Diclofenac Transdermal Patch and Cholestyramine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Cholestyramine
Diclofenac Transdermal Patch
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.
What happens
Decreased diclofenac bioavailability
Interaction Deep Dive
Single doses of colestipol 10 g, cholestyramine 8 g, or placebo were administered following a dose of diclofenac 100 mg to healthy volunteers in a randomized, crossover study that consisted of three phases. Results showed that the area under the concentration-time curve (AUC) of diclofenac was decreased by 33% and 62% in the presence of colestipol and cholestyramine, respectively. Maximum concentration (Cmax) was also reduced by colestipol (58%) and cholestyramine (75%)1.
Why it happens (mechanism)
Decreased diclofenac absorption in the gastrointestinal tract
Literature reports
1 report — tap to read
a) Six healthy male volunteers participated in a randomized crossover study which consisted of three phases to determine the effect of the bile resins colestipol and cholestyramine on the pharmacokinetics of diclofenac. Each subject ingested a single dose of diclofenac 100 mg on three occasions, followed by either cholestyramine 8 g, colestipol 10 g, or water. These doses of colestipol and cholestyramine were chosen because they are standard doses used in the treatment of hypercholesterolemia. Cholestyramine decreased the mean area under the concentration-time curve (AUC) of diclofenac by 62% (4196.5 ng/h/mL vs. 1605.2 ng/h/mL). Maximum concentration (Cmax) of diclofenac was also decreased from 3355.3 ng/mL to 838.5 ng/mL, representing a 75% reduction. Because approximately 30% to 35% of a diclofenac dose undergoes enterohepatic cycling, separating the times of administration of diclofenac and cholestyramine may not completely eliminate the possibility of this interaction 1.
Common questions
Can I take Diclofenac Transdermal Patch and Cholestyramine together?
Decreased diclofenac bioavailability Always confirm with your pharmacist or prescriber before making any change.
How serious is the Diclofenac Transdermal Patch and Cholestyramine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Diclofenac Transdermal Patch or Cholestyramine 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 anything you'd monitor while I'm on both?
References (1)
- Al-Balla SR, El-Sayed YM, Al-Meshal MA, et al: The effects of cholestyramine and colestipol on the absorption of diclofenac in man. Int J Clin Pharmacol Ther 1994; 32:441-445.
Keep reading about Cholestyramine
Keep reading about Diclofenac Transdermal Patch
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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