RESEARCH MONOGRAPH · KDC-MN-214

Mianserin

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 2 min read

Our opinion on this compound

65/100

The original tetracyclic. Eclipsed by mirtazapine but pharmacologically meaningful in its own right

Mianserin is the original tetracyclic antidepressant from Organon's research program in the 1970s, and it's the structural and pharmacological parent of mirtazapine. Approved in Europe in 1976 but never reached the US market, which is one of those regulatory quirks that obscures real pharmacology from American researchers. It's still used clinically in much of Europe, particularly the UK and Japan.

Mechanism is similar to mirtazapine but with somewhat different receptor binding ratios. Alpha-2 adrenergic antagonism is the primary action, with significant 5-HT2A, 5-HT2C, and H1 antagonism. The 5-HT3 antagonism that contributes to mirtazapine's GI tolerability is weaker, which is partly why mianserin has more nausea reports than mirtazapine in comparative trials. The compound binds essentially nothing at SERT or NET.

The clinical efficacy data is solid for MDD, though older trials and less head-to-head data against modern SSRIs than for mirtazapine. The Cipriani 2018 meta-analysis included mianserin and put it roughly mid-pack for both efficacy and acceptability, with weight gain and sedation as the dominant tolerability issues, similar to mirtazapine but in different proportions.

What's genuinely interesting historically: mianserin was associated with a rare but real risk of agranulocytosis at clinical doses, which is part of why it never reached the US market and why Organon developed mirtazapine as a successor with a cleaner hematological profile. The agranulocytosis signal in the 80s and 90s was small (probably less than 1 in 1000 cases) but consistent enough that monitoring was recommended in countries where mianserin was prescribed. Mirtazapine effectively replaced it.

For research applications mianserin remains useful as a tool compound for alpha-2 antagonism studies and for the broader tetracyclic pharmacology. It's somewhat more selective for alpha-2 than mirtazapine and has been used in animal models of stress-induced cognitive impairment, anxiety, and noradrenergic modulation. The receptor profile is well-characterized in the older literature.

Sourcing for research material is workable but less commercially abundant than for mirtazapine. Reference standards exist but are less commonly stocked. For most antidepressant research mirtazapine is the better choice. For specific alpha-2 antagonism work or for comparative pharmacology with mirtazapine, mianserin has its place. Honestly more interesting historically than the limited US familiarity suggests.

Evidence: 72
Mechanism: 82
Reliability: 68
Safety: 60
Sourcing: 65
Value: 65
Signal: 50
Staying power: 55

Plain-language summary Intrigue 47 / 100

Mianserin is the older European cousin of mirtazapine, developed at Organon in the 1960s and marketed across Europe and Asia from 1976 onward. It was never approved in the United States. Like mirtazapine it boosts norepinephrine and serotonin output by blocking the auto-brake on those neurons rather than blocking the reuptake pumps. The differences are subtle: mianserin has a wider spread of off-target receptor activity and a small but historically significant risk of bone marrow suppression, which is part of why mirtazapine ultimately replaced it in most markets. Mianserin remains useful as a research tool for understanding the alpha-2 adrenergic receptor mechanism. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Tetracyclic alpha-2 adrenergic antagonist

A first-generation tetracyclic antidepressant; the structural and mechanistic precursor to mirtazapine.

Abstract

Mianserin (1,2,3,4,10,14b-hexahydro-2-methyldibenzo[c,f]pyrazino[1,2-a]azepine; CAS 24219-97-4; molecular formula C18H20N2; molecular weight 264.37) is a tetracyclic antidepressant developed at Organon in the 1960s and marketed in Europe and Asia from 1976 (never FDA approved for the US market). The compound is the structural and mechanistic precursor to mirtazapine, sharing the alpha-2 adrenergic auto/heteroreceptor antagonism that increases monoaminergic release. Mianserin additionally exhibits 5-HT2A, 5-HT2C, H1, and alpha-1 antagonism but with a less favorable receptor selectivity profile than mirtazapine. Notable for a higher incidence of agranulocytosis and aplastic anemia than mirtazapine (estimated 1 in 1500 to 1 in 5000 cases) which contributed to its replacement in clinical practice. Plasma half-life is 21 to 61 hours; metabolism is via CYP2D6 with active demethyl-mianserin metabolite. Used as a reference tetracyclic and alpha-2 antagonist in mechanism studies; less common in clinical use today owing to mirtazapine availability.

Mechanism of action

Alpha-2 adrenergic auto/heteroreceptor antagonism, 5-HT2A/2C antagonism, H1 antagonism. Structural precursor to mirtazapine with broader off-target profile.

Reported research dose ranges

Reported research dose ranges in the literature.

References

de Jonghe F, Swinkels JA. The safety of mianserin. Drug Saf 1992.
Pinder RM, van Delft AM. The potential therapeutic role of the enantiomers of mianserin. Br J Pharmacol 1983.
Brogden RN, et al. Mianserin: a review of its pharmacological properties and therapeutic efficacy in depressive illness. Drugs 1978.

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KDC-MN-214

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

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Mianserin

Abstract

Mechanism of action

Reported research dose ranges

References

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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