Impact of Antidepressant Mirtazapine on Symptoms of Fibromyalgia

Impact of Antidepressant Mirtazapine on Symptoms of Fibromyalgia

By: Dr Alex Robber

Fibromyalgia is a heterogenous condition

The definite (cause) aetiology of that syndrome remains unclear. This has proposed a model of interacting biological and psychosocial variables in the symptoms of fibromyalgia chronicity predisposition, triggering, and development.

Many causes are associated with fibromyalgia’s pathophysiology (functional changes associated with or resulting from disease), but the exact relationship to the disorder’s symptoms is uncertain. The best-established pathophysiological symptoms are those of central sensitisation; i.e., increased brain pain and sensory perception, increased functional connectivity to pro-nociceptive brain regions and reduced connectivity to antinociceptive regions, and subsequent changes in neurotransmitters of the central nervous system (CNS), as well as the size and shape of the brain regions.

What is Mirtazapine?

Mirtazapine facilitates noradrenaline and serotonin release by blocking, respectively, α2-adrenergic autoreceptors and α2-adrenergic heteroreceptors. This also stimulates neurotransmission of serotonin, primarily through 5-HT1A receptors, and blocks receptors of 5-HT2A, 5-HT2C and 5-HT3 postsynaptics.

Mirtazapine is graded as a noradrenergic and unique serotonergic antidepressant based on certain pharmacological mechanisms. Since mirtazapine raises the extracellular levels of noradrenaline and serotonin (a similar effect to serotonin–noradrenaline reuptake inhibitors and tricyclic antidepressants, but by different mechanisms), mirtazapine is expected to have analgesic effects and improve sleep disorders in FM patients.

A systematic review

Mirtazapine is commonly used for the treatment of major depressive disorder. It has been studied for potential benefits in patients with fibromyalgia because of its effects on multiple neurotransmitters. The aim of this systematic review is to evaluate the effectiveness and safety of mirtazapine in treating fibromyalgic patients.

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CENTRAL and were queried using a variation of the search term: fibromyalgia, pain, chronic pain, neuralgia, neuropathic pain, chronic widespread pain, or chronic pain syndrome and mirtazapine. Objective-appropriate studies were reviewed, including three randomized, placebo-controlled trials and one open-label trial, investigating the effect of mirtazapine in fibromyalgic patients.

Mirtazapine therapy in patients with fibromyalgia has led to changes in pain, sleep and quality of life. Test durations ranged from 6 to 13 weeks, and trials for mirtazapine used different dosing strategies. Minor cases of drowsiness, weight gain, nasopharyngitis, dry mouth and increased appetite with mirtazapine use were recorded.

Based on the literature reviewed, mirtazapine appears to be a promising treatment for improving pain, sleep and quality of life in fibromyalgic patients. Such effects have been shown in treatment-naïve patients and others who have failed prior therapies. More clinical research would be useful to better define the role of mirtazapine in patients with fibromyalgia through larger and longer-length trials.

It is an additional pharmacological therapeutic option

The Food and Drug Administration (FDA) has licensed the serotonin-norepinephrine reuptake antidepressant antagonists duloxetine and milnacipran but not the European Medicines Agency (EMA) for fibromyalgia. Both medications improve serotonin (5-hydroxytryptamine [5-HT]) and norepinephrine production in synaptic clefts of the CNS.

They have the ability to alleviate pain by restoring the functional deficiency in neurotransmission in 5-HT and norepinephrine in the inhibitory pain pathway that descends. Such antidepressants are successful in relieving one of the main symptoms of fibromyalgia, namely pain, but do not eliminate clinically significant sleep problems. Additional pharmacological therapeutic approaches are required to treat the main symptoms of fibromyalgia pain, sleep problems and fatigue.

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Mirtazapine (Remeron) as a potential treatment in treating fibromyalgia pain

The research focused on the medication mirtazapine (Remeron) as a possible cure for fibromyalgia pain relief. Mirtazapine is commonly used as an antidepressant, but the study showed a significant reduction in pain for patients with fibromyalgia who did not have depression.

Previous research on mirtazapine for fibromyalgia treatment found that the drug could be effective in treating not only the causes of pain fibromyalgia but also other symptoms of fibro, such as sleep disturbances and exhaustion. Researchers also found that mirtazapine works in a similar manner to duloxetine (a serotonin-noradrenaline reuptake inhibitor, already licensed for fibromyalgia treatment).

Purposes of this most recent study

The aim of this most recent mirtazapine research was to test the drug’s efficacy as a treatment for fibromyalgia at a fixed dose. The research has opted to avoid using patients that have shown signs of distress as mirtazapine are an antidepressant to prevent contradictory outcomes and this may cause possible bias.

The study was performed over a 12 week period and involved 430 patients with fibromyalgia. The patients were split into two groups, with half of the patients receiving for the first week a daily dose of mirtazapine of 15 mg and 30 mg for the remaining 11 weeks.

A placebo was given to the other half during the study. To monitor the impact of the medication on pain, each patient kept a daily pain log, rating their pain on a numerical score (NRS) of 0 to 10. A weekly NRS was calculated using these pain papers, and mean was determined at different time points for both the mirtazapine group and the placebo group.

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The study results showed a drop in mean NRS pain scores from week 2 through week 8 in the group of patients who received mirtazapine. Since week 8, this group kept the mean NRS pain scores steady. These findings showed a substantially greater drop in mean NRS pain scores for the mirtazapine group compared with those of the placebo group.


Participants can suffer severe adverse reactions. Serious adverse effects usually involve any unexpected medical condition or consequence that is life-threatening at any dosage, needs hospitalization or prolongation of ongoing hospitalization, results in permanent or serious impairment or incapacity, is a congenital disorder or birth defect, is a’ major medical incident’ that may jeopardize the person or may require an intermediate impairment.

Study Reference : PubMed

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