Pain and depression drugs not working? Antidepressants can interfere with opioids
Pharmacists have long known that some pain and depression medications do not work well together. Certain common antidepressants can greatly reduce the pain relief from some opioid painkillers. In a study of 4,306 surgical patients with depression, people taking an SSRI antidepressant together with a "prodrug" opioid, one that must be activated in the liver, had worse pain control at discharge and up to 8 weeks after surgery than people taking an SSRI with an opioid that works directly. Understanding your genes and your medications can help lower this risk.
Why don't some pain and depression drugs work together?
People with depression often live with pain as well, and finding treatment that works for both can be hard. A common reason is a drug-gene-drug interaction: the antidepressant, the painkiller and your genes all involve the same liver enzyme, CYP2D6.
Several common painkillers are "prodrugs". They do little until CYP2D6 converts them into a stronger form: codeine (in Tylenol 3) becomes morphine, tramadol becomes O-desmethyltramadol, and hydrocodone is partly converted into hydromorphone.
Which antidepressants block CYP2D6?
Some antidepressants block CYP2D6, so less of the active painkiller is made. The 2023 CPIC guideline describes paroxetine and fluoxetine as potent CYP2D6 blockers. Other antidepressants block it less:
| Effect on CYP2D6 | Antidepressants |
|---|---|
| Strong blockers | Paroxetine (Paxil), fluoxetine (Prozac), bupropion (Wellbutrin) |
| Moderate blocker | Duloxetine (Cymbalta) |
| Weak blockers | Sertraline (Zoloft), citalopram (Celexa), escitalopram (Cipralex), fluvoxamine (Luvox) |
The 2021 CPIC opioid guideline advises that people taking a strong CYP2D6 blocker be treated as poor metabolizers, even if their genes are normal.
Which painkillers are affected?
| Painkiller | How CYP2D6 matters |
|---|---|
| Codeine (Tylenol 3) | Must be converted into morphine. Strongly affected by CYP2D6 blockers and genes. |
| Tramadol | Must be converted into its active form. Strongly affected by CYP2D6 blockers and genes. |
| Hydrocodone | Partly converted into hydromorphone. Pain relief may be reduced, but the evidence is limited. |
| Oxycodone (Percocet, OxyContin) | Works mostly as it is. No gene-based dose change is recommended. |
| Morphine, hydromorphone | Do not depend on CYP2D6. |
This is why the study above suggested that directly acting opioids, such as oxycodone or morphine, may be a better choice for people taking SSRIs.
A safety warning about stopping or switching antidepressants
If the opioid dose is raised to make up for poor pain relief while a CYP2D6-blocking antidepressant is being taken, problems can follow when that antidepressant is stopped or switched. Once the block is lifted, more of the opioid is turned into its active form, which can cause dangerous sleepiness and slowed breathing. Tramadol taken with SSRIs or SNRIs also raises the risk of serotonin syndrome, and in a large study, people newly prescribed tramadol had higher rates of death, heart problems and fractures than people prescribed codeine. Never stop, start or switch these medications without talking to your doctor or pharmacist.
How your genes add to the risk
CYP2D6 activity also depends on your DNA. According to the CPIC opioid guideline:
- Ultrarapid metabolizers turn codeine and tramadol into their active forms too quickly, which can cause serious toxicity even at normal doses. They should avoid codeine and tramadol.
- Intermediate metabolizers can take the usual dose but should be watched, and switched to another painkiller if pain relief is poor. A CYP2D6-blocking antidepressant can push them further toward poor metabolism.
- Poor metabolizers get little or no relief from codeine and tramadol and should avoid them.
For ultrarapid and poor metabolizers, non-opioid painkillers or opioids not affected by CYP2D6, such as morphine or hydromorphone, are alternatives. Long-term use of stronger opioids carries a risk of dependence, so the choice depends on the type and length of pain. Learn more in Tylenol 3 Side Effects: Why Codeine Doesn't Work for Everyone.
