Mirtazapine

Mirtazapine, sold under the brand names Remeron and Remeron SolTab, is an atypical tetracyclic antidepressant which is used primarily in the treatment of depression. In addition to its antidepressant properties, mirtazapine has anxiolytic, sedative, antiemetic, antihistamine, and appetite stimulant effects and is sometimes used in the treatment of anxiety disorders, insomnia, nausea and vomiting, and to aid weight gain when desirable. It is taken by mouth.

Theory
Mirtazapine may be effective for some symptoms of ME/CFS or fibromyalgia or for co-existing conditions.

Evidence
The IACFS/ME Primer (2014) suggests mirtazapine for sleep dysfunction in ME/CFS with a dose of 7.5-15mg, but notes that daytime sleepiness and tolerance may occur. The Canadian Consensus Criteria and the International Consensus Primer do not suggest mirtazapine or recommend against it. 

A 2018 Cochrane review reported that mirtazapine is unlikely to substantially reduce pain in people with fibromyalgia. A small number of people may experience some improvement (moderate pain relief, better sleep). Specifically, mirtazapine reduced pain by 30% or more in five out of 10 people but it was not better than placebo in reducing fatigue, depression, or improving health‐related quality of life. They found no benefit of mirtazapine over placebo for pain relief of 50% or greater.

Off-label uses
In a recent Cochrane study fibromyalgia patients mirtazapine has been found to use a useful sleep aid for insomnia and other sleep problems.

Mirtazapine was also found reduce pain intensity, and to reduce pain by 30% in a significant number of patients. Mirtazapine was not found effective in reducing fibromyalgia pain by 50% and significant side effects occurred in some patients.

Side Effects
More commonly reported ones are: Less commonly reported ones are: Rare reactions: It is not known whether mirtazepine is safe for use in children.
 * Sleepiness including daytime, it is best takeb immediately before bed
 * Weight gain and appetite increase
 * Elevated alanine aminotransferase
 * Bone marrow problems, often presenting as granulocytopenia or agranulocytosis, although this is rare
 * severe skin reactions including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS)
 * Hyponatraemia - abnormally low sodium in the blood
 * Serotonin syndrome, which is a possible side effect in most antidepressants

Lactose
The mirtazapine brand contains small amounts of lactose.

Interactions

 * Increases sedation effects in other drugs e.g. most antipsychotics, antihistamine H1 antagonists, opioids) such as tramadol
 * Serotonin syndrome risks increase if taken with tryptophan, triptans, tramadol, linezolid, methylene blue, SSRIs antidepressants, venlafaxine, lithium and St. John's Wort (hypericum perforatum)
 * may increase the central nervous system depressant effects of alcohol (avoid alcohol)

Notable studies

 * 2017, Mirtazapine for fibromyalgia in adults (Abstract)

Learn more

 * Remeron - drugs.com