Carbachol and Acetaminophen And Codeine: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jun 30, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Acetaminophen And Codeine
Carbachol
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
You've been given two medicines: acetaminophen with codeine (a pain reliever that contains an opioid) and carbachol (usually eye drops or an eye medicine used in glaucoma or surgery). Codeine can make you feel sleepy or slow. The concern here is that carbachol might add a little to that drowsy, sluggish feeling.
The good news is this is a theoretical concern, meaning it hasn't clearly been shown to cause problems, especially since carbachol is mostly used in the eye. Just be aware of how you feel, and let your pharmacist or doctor know if you feel unusually drowsy or foggy. They can easily help you manage this.
Effect: Theoretical additive CNS depression when carbachol is combined with the codeine (opioid) component of acetaminophen/codeine.
- Mechanism: Additive CNS depressant effects (PD interaction). Codeine is a prodrug activated by CYP2D6 to morphine, but this interaction is pharmacodynamic, not metabolic.
- Direction/magnitude: Potentially enhanced sedation; magnitude unquantified and likely minimal given carbachol's predominantly ophthalmic/local use and low systemic exposure.
- Onset: Unspecified.
- Evidence: Theoretical.
- Management: Monitor for excess sedation/CNS depression; individualize opioid dosing and counsel on drowsiness.
What happens
An increased risk of CNS depression
Interaction Deep Dive
Coadministration of carbachol with CNS depressants may cause additive CNS effects1.
Why it happens (mechanism)
Additive CNS depression
How to manage this interaction
Keep taking both medicines as prescribed unless your care team tells you otherwise. This is a theoretical concern, and your team can manage it.
- Watch for signs of too much sedation, such as unusual drowsiness, confusion, or feeling very slowed down.
- Your opioid dose may need to be adjusted and individualized by your care team, and they may monitor you more closely if needed.
- Avoid other things that add drowsiness (like alcohol) unless cleared by your provider.
- Ask your pharmacist or doctor before starting or stopping either medicine.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Carbachol and Acetaminophen And Codeine together?
Combining carbachol with the codeine in acetaminophen/codeine could theoretically add to drowsiness, so watch for extra sedation and tell your care team if you feel unusually sleepy or foggy. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Carbachol and Acetaminophen And Codeine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Carbachol and Acetaminophen And Codeine interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. This is a theoretical concern, and your team can manage it. Watch for signs of too much sedation, such as unusual drowsiness, confusion, or feeling very slowed down. Your opioid dose may need to be adjusted and individualized by your care team, and they may monitor you more closely if needed. Avoid other things tha… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Carbachol or Acetaminophen And Codeine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Product Information: YUVEZZI™ ophthalmic solution, carbachol brimonidine tartrate 2.75%/0.1% ophthalmic solution. Visus Therapeutics Inc. (per FDA), Seattle, WA, 2026. DailyMed
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