It is extremely important for FM patients to realize that many medications, including sedatives, muscle relaxants, tranquilizers, antianxiety drugs, antidepressants, and narcotic pain medications, add significantly to an already-overwhelming fatigue. It’s a toss up whether or not the added sleep they provide can produce enough energy to overcome their sapping effects. The list of medications that can cause somnolence is long, and many patients are taking more than one of them. I urge all patients with unrelenting fatigue to review their medications with a pharmacist and check for this common contributing factor. Over-the-counter nonsteroidal anti-inflammatories and analgesics may also contribue to decreased energy production, according to some studies.
(Source: What Your Doctor May NOT Tell You About Fibromyalgia, by R. Paul St. Amand, M.D., and Claudia Craig Marek.)