What the FDA labels say about taking them together
Codeine and methylene blue
Codeine's FDA label of December 22, 2025 names methylene blue in its drug interactions section; methylene blue's label does not name codeine itself but warns about its class (Opioids (opioid agonists)). The codeine label: “The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.”
Check it at the source: the codeine FDA label on DailyMed (effective December 22, 2025, Hikma Pharmaceuticals USA Inc.); the methylene blue FDA label on DailyMed (effective May 28, 2025, American Regent, Inc.).
What does the codeine label say about methylene blue?
Codeine label, drug interactionsSerotonergic Drugs Clinical Impact: The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. … inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue).
Source: FDA drug label (Codeine sulfate), Hikma Pharmaceuticals USA Inc., effective December 22, 2025 (SPL set 010905f9-3bcb-4b50-9fe8-a3ad0010f14c), via openFDA; the full label on DailyMed
What does the methylene blue label say about codeine?
Methylene blue's label does not name codeine itself; it warns about its class (Opioids (opioid agonists)):
Methylene blue label, boxed warningSEROTONIN SYNDROME WITH CONCOMITANT USE OF SEROTONERGIC DRUGS AND OPIOIDS PROVAYBLUE may cause serious or fatal serotonergic syndrome when used in combination with serotonergic drugs and opioids.
Methylene blue label, boxed warningSEROTONIN SYNDROME WITH CONCOMITANT USE OF SEROTONERGIC DRUGS AND OPIOIDS See full prescribing information for complete boxed warning.
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
| Codeine | Methylene blue | |
|---|---|---|
| Labeled for | Pain | n/a |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.726 per tablet 30 mg tablet | 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