What the FDA labels say about taking them together
Codeine and morphine
Codeine's FDA label of December 22, 2025 names morphine in its boxed warning section; morphine's label does not name codeine itself but warns about its class (Opioids (opioid agonists)). The codeine label: “Codeine is metabolized by CYP2D6 to form morphine. The concomitant use of Codeine Sulfate Tablets and CYP2D6 inhibitors can increase the plasma concentration of codeine, but can decrease the plasma concentration of …”
Check it at the source: the codeine FDA label on DailyMed (effective December 22, 2025, Hikma Pharmaceuticals USA Inc.); the morphine FDA label on DailyMed (effective July 13, 2026, Bryant Ranch Prepack).
What does the codeine label say about morphine?
Codeine label, boxed warningUse of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with Codeine Sulfate Tablets requires careful consideration of the effects on the parent drug, codeine, and the active metabolite, morphine. [See Warnings and Precautions ( 5.7 ), Drug Interactions ( 7 )].
Codeine label, drug interactionsRifampin, carbamazepine, phenytoin Inhibitors of CYP2D6 Clinical Impact: Codeine is metabolized by CYP2D6 to form morphine. The concomitant use of Codeine Sulfate Tablets and CYP2D6 inhibitors can increase the plasma concentration of codeine, but can decrease the plasma concentration of active metabolite morphine, which could result in reduced analgesic efficacy or symptoms of opioid withdrawal … Intervention: If concomitant use with a CYP2D6 inhibitor is necessary, or if a CYP2D6 inhibitor is discontinued after concomitant use, consider dosage adjustment of Codeine Sulfate Tablets and evaluate patients at frequent intervals. …
Codeine label, warnings and precautionsCodeine is subject to variability in metabolism based upon CYP2D6 genotype (described below), which can lead to an increased exposure to the active metabolite morphine.
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 morphine label say about codeine?
Morphine's label does not name codeine itself; it warns about its class (Opioids (opioid agonists)):
Morphine label, warnings and precautionsLife-Threatening Respiratory Depression Serious, life-threatening, or fatal respiratory depression has been reported with the use of opioids, even when used as recommended.
Morphine label, boxed warningInstruct patients to swallow MS CONTIN tablets whole to avoid exposure to a potentially fatal dose of morphine. ( 5.2 ) Accidental ingestion of MS CONTIN, especially by children, can result in a fatal overdose of morphine. ( 5.2 ) Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death.
Source: FDA drug label (Morphine sulfate), ANDA078761 (Sun Pharm Inds Ltd), as published by Bryant Ranch Prepack, effective July 13, 2026 (SPL set 595243fe-a4b1-479a-99d6-a084a4181891), 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 | Morphine | |
|---|---|---|
| Labeled for | Pain | Pain |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.726 per tablet 30 mg tablet | $0.226 per tablet 15 mg tablet |
| Shortage now | No current entry | In shortage |
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