What the FDA labels say about taking them together
Fenfluramine and lithium
Fenfluramine's FDA label of October 27, 2025 names lithium in its warnings and precautions section; the lithium labels PlainMeds reads (4) do not name fenfluramine. The fenfluramine label: “… inhibitors [MAOIs], which are contraindicated with FINTEPLA, dextromethorphan, lithium, tramadol, and antipsychotics with serotonergic agonist activity.”
Check it at the source: the fenfluramine FDA label on DailyMed (effective October 27, 2025, UCB, Inc.); the lithium FDA label on DailyMed (effective December 23, 2025, Glenmark Pharmaceuticals Inc., USA).
What does the fenfluramine label say about lithium?
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
What does the lithium label say about fenfluramine?
Lithium's label (effective December 23, 2025) and its 3 other brand-application labels do 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 (Lithium Carbonate), Glenmark Pharmaceuticals Inc., USA, effective December 23, 2025 (SPL set 63b3790f-a9b5-47f4-bae1-ddf8b43c13c1), 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
| Fenfluramine | Lithium | |
|---|---|---|
| Labeled for | n/a | Bipolar disorder |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | n/a | $0.104 per capsule 300 mg capsule |
| 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