Fibromyalgia is a syndrome characterized by chronic generalized
pain associated with different
somatic symptoms, such as sleep disturbances,
fatigue, stiffness, balance problems,
hypersensitivity to physical and psychological environmental stimuli, depression and anxiety. It has been estimated to affect roughly the 2-4% of the general population in most countries studied, and it has been shown to be much more prevalent in women than in men. Although its pathophysiology is not yet fully understood, it is known that both genetic and environmental factors are involved in its development.
Fibromyalgia shares a high degree of co-morbidity with other conditions, including
chronic headache,
temporomandibular disorder,
irritable bowel syndrome, major depression,
anxiety disorders and
chronic fatigue syndrome. Therefore, this is a syndrome difficult to treat for which
multimodal treatments including physical exercise, psychological
therapies and pharmacological treatment are recommended. Although different kinds of drugs have been studied for the treatment of
fibromyalgia, the most widely used drugs that have the higher degree of evidence for efficacy include the α(2)δ
ligands pregabalin and
gabapentin, and the
tricyclic antidepressants (TCAs) and
serotonin noradrenaline (
norepinephrine) reuptake inhibitors (
SNRIs). However, there is a need to look for newer additional therapeutic pharmacological options for the treatment of this complex and disabling disease. First- and second-generation
antipsychotics have shown
analgesic properties both in an experimental setting and in humans, although most of the available evidence for the treatment of human
pain concerns older
antipsychotics and involves clinical trials performed several decades ago. In addition, several second-generation
antipsychotics,
risperidone,
olanzapine and
quetiapine, have shown efficacy in the treatment of some
anxiety disorders. Some second-generation
antipsychotics, mainly
quetiapine,
aripiprazole and
amisulpride, have demonstrated
antidepressant activity, with
quetiapine approved for the treatment of
bipolar depression and refractory major depression, and
aripiprazole approved as an adjunctive treatment for
major depressive disorder. Finally, several old and new
antipsychotics, including
promethazine,
levopromazine,
olanzapine,
quetiapine and
ziprasidone, have been shown to improve sleep parameters in healthy subjects. Each of these properties suggests that
antipsychotics could represent a new potential alternative for the treatment of
fibromyalgia syndrome. To date, most of the published studies on the use of
antipsychotics in the treatment of
fibromyalgia syndrome have been uncontrolled, either case reports or case series, dealing with
olanzapine,
quetiapine,
ziprasidone,
levopromazine and
amisulpride. The studies on
olanzapine and
quetiapine have suggested therapeutic efficacy although, in the case of
olanzapine, hampered by tolerability problems. A double-blind controlled trial, published in 1980, showed that
chlorpromazine increased slow-wave sleep and improved
pain and mood disturbances. More recently, four double-blind controlled studies have explored the efficacy of
quetiapine, either alone or as an add-on treatment, in
fibromyalgia management. None of these trials has yet been published, although two of them have been presented as congress communications, both of them suggesting that
quetiapine could be a potential alternative treatment for
fibromyalgia. In summary, the current available evidence suggests that at least some
antipsychotics, specifically
quetiapine, could be useful for the treatment of
fibromyalgia and that further studies on the efficacy of these compounds are worth pursuing.