Fever Bark - Cymbalta (Duloxetine) Interaction
Herbal: Fever Bark
Also Known As: Alstonia constricta, Alstonia Bark, Australian Febrifuge, Australian Fever Bush, Australian Quinine, Bitterbark, Corteza de Alstonia, Devil Tree, Devil's Bit, Dita Bark, Écorce Amère d'Australie, Écorce de Quinquina, Écorce de Quinquina d'Australie
Drug: Duloxetine
Brand names:
Cymbalta, Drizalma Sprinkle, Irenka

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Jun 22, 2025
Interaction Details
Duloxetine is classified as belonging to the following category: Cytochrome P450 2D6 (Cyp2D6) Substrates
Theoretically, fever bark might increase the levels and clinical effects of CYP2D6 substrates.
In vitro research suggests that yohimbine, a constituent of fever bark, inhibits CYP2D6 enzyme activity. The effects of fever bark itself are unclear.
Interaction Rating
Likelihood of Occurrence
PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
References
- VandenBrink, B. M., Foti, R. S., Rock, D. A., Wienkers, L. C., and Wahlstrom, J. L. Prediction of CYP2D6 drug interactions from in vitro data: evidence for substrate-dependent inhibition. Drug Metab Dispos. 2012;40(1):47-53.
Interaction Details
Duloxetine is classified as belonging to the following category: Cytochrome P450 2D6 (Cyp2D6) Inhibitors
Theoretically, CYP2D6 inhibitors might increase the levels and clinical effects of yohimbine, a constituent of fever bark.
In vitro and clinical research shows that the fever bark constituent, yohimbine, is metabolized by CYP2D6 isoenzymes.
Interaction Rating
Likelihood of Occurrence
PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
References
- Le Corre P, Parmer RJ, Kailasam MT, et al. Human sympathetic activation by alpha2-adrenergic blockade with yohimbine: Bimodal, epistatic influence of cytochrome P450-mediated drug metabolism. Clin Pharmacol Ther. 2004;76(2):139-53.
- Mueller-Schoell A, Michelet R, Weinelt F, Kloft C, Mikus G. CYP2D6 phenotype explains reported yohimbine concentrations in four severe acute intoxications. Arch Toxicol. 2021.
- Bharucha AE, Skaar T, Andrews CN, et al Relationship of cytochrome P450 pharmacogenetics to the effects of yohimbine on gastrointestinal transit and catecholamines in healthy subjects. Neurogastroenterol Motil. 2008;20(8):891-9.
Fever Bark Overview

Duloxetine Overview
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Duloxetine is used to treat depression in adults and generalized anxiety disorder (GAD; excessive worry and tension that disrupts daily life and lasts for 6 months or longer) in adults and children 7 years of age and older. Duloxetine is also used to treat pain and tingling caused by diabetic neuropathy (damage to nerves that can develop in people who have diabetes) in adults and fibromyalgia (a long-lasting condition that may cause pain, muscle stiffness and tenderness, tiredness, and difficulty falling asleep or staying asleep) in adults and children 13 years of age and older. It is also used to treat ongoing bone or muscle pain such as lower back pain or osteoarthritis (joint pain or stiffness that may worsen over time) in adults. Duloxetine is in a class of medications called selective serotonin and norepinephrine reuptake inhibitors (SNRIs). It works by increasing the amounts of serotonin and norepinephrine, natural substances in the brain that help maintain mental balance and stop the movement of pain signals in the brain.
Fever Bark - More Interactions
Fever Bark interacts with 790 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
Unknown | No interactions have been reported or no interaction data is currently available. |
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Parts of this content are provided by the Therapeutic Research Center, LLC.
DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.
© 2021 Therapeutic Research Center, LLC
Drug descriptions are provided by MedlinePlus.