Patients with fibromyalgia they present many more adverse effects to different drugs than other patients, although it is not known whether it is due to a symptom of the disease, for some psychological reason, or because of its central sensitization. In fact, it has been shown that "the number of dropouts due to adverse reactions in those affected with fibromyalgia treated with placebo it is double that in other pathologies ", according to a study carried out by Dr. Cayetano Alegre, of the Rheumatology Service of the Vall d'Hebrón University Hospital and the Dexeus University Institute, in Barcelona, ​​and which has been recently presented as oral communication in the EULAR Congress (European League against Rheumatic Diseases) 2011, held in London (United Kingdom).

A systematic review was made of the clinical trials that used placebo in order to explain the dropouts and the percentage of adverse effects in the three only drugs (Duloxetine, Milnacipran and Pregabalin) that have been approved by the North American Drug Agency to treat the fibromyalgia, but that are also indicated for other diseases.

In the opinion of the expert, "nocebo effect it is the harmful consequence of placebo (which is a comparative drug to another supposedly effective and that theoretically is harmless) in any clinical trial. In these studies there is always a percentage of patients who present benefits with this drug -placebo-, which can sometimes reach 34% of the population, but there is a group of patients who have adverse effects with placebo ".

Very prevalent nocebo effect

Specifically, clinical trials -of about ten weeks duration- were analyzed for the indication of fibromyalgia, anxiety, depression and neuropathic pain (DNP) separately. The average number of patients in the fibromyalgia group treated with placebo who dropped out due to adverse effects was 10.8%; while in the other entities it was 6.7% for the anxiety disorder, 4.4% for the depression and 4.5% for the DNP. Likewise, the mean number of patients with fibromyalgia treated with placebo who suffered at least one adverse effect was 77.4%.

The high percentage of nocebo effect in fibromyalgia could be associated with the presence of anxiety and / or depression in this syndrome

According to the research, the nocebo effect is very prevalent in fibromyalgia, similar to that of anxiety and depression, and significantly higher than that of DNP. "This fact suggests that the high percentage of this effect in fibromyalgia could be associated with the presence of anxiety or depression in this syndrome. The frequency of treatment discontinuations in the placebo groups due to adverse effects is much higher in fibromyalgia than in the other three pathologies, "the rheumatologist has confirmed.

In the opinion of Dr. Alegre, "possibly the presence of these side effects could be linked to the mood disorder that these patients present, to depression or anxiety. Although, the much higher number of dropouts in fibromyalgia makes us suspect a special sensitivity, possibly linked to the central sensitization they have ".

Source: Spanish Society of Rheumatology (SER)

The Fibromyalgia Seminar (November 2019).