Cholestyramine and Phenobarbital Interaction
Drug interaction information between Cholestyramine and Phenobarbital.
Cholestyramine and Phenobarbital have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Cholestyramine and Phenobarbital. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Cholestyramine can bind to phenobarbital in your intestines, which reduces how much of the medicine gets into your system. This can make the phenobarbital less effective.
FDA Label Information
Drug Interactions Cholestyramine resin may delay or reduce the absorption of concomitant oral medication such as phenylbutazone, warfarin, thiazide diuretics (acidic) or propranolol (basic), as well as tetracycline, penicillin G, phenobarbital, thyroid and thyroxine preparations, estrogens and progestins and digitalis.
Cholestyramine Also Interacts With
- Naproxen moderate
- Olmesartan moderate
- Raloxifene moderate
- Propranolol minor
- Warfarin minor
Phenobarbital Also Interacts With
- Nirmatrelvir/Ritonavir major
- Ranolazine major
- Voriconazole major
- Canagliflozin moderate
- Cenobamate moderate
Frequently Asked Questions
What SPL severity band is on file for Cholestyramine + Phenobarbital?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Phenobarbital has 59 labeled pairs on file vs Cholestyramine's 34. In the minor band specifically: Cholestyramine has 31 (also Propranolol, Warfarin, Tetracycline, Amiodarone); Phenobarbital has 43 (also Estradiol, Doxycycline, Progesterone, Griseofulvin).
What mechanism field is on file for Cholestyramine and Phenobarbital?
Cholestyramine can bind to phenobarbital in your intestines, which reduces how much of the medicine gets into your system. This can make the phenobarbital less effective.
Phenobarbital carries more major-labeled pairs than Cholestyramine
SPL source-record counts only. This page's band is minor · classes on file: Cholestyramine (Bile Acid Sequestrant); Phenobarbital (Anticonvulsant (Barbiturate)).
Phenobarbital has 3 major-labeled pairs vs Cholestyramine's 0. This page itself is in the minor band, not the major band.
0 major · 3 moderate · 31 minor · 34 total
- Other minor peers for Cholestyramine
- Propranolol
- Warfarin
- Tetracycline
- Amiodarone
3 major · 13 moderate · 43 minor · 59 total
- Other minor peers for Phenobarbital
- Estradiol
- Doxycycline
- Progesterone
- Griseofulvin
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.