What the FDA labels say about taking them together
Metaxalone and nalbuphine
Nalbuphine's FDA label of December 31, 2025 names metaxalone in its drug interactions section; the metaxalone labels PlainMeds reads (2) do not name nalbuphine. The nalbuphine label: “Serotonergic Drugs The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system, such as selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake …”
Check it at the source: the metaxalone FDA label on DailyMed (effective January 11, 2023, Amneal Pharmaceuticals of New York LLC); the nalbuphine FDA label on DailyMed (effective December 31, 2025, Hospira, Inc.).
What does the metaxalone label say about nalbuphine?
Metaxalone's label (effective January 11, 2023) and its 1 other brand-application label do not name nalbuphine in these sections. A label lists what its studies and reports found; it is not a complete list.
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 nalbuphine label say about metaxalone?
Nalbuphine label, drug interactionsSerotonergic Drugs The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system, such as selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that effect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), and monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue), has resulted in serotonin syndrome [see PRECAUTIONS;
Source: FDA drug label (Nalbuphine Hydrochloride), Hospira, Inc., effective December 31, 2025 (SPL set 6025e8d4-5083-4c3a-58a0-050e7b0b6150), 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 | Nalbuphine | |
|---|---|---|
| Labeled for | Muscle spasms and spasticity | Pain |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.452 per tablet 800 mg tablet | $4.32 per mL 10 mg/mL ampul |
| 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