What the FDA labels say about taking them together
Tizanidine and vemurafenib
Vemurafenib's FDA label of August 28, 2026 names tizanidine in its drug interactions section; the tizanidine labels PlainMeds reads (3) do not name vemurafenib. The vemurafenib label: “Vemurafenib on CYP1A2 Substrates Coadministration of ZELBORAF with tizanidine, a sensitive CYP1A2 substrate, increased tizanidine systemic exposure by 4.7-fold.”
Check it at the source: the tizanidine FDA label on DailyMed (effective January 2, 2026, Legacy Pharma USA, Inc.); the vemurafenib FDA label on DailyMed (effective August 28, 2026, Genentech, Inc.).
What does the tizanidine label say about vemurafenib?
Tizanidine's label (effective January 2, 2026) and its 2 other brand-application labels do not name vemurafenib 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
What does the vemurafenib label say about tizanidine?
Vemurafenib label, drug interactionsVemurafenib on CYP1A2 Substrates Coadministration of ZELBORAF with tizanidine, a sensitive CYP1A2 substrate, increased tizanidine systemic exposure by 4.7-fold.
Source: FDA drug label (ZELBORAF), NDA202429 (Hoffmann La Roche), as published by Genentech, Inc., effective August 28, 2026 (SPL set 38eea320-7e0c-485a-bc30-98c3c45e2763), 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
| Tizanidine | Vemurafenib | |
|---|---|---|
| Labeled for | Muscle spasms and spasticity | n/a |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0331 per tablet 4 mg tablet | 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