Norepinephrine-evoked pain in fibromyalgia. A randomized pilot study
[ISRCTN70707830].

BMC Musculoskelet Disord 2002;3(1):2

Martinez-Lavin M, Vidal M, Barbosa RE, Pineda C, Casanova JM,
Nava A.

Rheumatology Department Instituto Nacional de Cardiologia
Ignacio Chavez, Juan Badiano 1, 14080 Mexico D,F, Mexico.
mailto:mmlavin@infosel.net.mx

NLM Citation: PMID: 11860612

BACKGROUND: Fibromyalgia syndrome displays sympathetically maintained
pain features such as frequent post-traumatic onset and
stimuli-independent pain accompanied by allodynia and paresthesias. Heart
rate variability studies showed that fibromyalgia patients have changes
consistent with ongoing sympathetic hyperactivity. Norepinephrine-evoked
pain test is used to assess sympathetically maintained pain syndromes.
Our objective was to define if fibromyalgia patients have
norepinephrine-evoked pain.

METHODS: Prospective double blind controlled study.

Participants: Twenty FM patients, and two age/sex matched control groups;
20 rheumatoid arthritis patients and 20 healthy controls. Ten micrograms
of norepinephrine diluted in 0.1 ml of saline solution were injected in a
forearm. The contrasting substance, 0.1 ml of saline solution alone, was
injected in the opposite forearm. Maximum local pain elicited during the
5 minutes post-injection was graded on a visual analog scale (VAS).
Norepinephrine-evoked pain was diagnosed when norepinephrine injection
induced greater pain than placebo injection. Intensity of
norepinephrine-evoked pain was calculated as the difference between
norepinephrine minus placebo-induced VAS scores.

RESULTS: Norepinephrine-evoked pain was seen in 80 % of FM patients (95%
confidence intervals 56.3 -- 94.3%), in 30 % of rheumatoid arthritis
patients and in 30 % of healthy controls (95% confidence intervals 11.9
-- 54.3) (p < 0.05). Intensity of norepinephrine-evoked pain was greater
in FM patients (mean [plus minus] SD 2.5 [plus minus] 2.5) when compared
to rheumatoid arthritis patients (0.3 [plus minus] 0.7), and healthy
controls (0.3 [plus minus] 0.8) p < 0.0001.

CONCLUSIONS: Fibromyalgia patients have norepinephrine-evoked pain. This
finding supports the hypothesis that fibromyalgia may be a
sympathetically maintained pain syndrome.


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