Fentanyl and Cyclobenzaprine Interaction
Drug interaction information between Fentanyl and Cyclobenzaprine.
Fentanyl and Cyclobenzaprine have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Fentanyl and Cyclobenzaprine. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Both drugs increase the level of a brain chemical called serotonin. Taking them together can cause too much serotonin to build up in your body, which can be dangerous.
What To Do
Your doctor should monitor you closely for signs of serotonin syndrome, such as confusion, a fast heartbeat, or muscle stiffness.
FDA Label Information
Examples: Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that effect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue).
Fentanyl Also Interacts With
- Itraconazole moderate
- Tranylcypromine moderate
- Tramadol minor
- Ketoconazole minor
- Diazepam minor
Cyclobenzaprine Also Interacts With
- Clozapine moderate
- Tapentadol moderate
- Tranylcypromine moderate
- Acetaminophen/Oxycodone minor
- Buprenorphine minor
Frequently Asked Questions
Can I take Fentanyl and Cyclobenzaprine together?
This is a minor interaction. Your doctor should monitor you closely for signs of serotonin syndrome, such as confusion, a fast heartbeat, or muscle stiffness.
How serious is the interaction between Fentanyl and Cyclobenzaprine?
This interaction is classified as "minor" severity by the FDA. Minor interactions are unlikely to cause significant problems but should still be mentioned to your healthcare provider.
Why do Fentanyl and Cyclobenzaprine interact?
Both drugs increase the level of a brain chemical called serotonin. Taking them together can cause too much serotonin to build up in your body, which can be dangerous.
Understanding the Fentanyl and Cyclobenzaprine Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Fentanyl belongs to the Opioid Analgesic class and Cyclobenzaprine belongs to the Muscle Relaxant class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Both drugs increase the level of a brain chemical called serotonin. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Fentanyl has 28 total documented interactions on file in this dataset, and Cyclobenzaprine has 17. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Your doctor should monitor you closely for signs of serotonin syndrome, such as confusion, a fast heartbeat, or muscle stiffness. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Fentanyl or Cyclobenzaprine based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.