What the FDA labels say about taking them together
Dextromethorphan and terbinafine
Terbinafine's FDA label of October 17, 2025 names dextromethorphan in its drug interactions section; the dextromethorphan label PlainMeds reads does not name terbinafine. The terbinafine label: “In studies in healthy subjects characterized as extensive metabolizers of dextromethorphan, terbinafine increases the dextromethorphan/ dextrorphan metabolite ratio in urine by 16- to 97-fold on average.”
Check it at the source: the dextromethorphan FDA label on DailyMed (effective August 27, 2026); the terbinafine FDA label on DailyMed (effective October 17, 2025, PD-Rx Pharmaceuticals, Inc.).
What does the dextromethorphan label say about terbinafine?
Dextromethorphan's label (effective August 27, 2026) does not name terbinafine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Good Sense Cough DM), L. Perrigo Company, effective August 27, 2026 (SPL set 5a2e9bef-42cb-4b72-9a26-c3ae71dcb4ea), via openFDA; the full label on DailyMed
What does the terbinafine label say about dextromethorphan?
Terbinafine label, drug interactionsIn studies in healthy subjects characterized as extensive metabolizers of dextromethorphan (antitussive drug and CYP2D6 probe substrate), terbinafine increases the dextromethorphan/ dextrorphan metabolite ratio in urine by 16- to 97-fold on average.
Source: FDA drug label (Terbinafine Hydrochloride), PD-Rx Pharmaceuticals, Inc., effective October 17, 2025 (SPL set 2df111dc-ecac-4161-9e22-38436eb37c1f), 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
| Dextromethorphan | Terbinafine | |
|---|---|---|
| Labeled for | Cough and cold | Fungal infections |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.122 per unit 15 mg softgel | $0.143 per tablet 250 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