What the FDA labels say about taking them together
Propylthiouracil and theophylline
Propylthiouracil's FDA label of August 27, 2026 names theophylline in its drug interactions section; the theophylline label PlainMeds reads does not name propylthiouracil. The propylthiouracil 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 propylthiouracil FDA label on DailyMed (effective August 27, 2026, American Health Packaging); the theophylline FDA label on DailyMed (effective March 10, 2026, Strides Pharma Science Limited).
What does the propylthiouracil label say about theophylline?
Propylthiouracil 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 (Propylthiouracil), American Health Packaging, effective August 27, 2026 (SPL set d819e532-09ac-434a-84a6-636c4204c7aa), via openFDA; the full label on DailyMed
What does the theophylline label say about propylthiouracil?
Theophylline's label (effective March 10, 2026) does not name propylthiouracil 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
| Propylthiouracil | Theophylline | |
|---|---|---|
| Labeled for | n/a | Asthma |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.269 per tablet 50 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