Is mirtazapine (an antidepressant) considered an antipsychotic medication?

Is Mirtazapine an Antipsychotic?

No, mirtazapine is not an antipsychotic medication but rather a noradrenergic and specific serotonergic antidepressant (NaSSA) primarily used for the treatment of depression.

Classification and Mechanism of Action

Mirtazapine belongs to a distinct class of antidepressants with the following characteristics:

• It is classified as a noradrenergic and specific serotonergic antidepressant (NaSSA) 1
• It works by blocking presynaptic alpha-2 adrenergic receptors and postsynaptic serotonin type 2 and type 3 receptors 2
• Its antidepressant effect appears related to dual enhancement of central noradrenergic and serotonin 5-HT1 receptor-mediated serotonergic neurotransmission 3

Primary Indications

Mirtazapine is primarily indicated for:

• Treatment of major depression 1, 2
• Particularly effective in patients with depression and comorbid insomnia or anorexia 4

Differentiation from Antipsychotics

Guidelines clearly distinguish mirtazapine from antipsychotic medications:

1. In the NCCN Palliative Care guidelines, mirtazapine is specifically categorized as a "sedating antidepressant" separate from antipsychotic medications:

   • "For refractory insomnia, pharmacologic management includes the short-acting benzodiazepine lorazepam, the nonbenzodiazepine zolpidem, antipsychotic medications such as chlorpromazine, quetiapine, and olanzapine, and sedating antidepressants such as trazodone and mirtazapine." 4

2. In clinical practice guidelines for pain management, mirtazapine is categorized as a neuromodulator, not an antipsychotic:

   • "Neuromodulators with the most proven efficacy in the treatment of chronic pain are low-dose tricyclic antidepressants, serotonin noradrenergic reuptake inhibitors, and mirtazapine." 4

3. WHO guidelines specifically list antipsychotic medications separately from other psychiatric medications, with mirtazapine not included in the antipsychotic category 4

Medication Classification Tables

Medical guidelines consistently classify mirtazapine as an antidepressant, not an antipsychotic:

• In a comprehensive table of medications associated with weight changes, mirtazapine is listed under "Antidepressants" rather than "Antipsychotics" 4

Potential Confusion

The confusion might arise because:

1. Mirtazapine has been studied as an adjunctive treatment to antipsychotics in schizophrenia:

   • Research shows it may enhance the effect of first-generation antipsychotics when used in combination 5
   • However, this does not make mirtazapine itself an antipsychotic

2. Mirtazapine has sedating properties that might be confused with the sedative effects of some antipsychotics:

   • It causes significant sedation, especially at lower doses (7.5-15mg) 6
   • This sedating effect is due to its H1 receptor antagonism, not antipsychotic properties 6

Clinical Applications Beyond Depression

While not an antipsychotic, mirtazapine has been studied for other psychiatric conditions:

• Anxiety disorders (including PTSD, panic disorder, social anxiety disorder)
• Obsessive-compulsive disorder
• Somatoform disorders
• As add-on therapy in schizophrenia (but not as a primary antipsychotic) 1, 7

In conclusion, mirtazapine is definitively classified as an antidepressant with sedating properties, not an antipsychotic medication, according to established clinical guidelines and pharmacological classification systems.