Two medicines, side by side
Dantrolene vs tizanidine
Dantrolene and tizanidine are both labeled for muscle spasms and spasticity. Drugs@FDA records approvals of dantrolene since 1974 and of tizanidine since 1996. Pharmacies paid $0.409 per dantrolene sodium 25 mg capsule 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, dantrolene is a skeletal muscle relaxant and tizanidine a central alpha-2 adrenergic agonist.
Check it at the source: the dantrolene FDA label on DailyMed (effective August 21, 2026); the tizanidine FDA label on DailyMed (effective January 2, 2026).
Highlights of the dantrolene record
Dantrolene (Ryanodex) · label of August 21, 2026
Dantrolene sodium has a potential for hepatotoxicity, and should not be used in conditions other than those recommended. Symptomatic hepatitis (fatal and non-fatal) has been reported at various dose levels of the drug. The incidence reported in patients taking up to 400 mg/day is much lower than in those taking doses of 800 mg or more per day. Even sporadic short courses of these higher dose levels within a treatment regimen markedly increased the risk of serious hepatic injury.
Used for
From the label: indicationsIn Chronic Spasticity: Dantrolene sodium is indicated in controlling the manifestations of clinical spasticity resulting from upper motor neuron disorders (e.g., spinal cord injury, stroke, cerebral palsy, or multiple sclerosis). It is of particular benefit to the patient whose functional rehabilitation has been retarded by the sequelae of spasticity. […]
On the market
- Earliest approval on file
- January 15, 1974
- Generic labelers
- 10 labelers
- Pharmacy cost
- $0.409 per capsule
Supply and safety
- Shortage
- No current entry
- Recalls
- 3
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 (Dantrolene label of August 21, 2026, Tizanidine label of January 2, 2026); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do dantrolene and tizanidine differ on the record?
In FDA's classes, dantrolene is a skeletal muscle relaxant and tizanidine a central alpha-2 adrenergic agonist.
Half-life, in each label's words: Dantrolene, “The mean biologic half-life of dantrolene sodium in adults is 8.7 hours after a 100-mg dose.”; Tizanidine, “Elimination Metabolism Tizanidine has a half-life of approximately 2.5 hours (CV=33%).”
Only the dantrolene label carries a boxed warning.
Generics: dantrolene since 2005; tizanidine since 2002 (Drugs@FDA).
| Dantrolene | Tizanidine | |
|---|---|---|
| Labeled for | Muscle spasms and spasticity | Muscle spasms and spasticity |
| Pharmacologic class | Skeletal 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) | The mean biologic half-life of dantrolene sodium in adults is 8.7 hours after a 100-mg dose. | Elimination Metabolism Tizanidine has a half-life of approximately 2.5 hours (CV=33%). |
| Earliest approval on file (Drugs@FDA) | January 15, 1974 | November 27, 1996 |
| First generic approved | March 1, 2005 | June 27, 2002 |
| Generic labelers (NDC) | 10 labelers | 49 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.409 per capsule (Dantrolene sodium 25 mg capsule) | $0.0331 per tablet (Tizanidine HCl 4 mg tablet) |
| 12-month price change | +3% | -12% |
| Boxed warning | Yes | No |
| Shortage now | No current entry | No current entry |
| Recalls recorded | 3 | 9 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 1,745 | 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 dantrolene
- every medicine labeled for the same conditions