Antidepressants that can also help with pain
Some antidepressants can also treat chronic pain. Tricyclic antidepressants such as amitriptyline and nortriptyline can help with both pain and depression. At the low doses used for pain, the CPIC guideline for tricyclics recommends no dose change for CYP2D6 or CYP2C19 poor or intermediate metabolizers, with monitoring for side effects, while CYP2D6 ultrarapid metabolizers may need another medication. Some SNRIs, such as duloxetine, can also help with chronic pain. Desvenlafaxine is broken down by CYP3A4 rather than CYP2D6, so CYP2D6 results do not affect it. Learn more in Most effective treatments for fibromyalgia.
Sertraline, citalopram and escitalopram are broken down mainly by another enzyme, CYP2C19, and block CYP2D6 only weakly. For people with two copies of the CYP2C19*17 variant (ultrarapid metabolizers), CPIC recommends considering another antidepressant for citalopram and escitalopram, while people with one copy can usually start at the usual dose. Learn more in Comparison of antidepressants' effectiveness and side effects.
How can a pharmacogenetic test help?
If your pain and depression medications are not working well together, a pharmacogenetic test such as Pillcheck can show your CYP2D6 and CYP2C19 metabolizer types. Pillcheck includes a medication review by a clinical pharmacist, who checks for drug interactions and recommends to your doctor how to adjust your pain and depression medications.
Summary
- Some antidepressants, especially paroxetine, fluoxetine and bupropion, block CYP2D6 and can stop codeine and tramadol from relieving pain.
- Oxycodone, morphine and hydromorphone are less affected or not affected by CYP2D6.
- Stopping or switching a CYP2D6-blocking antidepressant while taking codeine or tramadol can raise opioid levels, so changes should be supervised.
- Your CYP2D6 genes add to these effects, and a pharmacogenetic test with a pharmacist review can help your doctor choose safer combinations.
Frequently asked questions
Can antidepressants stop painkillers from working?
Yes. Antidepressants that block CYP2D6, such as paroxetine, fluoxetine and bupropion, can reduce the pain relief from codeine, tramadol and possibly hydrocodone.
Which painkillers work better with these antidepressants?
Painkillers that do not depend on CYP2D6, such as oxycodone, morphine and hydromorphone, or non-opioid painkillers. Your doctor will choose based on your pain and other medications.
Is it safe to take tramadol with an SSRI?
It needs caution. The SSRI may reduce tramadol's pain relief, and the combination raises the risk of serotonin syndrome. Talk to your doctor or pharmacist.
Can I stop my antidepressant if my pain medication is not working?
Not on your own. Stopping or switching suddenly can cause withdrawal symptoms and can raise opioid levels if you are taking codeine or tramadol. Talk to your doctor or pharmacist first.
Selected references
Parthipan A, Banerjee I, Humphreys K, et al. Predicting inadequate postoperative pain management in depressed patients: A machine learning approach. PLoS One. 2019;14(2):e0210575.
Crews KR, Monte AA, Huddart R, et al. Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2D6, OPRM1, and COMT Genotypes and Select Opioid Therapy. Clin Pharmacol Ther. 2021;110(4):888-896.
Bousman CA, Stevenson JM, Ramsey LB, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2D6, CYP2C19, CYP2B6, SLC6A4, and HTR2A Genotypes and Serotonin Reuptake Inhibitor Antidepressants. Clin Pharmacol Ther. 2023;114(1):51-68.
Hicks JK, Sangkuhl K, Swen JJ, et al. Clinical Pharmacogenetics Implementation Consortium guideline (CPIC) for CYP2D6 and CYP2C19 genotypes and dosing of tricyclic antidepressants: 2016 update. Clin Pharmacol Ther. 2017;102(1):37-44.
Xie J, Strauss VY, Martinez-Laguna D, et al. Association of Tramadol vs Codeine Prescription Dispensation With Mortality and Other Adverse Clinical Outcomes. JAMA. 2021;326(15):1504-1515.
McCance-Katz EF, et al. Drug Interactions of Clinical Importance among the Opioids, Methadone and Buprenorphine, and other Frequently Prescribed Medications: A Review. Am J Addict. 2010;19(1):4-16.
Hall AK, Cicali EJ, Schentrup D, et al. Phenoconversion and rural pain inequities: a precision-informed roadmap to advance equity for rural older adults. Front Pain Res. 2026;7:1883083.
