Pharmacotherapeutic Management
The best-supported pharmacologic therapy for fibromyalgia is low doses of tricyclic antidepressants. This is the case for a number reasons:
- The pain that occurs with fibromyalgia is not due to activation of nociceptors (a sensory receptor that responds to pain) and shows only minimal response to non-steroidal anti-inflammatories like ibuprofen or naproxen which act primarily on peripheral (outer) tissues.
- Tricyclic antidepressants such as amitriptyline (brand names - Amitril, Elavil, Emitrip, Endip, Enovil, Etrafon) and cyclobenzaprine (brand names - Benzamin, Cloben, Cyben, Flexeril, Flexiban, Tensodox, Yurelax) have been effective in treating the pain associated with fibromyalgia, especially when tolerance-promoting strategies are used. (Godfrey, R. G., 1996); (Carette, S. et al., 1994)
- This class of compounds has demonstrated efficacy on co-morbid conditions, including tension and migraine headaches, irritable bowel syndrome and noncardiac chest pain.
- Tricyclic antidepressants provide the added benefit of improved sleep patterns in patients with disrupted sleep.
Cyclobenzaprine and amitriptyline are the two tricyclic agents studied most in the treatment of fibromyalgia and no difference has been found in effectiveness between these two drugs (Carette, S. et al., 1994). However, clinical trials performed to date only demonstrate short-term benefit. Neither drug has been shown superior to placebo at six months of study. This could represent a rapidly decreasing response to these drugs, but is more likely due to these studies being under-powered and not designed to administer the optimal or most appropriate dose of the drug.
One of the big issues in the use of tricyclic antidepressants has been determining the optimal dosage for each individual. Because tolerance to these drugs is problematic, it is recommended to intiate treatment at low doses of 10 mg or less several hours before bedtime, with slow (10 mg) increases every week or two until an optimal dose is achieved (up to 40 mg of cyclobenzaprine, or 70 mg to 80 mg of amitriptyline).
Because of a better side effect profile, newer antidepressants are frequently used to treat fibromyalgia. Although there are only anecdotal data to support this, many in the chronic pain field feel that agents with greater adrenergic and/or dopaminergic activity (adrenergic relates to the nerve cells or fibers of the autonomic nervous system that use norepinephrine as their neurotransmitter; domapinergic relates to the nerve cells that use dopamine as their neurotransmitter), such as venlafaxine or nefazadone, may be of more benefit than pure serotinergic (related to the action of serotonin - a vasoconstrictor, liberated by blood platelets and inhibits gastric secretions and stimulates smooth muscle) drugs. Fibromyalgia patients can achieve pain management by using tramadol (Ultram) and there also is anecdotal evidence that high doses of gabapentin (Neurontin) and long-acting opioids may be useful for refractory pain (pain that is resistant to treatment). For individuals who do not tolerate tricyclics drugs, alternative such as trazadone, zolpidem or clonazepam may be useful to help improve sleep. A subset of fibromyalgia patients with features of autonomic dysfunction, including orthostatic hypotension, palpitations and/or vasomotor instability, may benefit from the use of low-dose beta blockers and/or increased fluid and sodium/potassium intake.
Reference list
Carette, S., Bell, M. J., Reynolds, W. J., Haraoui, B., McCain, G. A., Bykerk, V. P., Edworthy, S. M., Baron, M., Koehler, B. E., & Fam, A. G. (1994). Comparison of amitriptyline, cyclobenzaprine, and placebo in the treatment of FM. A randomized, double-blind clinical trial. Arthritis & Rheumatism, 37, 32-40.
Godfrey, R. G. (1996). A guide to the understanding and use of tricyclic antidepressants in the overall management of FM and other chronic pain syndromes. Archives of Internal Medicine, 156, 1047-1052.
