What the FDA labels say about taking them together
Amitriptyline and levothyroxine
Levothyroxine's FDA label of February 20, 2024 names amitriptyline in its drug interactions section; the amitriptyline label PlainMeds reads does not name levothyroxine. The levothyroxine label: “Drug or Drug Class: Antidepressants - Tricyclics (e.g., Amitriptyline) - Tetracyclics (e.g., Maprotiline) - Selective Serotonin Reuptake Inhibitors (SSRIs; e.g., Sertraline); …”
Check it at the source: the amitriptyline FDA label on DailyMed (effective September 8, 2026, Sun Pharmaceutical Industries, Inc.); the levothyroxine FDA label on DailyMed (effective February 20, 2024, AbbVie Inc.).
What does the amitriptyline label say about levothyroxine?
Amitriptyline's label (effective September 8, 2026) does not name levothyroxine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Amitriptyline Hydrochloride), Sun Pharmaceutical Industries, Inc., effective September 8, 2026 (SPL set 4e520c63-1cf6-40f6-a51c-3f9b0e181342), via openFDA; the full label on DailyMed
What does the levothyroxine label say about amitriptyline?
Levothyroxine label, drug interactionsConcurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and SYNTHROID may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines.
Levothyroxine Sodium label (Amneal Pharmaceuticals NY LLC, December 6, 2024), drug interactionsDrug or Drug Class: Antidepressants - Tricyclics (e.g., Amitriptyline) - Tetracyclics (e.g., Maprotiline) - Selective Serotonin Reuptake Inhibitors (SSRIs; e.g., Sertraline); Effect: Concurrent use of tri/tetracyclic antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines.Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements.
Source: FDA drug label (Levothyroxine Sodium, NDA021210), Amneal Pharmaceuticals NY LLC, effective December 6, 2024 (SPL set fca88c97-5cd4-4834-ba87-deb5bd637788), via openFDA
Source: FDA drug label (Levothyroxine Sodium, NDA021116), Bryant Ranch Prepack, effective July 29, 2025 (SPL set 9e3bffb9-f66e-4c73-befc-e60d769f6610), via openFDA
Source: FDA drug label (Levoxyl, NDA021301), Pfizer Laboratories Div Pfizer Inc, effective December 15, 2020 (SPL set 758588c3-c63e-491b-0aa2-4f50d80cb174), via openFDA
Source: FDA drug label (Synthroid), AbbVie Inc., effective February 20, 2024 (SPL set 1e11ad30-1041-4520-10b0-8f9d30d30fcc), 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
| Amitriptyline | Levothyroxine | |
|---|---|---|
| Labeled for | Depression | Hypothyroidism |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.03 per tablet 10 mg tablet | $0.0588 per tablet 112 mcg 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