What the FDA labels say about taking them together
Metaxalone and mirtazapine
Metaxalone's FDA label of January 11, 2023 names mirtazapine in its drug interactions section; the mirtazapine label PlainMeds reads does not name metaxalone. The metaxalone label: “Serotonergic drugs include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, opioids …”
Check it at the source: the metaxalone FDA label on DailyMed (effective January 11, 2023, Amneal Pharmaceuticals of New York LLC); the mirtazapine FDA label on DailyMed (effective August 6, 2025, Organon LLC).
What does the metaxalone label say about mirtazapine?
Metaxalone label, drug interactionsDiscontinue metaxalone if serotonin syndrome is suspected. Examples of serotonergic drugs include: selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, opioids (particularly fentanyl, meperidine, and methadone), drugs that affect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue).
Metaxalone label, warningsSerotonergic drugs include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, opioids (particularly fentanyl, meperidine, and methadone), drugs that affect the serotonergic neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), and drugs that impair metabolism of serotonin (including monoamine oxidase (MAO) inhibitors, both those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue) (see PRECAUTIONS:
Source: FDA drug label (Metaxalone, NDA022503), INA Pharmaceutics Inc, effective February 3, 2026 (SPL set fc6de1a6-26aa-47ac-a5d2-bf127a6ca563), via openFDA
Source: FDA drug label (Metaxalone), Amneal Pharmaceuticals of New York LLC, effective January 11, 2023 (SPL set f06f2b96-3684-483c-89f7-6c9201fd4664), via openFDA; the full label on DailyMed
What does the mirtazapine label say about metaxalone?
Mirtazapine's label (effective August 6, 2025) does not name metaxalone in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (REMERON), Organon LLC, effective August 6, 2025 (SPL set 98ad1917-a094-44f5-a28f-a64a8cfcd887), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Metaxalone | Mirtazapine | |
|---|---|---|
| Labeled for | Muscle spasms and spasticity | Depression |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.452 per tablet 800 mg tablet | $0.063 per tablet 15 mg tablet |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once