Predef 2X (isoflupredone) is a corticosteroid, also sold as Isoflupredone Acetate, Predef 2X, Predef. 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 336 h (14 days)named in the rules of 17 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 |
|---|---|---|---|---|
| USEF (US Equestrian) 2026 (last revised 1 Dec 2025; amendments effect… p. 11 | dose not stated in the row · other | 672 h (28 days) plasma / urine | ||
| USEF (US Equestrian) 2026 (last revised 1 Dec 2025; amendments effect… p. 11 | dose not stated in the row · intra-articular | 168 h (7 days) plasma / urine | ||
| HISA / HIWU Last updated on December 8th, 2023 p. 16 | experimental dose of 8 mg IA single joint · intra-articular | 6 | 336 h (14 days) plasma | |
| HISA / HIWU 080624 p. 4 | experimental dose of 8 mg IA single joint · intra-articular | 6 | 336 h (14 days) plasma |
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: ... isoflupredone (Predef 2x®)” — source p. 9
“CONTROLLED Isoflupredone Corticosteroid” — source p. 20
From 2027-01-01: 2027 Equine Prohibited Substances List p. 21 lists it as Controlled Medication.
“Isoflupredone” — source p. 11
“Isoflupredone ... Conditionally Permitted ... Conditionally permitted substances require a 24-hour withdrawal prior to the horse competing.” — source
“3. Isoflupredone – 50 mg.” — source p. 14
“Isoflupredone4 ... Serum concentrations associated with an experimental dose of 8 mg IA single joint (6 horses) were all below Limit of Detection by 14 days” — source p. 4
“Isoflupredone ... 14 day stand down for all intra-articular injections.” — source p. 16
“Isoflupredone Predef 2x 4 C” — source p. 34
“Isoflupredone Harness Racing Only. | 100 picograms per milliliter of plasma or serum SEE NOTE BELOW | 7 days” — source p. 4
Predef 2X is named in the medication rules, threshold schedules or withdrawal guidance of 17 state racing commissions: Arizona, Colorado, Florida, Illinois, Indiana, Kentucky, Louisiana, Maine, Minnesota, Nebraska, New York, Ohio, Oklahoma, Oregon, Pennsylvania, 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 Predef 2X 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 Predef 2X 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 Predef 2X 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 Predef 2X is 336 h (14 days) for experimental dose of 8 mg IA single joint (6 horses). A detection time is not a withdrawal time; HISA leaves the safety margin to your veterinarian.
No. It is the approximate time Predef 2X 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.