What the FDA labels say about taking them together
Rifampin and theophylline
Theophylline's FDA label of March 10, 2026 names rifampin in its drug interactions section; the rifampin label PlainMeds reads does not name theophylline. The theophylline label: “Drug: Rifampin; Type of Interaction: Increases theophylline clearance by increasing cytochrome P450 1A2 and 3A3 activity.; Effect**: 20 to 40% decrease”
Check it at the source: the rifampin FDA label on DailyMed (effective February 11, 2026, Lupin Pharmaceuticals, Inc.); the theophylline FDA label on DailyMed (effective March 10, 2026, Strides Pharma Science Limited).
What does the rifampin label say about theophylline?
Rifampin's label (effective February 11, 2026) does not name theophylline in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (rifampin), Lupin Pharmaceuticals, Inc., effective February 11, 2026 (SPL set b56004f0-f23d-47f6-80c7-39884fccbccc), via openFDA; the full label on DailyMed
What does the theophylline label say about rifampin?
Theophylline label, drug interactionsDrug: Rifampin; Type of Interaction: Increases theophylline clearance by increasing cytochrome P450 1A2 and 3A3 activity.; Effect**: 20 to 40% decrease
Theophylline label, warningsCessation of Smoking Drug Interactions: Adding a drug that inhibits theophylline metabolism (e.g., cimetidine, erythromycin, tacrine) or stopping a concurrently administered drug that enhances theophylline metabolism (e.g., carbamazepine, rifampin). (See PRECAUTIONS, Drug Interactions, Table II ).
Source: FDA drug label (Theophylline), Strides Pharma Science Limited, effective March 10, 2026 (SPL set b7a90ccf-9c32-40cc-9008-7e55b3da4dfd), 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
| Rifampin | Theophylline | |
|---|---|---|
| Labeled for | n/a | Asthma |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.679 per capsule 300 mg capsule | $0.330 per tablet 300 mg tablet |
| Shortage now | In shortage | No current entry |
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