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October 2008

Two Drugs for Fibromyalgia
Pregabalin (Lyrica) and duloxetine (Cymbalta) are approved in the United States for the treatment of fibromyalgia.

Preventing Poststroke Depression
In a 2008 study by Robinson and colleagues, escitalopram (Lexapro) and problem-solving therapy decreased the likelihood of poststroke depression.

Duloxetine for Elderly Patients with GAD
Due to possible adverse events, duloxetine (Cymbalta) should be a second-line option for elderly patients with generalized anxiety disorder.

In Brief
Switch to Aripiprazole Reduces Cardiovascular Risk in Schizophrenia; SSRIs Are Effective for Treating PMS/PMDD; Statins May Protect Against Dementia

Antidepressants for Social Anxiety Disorder
Sertraline (Zoloft and others), paroxetine (Paxil and others), venlafaxine (Effexor and others), and fluvoxamine (Luvox and others) appear to be the most efficacious antidepressants for the treatment of social anxiety disorder, with escitalopram (Lexapro) a reasonable alternative.

Two Drugs for Fibromyalgia

October 2008

Fibromyalgia is characterized by diffuse musculoskeletal pain occurring in a defined pattern and reproduced by pressure on "trigger points." It is estimated to occur in 2% to 10% of the population, affecting women more than men. Associated symptoms include fatigue, nonrestorative sleep, and irritable bowel symptoms. Concurrent depression is common.

Nonpharmacologic treatment for fibromyalgia has included exercise and cognitive behavioral therapy. Hypnotics are sometimes prescribed to address insomnia and analgesics for pain. Although the tricyclic antidepressant amitriptyline (Elavil and others) has been widely used in fibromyalgia, the US Food and Drug Administration (FDA) has approved only pregabalin (Lyrica) and duloxetine (Cymbalta) for this condition. The Medical Letter reviewed the safety and efficacy of these two drugs.

Pregabalin is structurally similar to gabapentin (Neurontin and others). In addition to fibromyalgia, it is approved to treat neuropathic pain associated with postherpetic neuralgia, diabetic peripheral neuropathy, and for the adjunctive treatment of partial-onset seizures in adults with epilepsy.1 Pregabalin is a schedule V controlled substance. Common adverse effects include dizziness, somnolence, fatigue, constipation, euphoria, and peripheral edema. Less common but potentially serious are ataxia, incoordination, angioedema, and confusion. The pregabalin dose recommended for fibromyalgia is 75 mg bid to start, titrated to 150 to 225 mg bid. Some experts begin with 50 mg at bedtime and increase after 1 to 2 weeks to 75 mg at bedtime, titrating slowly to the manufacturer's recommended doses.

The serotonin-norepinephrine reuptake inhibitor (SNRI) duloxetine, already marketed for the treatment of depression, generalized anxiety disorder, and diabetic neuropathy pain, is the second drug to receive FDA's approved labeling for fibromyalgia.2 Clinical studies have found 60 to 120 mg of duloxetine daily more effective than placebo in reducing pain in fibromyalgia patients. Patients with comorbid depression appear to experience even greater relief of pain than patients without depression.

Adverse effects with duloxetine are similar to those of other SNRI antidepressants and include nausea, decreased appetite, dry mouth, insomnia, headache, increased blood pressure, and sexual dysfunction. Long-term use may cause weight gain. Rare cases of hepatitis and hepatic failure, potentially fatal, have occurred with duloxetine.

Metabolized by the cytochrome P450 isoforms 1A2 and 2D6, duloxetine serum concentrations can be increased by drugs that inhibit 1A2 or 2D6, which can lead to duloxetine toxicity. Duloxetine itself is a moderate inhibitor of 2D6.

The recommended dose for treating fibromyalgia with duloxetine is 30 mg once daily for 1 week, then 60 mg once daily. Nausea is diminished when duloxetine is taken with food. Duloxetine is not recommended in patients with severe hepatic or renal impairment.

The Medical Letter estimates that a month's supply of duloxetine will cost $133.50, while a similar supply of pregabalin should cost $139.80. The two drugs operate by different mechanisms and have different adverse effect profiles. Conceivably, they could be used together, although this combination has not been studied and should be employed, if at all, with great caution.

1Pregabalin (Lyrica) for fibromyalgia. Med Lett Drugs Ther 2007;49:77-78.

2Duloxetine (Cymbalta) for fibromyalgia. Med Lett Drugs Ther 2008;50:57-58.