Cymbalta for Fibromyalgia
Cymbalta (duloxetine HCl) is a prescription drug originally developed as an anti-depressant medication. It was approved by the US Food and Drug Administration (FDA) in 2008 to also treat the pain associated with fibromyalgia, as well as to improve overall functioning in fibromyalgia patients. In addition to major depressive disorder and fibromyalgia pain, Cymbalta is also approved to treat generalized anxiety disorder, diabetic nerve pain, and for the management of chronic musculoskeletal pain resulting from chronic osteoarthritis and chronic low back pain. An estimated 30% of fibromyalgia patients suffer from depression and as many as 20% also suffer from generalized anxiety disorder; therefore, the fact that Cymbalta is approved to treat fibromyalgia pain as well makes this medication a potentially useful therapeutic option for many fibromyalgia patients.
Cymbalta belongs to a class of drugs called selective serotonin and norepinephrine reuptake inhibitors (SNRIs). SNRIs are predominantly antidepressant medications , and work by regulating the amounts of various neurotransmitters in the brain. SNRIs affect levels of the neurotransmitters serotonin and norepinephrine, both of which are thought to play a key role in the way that pain signals are transmitted throughout the body.
Cymbalta is available in capsule form in 20mg, 30mg, and 60mg strengths, and is typically taken once per day to relieve fibromyalgia pain. It can be taken with or without food, however the capsule should never be broken, opened, or chewed. The maximum dose generally used to treat fibromyalgia pain is 60 mg/day. Patients will typically be started at 30mg/day and treated at that dose for one week, then the dose will likely be increased to 60mg/day. Studies have shown that for most patients, there is no advantage to taking 60mg/day versus 30mg/day, and exceeding 60mg/day typically results in an increase in side effects.
In clinical studies where Cymbalta was studied in relation to its effect on fibromyalgia pain and functioning, the most frequently reported side effect was nausea. Other common side effects included daytime sleepiness, fatigue, constipation, dizziness, agitation, decreases in appetite, dry mouth, and increased sweating. Post-market side effects reported for Cymbalta for all approved indications have also included heart palpitations, vertigo, blurred vision, chills, rash, and hot flushes.
Studies of antidepressants in general have shown that both adults and children with major depressive disorder may experience increased symptoms of depression or possible onset of suicidal thoughts and behaviors. Therefore, it is very important to understand that SNRI medications like Cymbalta have the potential for such side effects. In fact, Cymbalta is not approved for use in anyone under the age of 18. Furthermore, patients who take Cymbalta, as well as their friends and family members, should be attentive to new or deteriorating psychological symptoms, changes in behavior, the onset of suicidal thoughts, increased anxiety levels or agitation, panic attacks, sleeping troubles, aggression, or noticeable increases in hyperactivity. These may occur following initiation of therapy with Cymbalta, after increases in dose, or at any other time. If such changes do become evident, patients, or their friends or family, should contact the treating physician without delay.
In addition to the potential worsening of psychological symptoms, Cymbalta has the potential to interact negatively with a variety of other medications. Individuals who have taken (or recently taken) medications known as monoamine oxidase inhibitors (MAOIs) should not take Cymbalta. Examples of MAOIs include Marplan, Nardil, and Parnate. In addition, Cymbalta has the potential to aggravate pre-existing bleeding disorders, and therefore should be used with caution when taken concurrently with non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen, or blood thinning medications such as warfarin (Coumadin).
Cymbalta has also been shown to cause orthostatic hypotension in some patients. Orthostatic hypotension is low blood pressure that occurs when rising from a sitting position to standing. It can result in lightheadedness, dizziness, or even fainting. Treatment with Cymbalta has also been reported to result in serotonin syndrome and neuroleptic malignant syndrome. Serotonin syndrome is characterized by excess levels of the neurotransmitter serotonin in the body, and can lead to potentially life-threatening seizures and fever. Neuroleptic malignant syndrome is also life-threatening, and characterized by high fever, sweating, unstable blood pressure, disorientation, muscle rigidness, and nervous system dysfunction. Finally, treatment with Cymbalta should be discontinued gradually in order to minimize the risk of withdrawal symptoms such as dizziness, nausea, headache, fatigue, vomiting, increased irritability, insomnia, diarrhea, and anxiety.
Cymbalta should not be taken by individuals with pre-existing liver disease or those who have a history of heavy alcohol use, due to the potential for liver damage. Individuals with narrow-angle glaucoma or those with kidney problems should not use Cymbalta. In addition, those with a history of seizure disorders, abnormal blood pressure, and digestive difficulties should use Cymbalta cautiously.
Overview of Cymbalta Research
Several randomized, double-blind, placebo-controlled trials (the “gold standard” of research design for studies that seek to investigate the effectiveness of a particular treatment) provided the initial base of evidence supporting the safety and efficacy of Cymbalta as a treatment for fibromyalgia pain. The first study, conducted by Arnold and colleagues in 2004, randomized 207 fibromyalgia patients (all of whom met the American College of Rheumatology [ACR] diagnostic criteria for fibromyalgia) to receive either 60mg of Cymbalta or a placebo twice a day for 12 weeks. At the conclusion of the study, those treated with Cymbalta showed significant improvements in pain severity, number of tender points, stiffness, and various quality of life measures when compared to control subjects (Arnold et al., 2004). A subsequent study published the following year by the same group of researchers randomized 354 female fibromyalgia patients to receive 60mg of Cymbalta once a day, 60mg Cymbalta twice per day, or a placebo for a period of 12 weeks. Following analysis of the findings, the researchers found that those who were treated with Cymbalta, regardless of dose, experienced significant improvements in pain severity and several quality of life measures when compared with control subjects. Roughly half of the patients in both Cymbalta treatment groups experienced at least a 30% improvement in their pain severity, versus only 23% in the placebo group. The researchers concluded that both doses of Cymbalta (60mg daily, or 120mg daily) were safe and effective at treating the pain associated with fibromyalgia (Arnold et al., 2005). Russell et al. (2008) randomly assigned 520 fibromyalgia patients (all of whom met ACR diagnostic criteria) to receive either 20mg, 60mg, or 120 mg of Cymbalta, or a placebo, daily over the course of six months. After both three and six months of treatment, those receiving 60mg and 120mg of Cymbalta showed significant improvement in pain severity when compared to those who received 20mg or placebo (Russell et al., 2008).
Since gaining FDA approval in 2008, researchers continue to evaluate Cymbalta as a treatment option for fibromyalgia. Recently published articles by prominent fibromyalgia researches have demonstrated its effectiveness in relieving stiffness (Bennett et al., 2012), as well as its use as part of a combined therapeutic regimen involving other medications (Choy et al., 2011).