What the FDA labels say about taking them together
Dextromethorphan and fenfluramine
Fenfluramine's FDA label of October 27, 2025 names dextromethorphan in its drug interactions section; the dextromethorphan label PlainMeds reads does not name fenfluramine. The fenfluramine label: “… monoamine oxidase inhibitors [MAOIs], which are contraindicated with FINTEPLA, dextromethorphan, lithium, tramadol, and antipsychotics with serotonergic agonist activity.”
Check it at the source: the dextromethorphan FDA label on DailyMed (effective August 27, 2026); the fenfluramine FDA label on DailyMed (effective October 27, 2025, UCB, Inc.).
What does the dextromethorphan label say about fenfluramine?
Dextromethorphan's label (effective August 27, 2026) does not name fenfluramine 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 fenfluramine label say about dextromethorphan?
Fenfluramine label, drug interactionsConcomitant administration of FINTEPLA and drugs (e.g., SSRIs, SNRIs, TCAs, MAO inhibitors, trazodone, etc.), over-the-counter medications (e.g., dextromethorphan), or herbal supplements (e.g., St. John's Wort) that increase serotonin may increase the risk of serotonin syndrome [see Warnings and Precautions (5.7) ].
Fenfluramine label, warnings and precautionsSerotonin syndrome, a potentially life-threatening condition, may occur with FINTEPLA, particularly with concomitant administration of FINTEPLA with other serotonergic drugs, including, but not limited to, selective serotonin-norepinephrine reuptake inhibitors (SNRIs), selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), bupropion, triptans, dietary supplements (e.g., St. John's Wort, tryptophan), drugs that impair metabolism of serotonin (including monoamine oxidase inhibitors [MAOIs], which are contraindicated with FINTEPLA [see Contraindications (4) ], dextromethorphan, lithium, tramadol, and antipsychotics with serotonergic agonist activity.
Source: FDA drug label (Fintepla), NDA212102 (Ucb Inc), as published by UCB, Inc., effective October 27, 2025 (SPL set e88f360e-33ad-4cd6-b2de-5ef885857c5d), 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 | Fenfluramine | |
|---|---|---|
| Labeled for | Cough and cold | n/a |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.122 per unit 15 mg softgel | n/a |
| 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