Monoamine oxidase inhibitors (MAOIs) for fibromyalgia

This summary of a Cochrane review presents what we know from research about the effect of MAOIs for fibromyalgia (FM).

The review shows that in people with FM:

MAOIs may slightly improve pain and tender points in the short term compared to placebo. Of the MAOIs studied, pirlindole seems more effective than moclobemide.

We often do not have precise information about side effects and complications. This is particularly true for rare but serious side effects. The most frequent side effects seen in the studies included nausea and vomiting. However, MAOIs are known to have serious and potentially fatal interactions with a variety of foods and other medications.

What is fibromyalgia and what are MAOIs?

Fibromyalgia is a chronic condition characterised by generalised pains along with other problems such as sleep disturbances, fatigue and cognitive dysfunction. MAOIs are a certain type of antidepressants that are occasionally used to treat fibromyalgia symptoms. Other antidepressants such as tricyclic agents have demonstrated that they can help to relieve pain, tender points, fatigue and sleep disturbances in people with fibromyalgia, but there is a need to know if MAOIs might also help.

Best estimate of what happens to people with fibromyalgia who take MAOIs:

Pain (higher scores mean worse or more severe pain)

- People who took MAOIs rated their pain to be 1.45 points lower on a scale of 0 to 10 compared to people who took placebo.

Global assessment (by patient)

- People who took MAOIs showed no difference in their global assessment compared to people who took placebo.

Tender points

- People who took MAOIs had a lower tender point score and a lower number of tender points (-0.36 difference) than people who took placebo after four weeks.

Physical function

- No information about physical function was provided.

Sleep disturbance

- No information about sleep disturbance was provided.

Adverse events (nausea and vomiting)

- 16 more people out of 100 who took MAOIs (pirlindole) had nausea and vomiting.

- 18 people out of 100 who took MAOIs (pirlindole) had nausea and vomiting.

- 2 people out of 100 who took placebo had nausea and vomiting.

- No information regarding people who took moclobemide is available.

Discontinuation due to adverse events

- 4 more people out of 100 who took MAOIs stopped medication due to adverse events.

- 9 people out of 100 who took MAOIs stopped medication due to adverse events.

- 5 people out of 100 who took placebo stopped medication due to adverse events.

Authors' conclusions: 

Data suggest that the effectiveness of MAOIs for the treatment of FM symptoms is limited. Although we observed a moderate effect size on pain and a small one on tender points, these results should be taken with caution as they are only based on two studies with a small number of patients and inconsistent risk of bias among them.

Read the full abstract...
Background: 

Fibromyalgia (FM) syndrome is a chronic condition of unknown aetiology characterised by musculoskeletal pain that often co-exists with sleep disturbance, cognitive dysfunction and fatigue. Patients often report high disability levels and poor quality of life. Since there is no specific treatment that alters the pathogenesis of FM, drug therapy focuses on pain reduction and improvement of other bothersome symptoms.

Objectives: 

The objective of this review was to assess the effectiveness and safety of monoamine oxidase inhibitors (MAOIs) in the treatment of FM syndrome.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 10), MEDLINE (1966 to November 2010), EMBASE (1980 to November 2010) and the reference lists of reviewed articles.

Selection criteria: 

We selected all randomised, double-blind trials of MAOIs used for the treatment of FM pain in adult participants.

Data collection and analysis: 

Two authors assessed risk of bias and extracted data independently onto a specially designed pro forma and a third review author cross-checked them.

Main results: 

We included two studies of inconsistent risk of bias with a total of 230 patients diagnosed with FM. We evaluated two MAOIs: pirlindole and moclobemide. Pirlindole showed statistically significant results compared with placebo for several outcomes (pain, tender points and overall assessment by the patient and the physician), whereas moclobemide did not show statistically significant differences between groups. Pooled results of the two studies displayed a modest effect size in pain (mean difference (MD) -1.45 (121 patients; 95% confidence interval (CI) -2.71 to -0.20; number needed to treat (NNT) 2 (95% CI 1 to 12); I2 = 59%)), implying a minimal clinically important difference (MCID) and a small effect on tender points (standardised mean difference (SMD) -0.36 (121 patients; 95% CI -0.72 to -0.00; I2 = 31%)). No effect was seen on global assessment by patient. Physical function and sleep disturbance were not measured. The most frequent adverse events were nausea and vomiting, with statistically significant differences between groups (risk ratio (RR) 7.82 (89 patients; 95% CI 1.02 to 59.97; NNT 7 (95% CI 4 to 33)).

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