -- funded by the Canadian Institutes of Health Research -- which Gilron and his colleagues have conducted on combination therapies for chronic pain conditions. By studying promising drug combinations, they hope to show physicians how to make the best use of current treatments.
"The value of such combination approaches is they typically involve drugs that have been extensively studied and are well known to health-care providers," says Gilron.
Patients in the study were divided into three groups that either took pregabalin alone, duloxetine alone or a combination of the two for six weeks. Doses were gradually increased in the study to the maximum tolerated dose. When used in combination, patients could only tolerate relatively low doses of pregabalin and duloxetine, suggesting the drugs have an overlap effect when used together.
“The pharmacological diversity of a pregabalin-duloxetine combination is a mechanistically appealing feature that increases the likelihood of additive analgesic actions although there could similarly be some additive adverse effects with this combination. Even at significantly lower doses during combination therapy, superior global pain relief during combination therapy would suggest a greater additive effect for pain reduction than for side effects,” said Gilron.
The biggest side effect of the pregabalin-duloxetine combination was drowsiness, and the researchers admit that reduced physical activity caused by drowsiness could have contributed to pain reduction.
Patients have long complained of other side effects from pregabalin and duloxetine when used separately, such as weight gain, nervousness, and brain fogginess. Many have also reported severe withdrawal symptoms and “brain zaps” when trying to get off the drugs. The study apparently didn’t address those issues.
Lyrica (pregabalin) is one of Pfizer’s top selling drugs and generates over $5 billion in revenue annually. In addition to fibromyalgia, Lyrica is approved by the Food and Drug Administration to treat chronic pain associated with epilepsy, shingles, diabetic peripheral neuropathy, and spinal cord injury. The drug is also prescribed “off label” to treat lumbar spinal stenosis, the most common type of lower back pain in older adults.
Cymbalta (duloxetine) generated sales of $5 billion for Eli Lilly until its patent expired in 2013 and cheaper generic versions of duloxetine became available. Cymbalta is approved for fibromyalgia, neuropathy, osteoarthritis, depression and anxiety.
Only one other medication – Savella – is approved by the FDA for fibromyalgia, but it is not as widely used as the other drugs.
Fibromyalgia was initially thought to be a musculoskeletal disorder, but research now suggests it's a disorder of the central nervous system - the brain and spinal cord. Researchers believe that fibromyalgia amplifies painful sensations by affecting the level and activity of brain chemicals responsible for processing pain signals. It affects twice as many women as men.