Dantrium (dantrolene) is a muscle relaxant, also sold as Dantrium. Below: how 7 show and racing governing bodies list it, every published detection time for the dose and route studied, and the document and page each value comes from.USEF: Permitted with conditionsFEI: Controlled MedicationHISA/HIWU: detection time 48 h (2 days)named in the rules of 20 state racing commissions
Each row is one study the governing body published: its own dose, route and formulation. A different dose or route was not studied, and the body says so.
| Body and document | Dose and route studied | Formulation | Horses | Detection time |
|---|---|---|---|---|
| HISA / HIWU Last updated on December 8th, 2023 p. 8 | 500 mg orally once daily for 3 days · oral | 12 | 48 h (2 days) plasma / urine | |
| HISA / HIWU 080624 p. 3 | 500 mg orally once daily for 3 days · oral | 12 | 48 h (2 days) plasma / urine | |
| RMTC (advisory) Updated September 30, 2024 p. 3 | 500 mg orally once daily for 3 days · oral | FDA-approved capsules | 12 | 48 h (2 days) |
The Racing Medication and Testing Consortium publishes withdrawal guidance built on HISA's detection times. It is advisory, not a rule, and ShowSafe Pro shows it beside the HISA result, never in place of it.
| Dose and route | Withdrawal guidance | HISA detection time | Source |
|---|---|---|---|
| 500 mg orally once daily for 3 days · oral | 72 h (3 days) | RMTC advisory p. 3 |
Transcribed from the governing bodies' own documents. Each entry links to the document and quotes the row it came from.
“Potentially Permitted with Medication Report Form (MRF) according to GR411: ... dantrolene (Dantrium®)” — source p. 9
“CONTROLLED Dantrolene Muscle relaxant” — source p. 11
From 2027-01-01: 2027 Equine Prohibited Substances List p. 11 lists it as Controlled Medication.
“Dantrolene ... Conditionally Permitted ... Conditionally permitted substances require a 24-hour withdrawal prior to the horse competing.” — source
“i. Dantrolene ... not exceed 500 milligrams total and is typically adminis‐” — source p. 11
“Dantrolene ... 500 mg orally once daily for 3 days ... 48 hours (12) ... 3 ng/mL of 5-hydroxydantrolene in unhydrolyzed urine or 0.1 ng/mL in serum or plasma as 3-hydroxydantrolene” — source p. 3
“Dantrolene ... 48 hours: 500 mg orally once daily for 3 days (12 horses) ... 3 ng/mL of 5-hydroxy- dantrolene in urine; 0.1 ng/mL in” — source p. 8
“Dantrolene Dantrium 4 C” — source p. 23
“Dantrolene | 100 picograms per milliliter of 5-hydroxydantrolene in plasma or serum | 48 hours” — source p. 2
“Dantrolene Dantrium® 500mg for 3 days, once daily Oral (12) ≤48” — source p. 1
Dantrium is named in the medication rules, threshold schedules or withdrawal guidance of 20 state racing commissions: Arizona, California, Colorado, Florida, Illinois, Indiana, Kentucky, Louisiana, Maine, Maryland, Minnesota, Nebraska, New York, Ohio, Oklahoma, Oregon, Pennsylvania, Texas, Washington, West Virginia. Most states publish thresholds (concentrations), not times, and several adopt the ARCI schedule by reference. ShowSafe Pro Racing layers each state's rules over HISA or ARCI the way that state applies them, for all 32 states with live pari-mutuel racing.
A published detection time tells you how long Dantrium stayed detectable in a handful of horses given one dose by one route. It does not tell you when your horse is clear: a bigger dose, a different route, repeated doses, a joint injection or a slower horse all push the real figure out, and every governing body says to add a safety margin set by your veterinarian. Here is how to read the rulebook.
ShowSafe Pro takes the doses already logged for your horse, matches each one to the published row for that dose and route, adds the margin your vet set, and flags anything the studies never covered as Unknown, ask your vet instead of guessing. Every answer shows the document, page and line it came from, for every rulebook the show runs under.
The 2026 USEF Guidelines & Rules for Drugs and Medications (with 27 Jul 2026 Guidelines Update) list Dantrium as "Potentially Permitted with Medication Report Form (MRF) according to GR411". Not within 24 h (1 day) of competition. (Page 9.)
On the 2026 FEI Equine Prohibited Substances List Dantrium is a Controlled Medication. The FEI states that a detection time is not a withdrawal time; the treating veterinarian adds a safety margin.
HIWU's published detection time for Dantrium is 48 h (2 days) for 500 mg orally once daily for 3 days (12 horses), screening limit 3 ng/mL of 5-hydroxy-dantrolene in urine; 0.1 ng/mL in serum or plasma as 3'-hydroxy-dantrolene. RMTC's advisory withdrawal guidance for the same dose is 72 h (3 days). A detection time is not a withdrawal time; HISA leaves the safety margin to your veterinarian.
No. It is the approximate time Dantrium stayed detectable in the horses studied, at that dose and route. Your horse, dose, route and number of doses may differ. Every governing body tells you to add a safety margin set by your veterinarian, and none publishes a withdrawal time. ShowSafe Pro applies the published row for the dose and route you actually gave, adds your vet's margin, and says 'Unknown' when the studies do not cover what you gave.