What the FDA labels say about taking them together
Dextromethorphan and methylene blue
Methylene blue's FDA label of May 28, 2025 names dextromethorphan in its drug interactions section; the dextromethorphan label PlainMeds reads does not name methylene blue. The methylene blue label: “Opioids and dextromethorphan may increase the risk of developing serotonin syndrome.”
Check it at the source: the dextromethorphan FDA label on DailyMed (effective August 27, 2026); the methylene blue FDA label on DailyMed (effective May 28, 2025, American Regent, Inc.).
What does the dextromethorphan label say about methylene blue?
Dextromethorphan's label (effective August 27, 2026) does not name methylene blue in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Good Sense Cough DM), L. Perrigo Company, effective August 27, 2026 (SPL set 5a2e9bef-42cb-4b72-9a26-c3ae71dcb4ea), via openFDA; the full label on DailyMed
What does the methylene blue label say about dextromethorphan?
Methylene blue label, drug interactionsAvoid concomitant use of PROVAYBLUE with medicinal products that enhance serotonergic transmission including antidepressants like SSRIs (selective serotonin reuptake inhibitors), SNRIs (serotonin and norepinephrine reuptake inhibitors), MAOIs (monoamine oxidase inhibitors), bupropion, buspirone, clomipramine, mirtazapine, linezolid, opioids, and dextromethorphan because of the potential for serious CNS reactions, including potentially fatal serotonin syndrome.
Methylene blue label, warnings and precautionsOpioids and dextromethorphan may increase the risk of developing serotonin syndrome.
Source: FDA drug label (PROVAYBLUE), NDA204630 (Provepharm Sas), as published by American Regent, Inc., effective May 28, 2025 (SPL set 4f6848e5-35ed-4046-b13c-3032b5ba3232), 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
| Dextromethorphan | Methylene blue | |
|---|---|---|
| Labeled for | Cough and cold | n/a |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.122 per unit 15 mg softgel | n/a |
| 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