What the FDA labels say about taking them together
Methimazole and theophylline
Methimazole's FDA label of August 20, 2026 names theophylline in its drug interactions section; the theophylline label PlainMeds reads does not name methimazole. The methimazole label: “Theophylline: Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.”
Check it at the source: the methimazole FDA label on DailyMed (effective August 20, 2026, AiPing Pharmaceutical, Inc.); the theophylline FDA label on DailyMed (effective March 10, 2026, Strides Pharma Science Limited).
What does the methimazole label say about theophylline?
Methimazole label, drug interactionsTheophylline: Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.
Source: FDA drug label (Methimazole), AiPing Pharmaceutical, Inc., effective August 20, 2026 (SPL set 06bb4bcc-5e47-48b6-a76c-648f846704e8), via openFDA; the full label on DailyMed
What does the theophylline label say about methimazole?
Theophylline's label (effective March 10, 2026) does not name methimazole in these sections. A label lists what its studies and reports found; it is not a complete list.
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
| Methimazole | Theophylline | |
|---|---|---|
| Labeled for | n/a | Asthma |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0702 per tablet 5 mg tablet | $0.330 per tablet 300 mg tablet |
| Shortage now | No current entry | 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