Doxepin 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
Doxepin
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.
Your pain medicine contains codeine, and you're also taking doxepin. There are a few things worth knowing here. Codeine is a prodrug, meaning your body has to turn it into morphine to relieve pain. Doxepin can slow that step, so you might get less pain relief from the codeine than expected.
Both medicines can also make you very sleepy, cause constipation or trouble urinating, and (rarely) both affect a brain chemical called serotonin, which in unusual cases can cause agitation, sweating, and a racing heart. This is a theoretical concern, not something that happens to everyone. Keep taking both as prescribed, and your care team can adjust doses and watch you closely.
Direction: Doxepin is a CYP2D6 inhibitor. Codeine is a prodrug requiring CYP2D6 to form its active metabolite, morphine. Inhibition therefore reduces morphine formation (decreased analgesia, possible withdrawal) while increasing parent codeine exposure.
- Additive CNS depression: sedation, respiratory depression.
- Additive anticholinergic effect: urinary retention, severe constipation, risk of paralytic ileus.
- Serotonergic risk: potential serotonin syndrome (theoretical).
Evidence: theoretical. Severity: major. Onset: unspecified.
Management: Monitor for withdrawal, inadequate analgesia, retention/constipation, serotonin syndrome, and respiratory depression during initiation and dose changes. Consider dose reduction of doxepin and/or codeine per response. Discontinue codeine if serotonin syndrome is suspected.
What happens
An increased risk of paralytic ileus, an increased risk of serotonin syndrome, an increased codeine exposure, reduced active metabolite (morphine) exposure and an increased risk of CNS depression
Interaction Deep Dive
Concomitant use of codeine with doxepin (serotonergic drug with anticholinergic properties and a CYP2D6 inhibitor) may reduce exposure of morphine, the active metabolite of codeine, thus potentially leading to reduced efficacy and withdrawal symptoms, may increase the risk of urinary retention and severe constipation, which may lead to paralytic ileus and may increase the risk of serotonin syndrome. If concomitant use is needed, closely monitor the patient for withdrawal symptoms, urinary retention, severe constipation, signs and symptoms of serotonin syndrome and respiratory depression during treatment initiation and dose adjustment. Discontinue codeine if serotonin syndrome is suspected1. If concomitant use of doxepin with other serotonergic drugs is clinically warranted, inform patients of the increased risk for serotonin syndrome. Concomitant use of doxepin with codeine (CNS depressant) may also increase the risk of additive CNS depression which may potentiate sedative effects of CNS depressants. Dosage reduction of doxepin and/or the CNS depressant may be needed based on clinical response and tolerability 2.
Why it happens (mechanism)
Additive effects on gastric motility; additive serotonergic effects; inhibition of CYP2D6-mediated metabolism of codeine; additive CNS depression
How to manage this interaction
You can usually take both when your prescriber has planned for it. Here is what typically happens:
- Your care team may adjust and individualize the doses of one or both medicines based on how you respond.
- They may monitor you more closely, especially when starting or changing a dose.
Keep taking both as prescribed. Call your pharmacist or doctor if you notice heavy sedation, slow or shallow breathing, severe constipation, trouble urinating, worse-than-expected pain, or agitation, sweating, tremor, and a fast heartbeat. Do not start, stop, or change either medicine on your own.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) The clinical features of serotonin syndrome can involve alterations in mental status (for example, agitation, hallucinations, delirium, and coma), autonomic instability (for example, tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular manifestations (for example, tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, and gastrointestinal effects (for example, nausea, vomiting, diarrhea) 2.
Common questions
Can I take Doxepin and Acetaminophen And Codeine together?
Doxepin can lower codeine's pain relief and add to drowsiness, constipation, and (rarely) serotonin effects, so let your care team tailor the doses and monitor you. Watch for heavy sedation, slow breathing, severe constipation, or poor pain control and report them. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Doxepin and Acetaminophen And Codeine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Doxepin and Acetaminophen And Codeine interaction managed?
You can usually take both when your prescriber has planned for it. Here is what typically happens: Your care team may adjust and individualize the doses of one or both medicines based on how you respond. They may monitor you more closely, especially when starting or changing a dose. Keep taking both as prescribed. Call your pharmacist or doctor if you notice heavy sedation, slow or shallow breathi… 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 Doxepin 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 a safer alternative to one of these medications for me?
References (2)
- Product Information: CARISOPRODOL, ASPIRIN, CODEINE PHOSPHATE oral tablets, carisoprodol, aspirin, codeine phosphate oral tablets. Ingenus Pharmaceuticals LLC (per DailyMed), Orlando, FL, 2021. DailyMed
- Product Information: SINEQUAN(R) oral capsules, oral solution, doxepin HCl oral capsules, oral solution. Pfizer Inc. (per FDA), New York, NY, 2025.
Keep reading about Acetaminophen And Codeine
Keep reading about Doxepin
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
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