What the FDA labels say about taking them together
Osilodrostat and tizanidine
Osilodrostat's FDA label of November 18, 2025 names tizanidine in its drug interactions section; the tizanidine labels PlainMeds reads (3) do not name osilodrostat. The osilodrostat label: “Concomitant use of ISTURISA with strong CYP3A4 and/or CYP2B6 inducers may cause a decrease in osilodrostat concentration and may reduce the efficacy of ISTURISA. …”
Check it at the source: the osilodrostat FDA label on DailyMed (effective November 18, 2025, Recordati Rare Diseases, Inc.); the tizanidine FDA label on DailyMed (effective January 2, 2026, Legacy Pharma USA, Inc.).
What does the osilodrostat label say about tizanidine?
Osilodrostat label, drug interactionsClinical Impact: Concomitant use of ISTURISA with strong CYP3A4 and/or CYP2B6 inducers (…) may cause a decrease in osilodrostat concentration and may reduce the efficacy of ISTURISA. Discontinuation of strong CYP3A4 and/or CYP2B6 inducers while using ISTURISA may cause an increase in osilodrostat concentration and may increase the risk of … coadministered with CYP1A2 and CYP2C19 substrates with a narrow therapeutic index, such as theophylline, tizanidine, and S-mephenytoin [see Clinical Pharmacology (12.3) ].
Source: FDA drug label (Isturisa), Recordati Rare Diseases, Inc., effective November 18, 2025 (SPL set f3a5ec24-63c3-4d83-b1c0-6c550fbe7ae2), via openFDA; the full label on DailyMed
What does the tizanidine label say about osilodrostat?
Tizanidine's label (effective January 2, 2026) and its 2 other brand-application labels do not name osilodrostat in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Zanaflex), Legacy Pharma USA, Inc., effective January 2, 2026 (SPL set 60c27d35-7349-4fc6-86ad-70fffdbe3e08), 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
| Osilodrostat | Tizanidine | |
|---|---|---|
| Labeled for | n/a | Muscle spasms and spasticity |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.0331 per tablet 4 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