What the FDA labels say about taking them together
Primaquine and theophylline
Primaquine's FDA label of February 11, 2026 names theophylline in its drug interactions section; the theophylline label PlainMeds reads does not name primaquine. The primaquine label: “Effects of Primaquine on the Pharmacokinetics of Other Drugs CYP1A2 Substrates Published clinical and non-clinical reports indicate primaquine inhibits CYP1A2 enzyme activity and thus may lead to increased exposure of …”
Check it at the source: the primaquine FDA label on DailyMed (effective February 11, 2026, Sanofi-Aventis U.S. LLC); the theophylline FDA label on DailyMed (effective March 10, 2026, Strides Pharma Science Limited).
What does the primaquine label say about theophylline?
Primaquine label, drug interactionsEffects of Primaquine on the Pharmacokinetics of Other Drugs CYP1A2 Substrates Published clinical and non-clinical reports indicate primaquine inhibits CYP1A2 enzyme activity and thus may lead to increased exposure of CYP1A2 substrate drugs (e.g., duloxetine, alosetron, theophylline and tizanidine) when co-administered with Primaquine phosphate Tablets.
Source: FDA drug label (Primaquine Phosphate), Sanofi-Aventis U.S. LLC, effective February 11, 2026 (SPL set 1bfbf4ae-81b8-4160-a00d-6322aadd4b59), via openFDA; the full label on DailyMed
What does the theophylline label say about primaquine?
Theophylline's label (effective March 10, 2026) does not name primaquine 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
| Primaquine | Theophylline | |
|---|---|---|
| Labeled for | n/a | Asthma |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $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