What the FDA labels say about taking them together
Cholestyramine and phenobarbital
Cholestyramine's FDA label of August 20, 2026 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name cholestyramine. The cholestyramine label: “… diuretics (acidic) or propranolol (basic), as well as tetracycline, penicillin G, phenobarbital, thyroid and thyroxine preparations, estrogens and progestins and digitalis.”
Check it at the source: the cholestyramine FDA label on DailyMed (effective August 20, 2026, AiPing Pharmaceutical, Inc.); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the cholestyramine label say about phenobarbital?
Cholestyramine label, drug interactionsDrug 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.
Source: FDA drug label (Cholestyramine), AiPing Pharmaceutical, Inc., effective August 20, 2026 (SPL set 214ea05f-de81-4026-9df9-4ce3820668ee), via openFDA; the full label on DailyMed
What does the phenobarbital label say about cholestyramine?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name cholestyramine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Phenobarbital), Chartwell RX, LLC, effective August 27, 2026 (SPL set 74428144-fb24-40a5-a670-3b876e2d116c), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Cholestyramine | Phenobarbital | |
|---|---|---|
| Labeled for | High cholesterol | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.834 per packet Cholestyramine packet | $0.213 per tablet 100 mg tablet |
| Shortage now | No current entry | A presentation being discontinued |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once