Codeine Interactions Hub

Codeine Drug Interactions

Codeine is an opioid pain reliever that interacts with many common medicines. This page covers the most important combinations to know about — and links you to a plain-English explanation of each one.

Codeine interacts with many common medicines — especially antidepressants, benzodiazepines, sleep medicines, gabapentinoids, and other opioids. The two biggest risks are serotonin syndrome (with antidepressants) and respiratory depression (with sedatives). Always tell your doctor and pharmacist every medication you take before adding codeine.

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How does codeine interact with other medicines?

Codeine itself is a relatively weak opioid — but your liver converts a small amount of it into morphine via an enzyme called CYP2D6. That conversion is what gives codeine its pain-relieving effect. Two things can go wrong:

  • Some medicines block CYP2D6 — including SSRIs like sertraline, fluoxetine, and paroxetine — so codeine doesn't work as well, and the medicines that don't get converted can build up.
  • Other medicines add to codeine's sedating effects — including benzodiazepines, gabapentinoids, other opioids, and alcohol — increasing the risk of slowed breathing and accidental overdose.

Codeine and antidepressants

This is the most common high-risk combination. SSRIs and SNRIs inhibit CYP2D6 and add serotonin syndrome risk. Tricyclics and mirtazapine add sedation.

Codeine and benzodiazepines or sleep medicines

Combining codeine with any benzodiazepine or "Z-drug" sleep aid significantly increases the risk of respiratory depression. The FDA and TGA both carry boxed warnings on these combinations.

Codeine and other CNS-active medicines

Gabapentinoids, antipsychotics, and muscle relaxants all add to codeine's sedating effects.

What painkillers are safer if I take antidepressants?

If codeine isn't a good option for you, see our drug-specific safe painkiller guides:

Frequently asked questions

Can you take codeine with antidepressants?

It depends on the antidepressant. SSRIs and SNRIs (sertraline, escitalopram, fluoxetine, venlafaxine, duloxetine) inhibit the CYP2D6 enzyme that converts codeine into its active form, morphine — so codeine may be less effective for pain AND can cause serotonin syndrome. Tricyclics (amitriptyline, doxepin) and mirtazapine add sedation and respiratory depression risk. Always check with your doctor or pharmacist before combining.

What happens if you take codeine and sertraline together?

Sertraline (an SSRI) blocks the CYP2D6 enzyme that converts codeine into morphine, which is what gives codeine its pain-relieving effect. This means codeine may not work as well, AND combining the two raises the risk of serotonin syndrome — a serious condition causing agitation, rapid heart rate, fever, muscle stiffness, and confusion. The combination is rated moderate-to-major severity in clinical guidelines.

Can you take codeine with Valium or other benzodiazepines?

This combination is high-risk. Codeine is an opioid and benzodiazepines (Valium, Xanax, Ativan, Serepax) are both CNS depressants. Combined, they significantly increase the risk of severe drowsiness, respiratory depression, coma, and overdose. The FDA, TGA, and MHRA all carry boxed warnings about combining opioids with benzodiazepines. Talk to your prescriber before taking both.

Is it safe to take codeine with Lyrica (pregabalin)?

Combining codeine with pregabalin or gabapentin increases the risk of respiratory depression and severe drowsiness. The MHRA and FDA have issued specific safety warnings about gabapentinoid–opioid combinations causing breathing difficulties and deaths. If you have been prescribed both, your doctor should monitor you closely.

What painkillers can I take instead of codeine if I am on antidepressants?

Paracetamol is usually the safest first-line option. NSAIDs like ibuprofen and naproxen can be used short-term but may interact with SSRIs (increased bleeding risk). Tramadol is NOT a safer substitute — it has the same CYP2D6 and serotonin issues as codeine. See our guide on safe painkillers with sertraline, quetiapine, and mirtazapine for specifics. Always talk to your pharmacist before starting any new pain medication.

Why is codeine prescription-only in Australia?

Since 1 February 2018, all codeine-containing products in Australia are Schedule 4 (Prescription Only). The TGA up-scheduled codeine due to evidence of widespread misuse, dependence, and codeine-related deaths. Products like Panadeine Forte (30 mg codeine + 500 mg paracetamol) can no longer be bought over the counter.

Related resources

Medical Disclaimer: This content is for informational purposes for claims professionals and care workers. It is not medical advice. Always consult a qualified healthcare professional for clinical decisions. Drug information is sourced from TGA, FDA, MHRA, PBS, NICE, and CDC databases and may not reflect the latest updates. AllMeds does not replace clinical judgement.