Does Codeine Interact With Morphine?
Use 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.
Severity: Moderate
Severity basis: boxed warning (keywords: consider). Combining Codeine (Opioid analgesic) and Morphine (Opioid analgesic) is classified as a moderate interaction.
What to Do
Use this combination with caution. Your prescriber may monitor you more closely or adjust doses.
How This Interaction Works
Interactions like this one can happen when two medicines have overlapping effects, or when one changes how the other is absorbed, broken down, or cleared from the body. Codeine is a opioid analgesic and Morphine is a opioid analgesic; together they are documented as a moderate interaction. How much this matters depends on your dose, your other medications, and your overall health.
If You Take Both Medications
If you have been prescribed both Codeine and Morphine, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
From the FDA Label
Use 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.
Source: FDA structured product labeling (set_id 010905f9-3bcb-4b50-9fe8-a3ad0010f14c).
Check these against your full medication list in our free Interaction Checker
Frequently Asked Questions
Can you take Codeine and Morphine together?
Codeine and Morphine have a documented moderate interaction. Use this combination with caution. Your prescriber may monitor you more closely or adjust doses.
How serious is the Codeine and Morphine interaction?
It is classified as a moderate interaction, based on the FDA label's boxed warning (keywords: consider). A moderate interaction can be clinically meaningful and usually calls for monitoring or a dose adjustment.
What should I do if I'm taking both Codeine and Morphine?
If you have been prescribed both Codeine and Morphine, do not start, stop, or change either medication on your own — some medicines are unsafe to stop suddenly. Tell your prescriber and pharmacist that you take both so they can decide whether the combination is right for you, adjust the dose, monitor you more closely, or suggest an alternative.
This information is educational — not medical advice.
This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.
Other Codeine Interactions
- Codeine + Buprenorphine Naloxone(major)
- Codeine + Hydrocodone Acetaminophen(moderate)
- Codeine + Ketoconazole(moderate)
- Codeine + Oxycodone(moderate)
- Codeine + Alprazolam(minor)
- Codeine + Amiodarone(minor)
- Codeine + Bupropion(minor)
- Codeine + Carbamazepine(minor)
- Codeine + Cyclobenzaprine(minor)
- Codeine + Fluoxetine(minor)
- Codeine + Gabapentin(minor)
- Codeine + Mirtazapine(minor)
- Codeine + Paroxetine(minor)
- Codeine + Phenytoin(minor)
- Codeine + Pregabalin(minor)
- Codeine + Rifampin(minor)
- Codeine + Tramadol(minor)
- Codeine + Trazodone(minor)
Other Morphine Interactions
- Morphine + Buprenorphine Naloxone(major)
- Morphine + Clopidogrel(moderate)
- Morphine + Gabapentin(moderate)
- Morphine + Ticagrelor(moderate)
- Morphine + Alprazolam(minor)
- Morphine + Cyclobenzaprine(minor)
- Morphine + Mirtazapine(minor)
- Morphine + Oxycodone(minor)
- Morphine + Rifampin(minor)
- Morphine + Tramadol(minor)
- Morphine + Trazodone(minor)
- Morphine + Verapamil(minor)