Two medicines, side by side
Chlorzoxazone vs tizanidine
Chlorzoxazone and tizanidine are both labeled for muscle spasms and spasticity. Drugs@FDA records approvals of chlorzoxazone since 1958 and of tizanidine since 1996. Pharmacies paid $0.210 per chlorzoxazone 500 mg tablet and $0.0331 per tizanidine HCl 4 mg tablet (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. In FDA's classes, chlorzoxazone is a muscle relaxant and tizanidine a central alpha-2 adrenergic agonist.
Check it at the source: the chlorzoxazone FDA label on DailyMed (effective September 5, 2023); the tizanidine FDA label on DailyMed (effective January 2, 2026).
Highlights of the chlorzoxazone record
Chlorzoxazone (Parafon Forte Dsc) · label of September 5, 2023
Used for
From the label: indicationsChlorzoxazone is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties. Chlorzoxazone does not directly relax tense skeletal muscles in man.
On the market
- Earliest approval on file
- August 15, 1958
- Generic labelers
- 19 labelers
- Pharmacy cost
- $0.210 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 2
Highlights of the tizanidine record
Tizanidine (Zanaflex) · label of January 2, 2026
Used for
From the label: indicationsZanaflex is indicated for the treatment of spasticity in adults. Zanaflex is a central alpha-2-adrenergic agonist indicated for the treatment of spasticity.
On the market
- Earliest approval on file
- November 27, 1996
- Generic labelers
- 49 labelers
- Pharmacy cost
- $0.0331 per tablet
Supply and safety
- Shortage
- No current entry
- Recalls
- 9
Source: FDA drug labels via openFDA (Chlorzoxazone label of September 5, 2023, Tizanidine label of January 2, 2026); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do chlorzoxazone and tizanidine differ on the record?
In FDA's classes, chlorzoxazone is a muscle relaxant and tizanidine a central alpha-2 adrenergic agonist.
Generics: chlorzoxazone since 1981; tizanidine since 2002 (Drugs@FDA).
| Chlorzoxazone | Tizanidine | |
|---|---|---|
| Labeled for | Muscle spasms and spasticity | Muscle spasms and spasticity |
| Pharmacologic class | Muscle Relaxant | Central alpha-2 Adrenergic Agonist |
| How it works (label) | n/a | Tizanidine is a central alpha-2-adrenergic receptor agonist and presumably reduces spasticity by increasing presynaptic inhibition of motor neurons. The effects of tizanidine are greatest on polysynaptic pathways. |
| Half-life (label) | n/a | Elimination Metabolism Tizanidine has a half-life of approximately 2.5 hours (CV=33%). |
| Earliest approval on file (Drugs@FDA) | August 15, 1958 | November 27, 1996 |
| First generic approved | October 6, 1981 | June 27, 2002 |
| Generic labelers (NDC) | 19 labelers | 49 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.210 per tablet (Chlorzoxazone 500 mg tablet) | $0.0331 per tablet (Tizanidine HCl 4 mg tablet) |
| 12-month price change | -5% | -12% |
| Boxed warning | No | No |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 2 | 9 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 1,296 | 41,179 |
| DEA schedule | none | none |
Source: Drugs@FDA, FDA NDC Directory, CMS NADAC of October 7, 2026, FDA shortages and recalls, FAERS via openFDA (FDA files October 8, 2026)
What next?
- Alternatives to chlorzoxazone
- every medicine labeled for the same conditions