What the FDA labels say about taking them together
Morphine and quinidine
Morphine's FDA label of July 13, 2026 names quinidine in its drug interactions section, and quinidine's label names morphine too. The morphine label: “The concomitant use of P-gp inhibitors can increase the exposure to morphine by two-fold and can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death.”
Check it at the source: the morphine FDA label on DailyMed (effective July 13, 2026, Bryant Ranch Prepack); the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.).
What does the morphine label say about quinidine?
Morphine label, drug interactionsP-Glycoprotein (P-gp) Inhibitors Clinical Impact: The concomitant use of PGP-inhibitors can increase the exposure to morphine by about two-fold and can increase risk of hypotension, respiratory depression, profound sedation, coma, and death. Intervention: Evaluate patients for signs of respiratory depression that may be greater than otherwise expected and decrease the dosage of morphine sulfate and/or the PGP-inhibitor as necessary. Example: Quinidine
Morphine Sulfate label (Hikma Pharmaceuticals USA Inc., February 3, 2026), drug interactionsP-Glycoprotein (P-gp) Inhibitors Clinical Impact: The concomitant use of P-gp inhibitors can increase the exposure to morphine by two-fold and can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death. Intervention: Evaluate patients for signs of respiratory depression that may be greater than otherwise expected and decrease the dosage of Morphine Sulfate Oral Solution and/or the P-gp inhibitor as necessary. Examples: Quinidine, verapamil.
Source: FDA drug label (Morphine Sulfate, NDA022195), Hikma Pharmaceuticals USA Inc., effective February 3, 2026 (SPL set ca359246-4674-4b32-b8b2-673d32b7112f), via openFDA
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
What does the quinidine label say about morphine?
Quinidine label, drug interactionsIn the case of prodrugs whose actions are actually mediated by P450 IID6 -produced metabolites (for example, codeine and hydrocodone, whose analgesic and antitussive effects appear to be mediated by morphine and hydromorphone, respectively), it may not be possible to achieve the desired clinical benefits in poor metabolizers.
Source: FDA drug label (Quinidine Gluconate), Sun Pharmaceutical Industries, Inc., effective February 1, 2018 (SPL set 5023f053-fcc4-4c2c-aa59-9ec198ad185e), 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
| Morphine | Quinidine | |
|---|---|---|
| Labeled for | Pain | Atrial fibrillation |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.226 per tablet 15 mg tablet | $4.92 per tablet 324 mg tablet |
| Shortage now | In shortage | 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