Bute (phenylbutazone) is an NSAID, also sold as Bute, Butazolidin, Phenylbute, Equipalazone, Phenylarthrite. Below: how 10 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: Restricted: dose and time limitsFEI: Controlled Medication, detection time 168 h (7 days)HISA/HIWU: detection time 48 h (2 days)named in the rules of 29 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 | 72 h (3 days) plasma / urine | ||
| FEI 2024 (16 December 2024) p. 2 | 4.4 mg/kg/5 days/2x/day · oral | Equipalazone | 2 | 168 h (7 days) |
| FEI 2024 (16 December 2024) p. 2 | 8.8 mg/kg · IV | Phenylarthrite | 6 | 168 h (7 days) |
| FEI 2024 (16 December 2024) p. 2 | 8.8 mg/kg/2x/day 1 + 4.4 mg/kg/2x/day for 10 days · oral | Equipalazone | 6 | 168 h (7 days) |
| HISA / HIWU Last updated on December 8th, 2023 p. 24 | 4.4 mg/kg single IV dose · IV | 17 | 48 h (2 days) plasma | |
| HISA / HIWU 080624 p. 4 | 4.4 mg/kg single IV dose · IV | 17 | 48 h (2 days) plasma | |
| IFHA / EHSLC Undated PDF p. 2 | 4.7mg/kg for 5 days, twice daily · oral | Equipazolone® Arnolds Vet Products Ltd | 2 | 168 h (7 days) urine |
| IFHA / EHSLC Undated PDF p. 2 | 8.8mg/kg, single dose · IV | Phenylarthrite® Vetoquinol SA | 6 | 168 h (7 days) urine |
| IFHA / EHSLC Undated PDF p. 2 | 8.8mg/kg twice daily for 1 day, followed by 4.4mg/kg for 10 days, twice daily · oral | Equipazolone® Intervet SA | 6 | 168 h (7 days) urine |
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 |
|---|---|---|---|
| 4.4 mg/kg single IV dose · IV | 72 h (3 days) | 48 h (2 days) | RMTC advisory p. 5 |
Transcribed from the governing bodies' own documents. Each entry links to the document and quotes the row it came from.
“Phenylbutazone (“bute”) Butazolidin® 2.0 mg/Lb (2.0 grams/1000Lb) >12 hours Oral, IV NSAID” — source p. 10
“CONTROLLED Phenylbutazone Non-steroidal anti-inflammatory” — source p. 30
“PHENYLBUTAZONEC,2, Equipalazone 4.4 mg/kg/5 Oral 2 168 (7d) days/2x/day” — source p. 2
From 2027-01-01: 2027 Equine Prohibited Substances List p. 31 lists it as Controlled Medication.
“The maximum permitted plasma or serum concentration of phenylbutazone is 15.0 micrograms per milliliter.” — source p. 8
“VIO405.1 Phenylbutazone (an NSAID) - The maximum permitted plasma ... concentration of phenylbutazone is 15.0 micrograms per milliliter.” — source p. 45
“1. Phenylbutazone (a NSAID) ... Each 24 hours, not more than 2.0 milligrams per” — source p. 77
“Phenylbutazone ... Permitted ... The maximum permitted plasma concentration of phenylbutazone is 15.0 micrograms per milliliter.” — source
“Bute is administered, the dose should be accurately cal‐ ... Neither a total daily dose nor part of an injectable dose should be administered during the 6 hours prior to competing.” — source p. 7
“Phenylbutazone2,3 ... 4.4 mg/kg single IV dose ... 48 hours (17) ... 0.2 mcg/mL in serum or plasma” — source p. 4
“Phenylbutazone ... 48 hours: 4.4 mg/kg single IV dose. (17 horses) ... 0.2 mcg/mL in serum or plasma. Note: The detection of more” — source p. 24
“Phenylbutazone Butazolidin 4 C*” — source p. 46
“Phenylbutazone | 0.3 micrograms per milliliter of plasma or serum | 48 hours” — source p. 7
“Phenylbutazone Equipazolone® Arnolds Vet Products Ltd 4.7mg/kg for 5 days, twice daily Oral (2) 168 (7 days)” — source p. 2
Bute is named in the medication rules, threshold schedules or withdrawal guidance of 29 state racing commissions: Arizona, California, Colorado, Delaware, Florida, Idaho, Illinois, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Montana, Nebraska, New Jersey, New Mexico, New York, Ohio, Oklahoma, Oregon, Pennsylvania, Texas, Virginia, Washington, West Virginia, Wyoming. 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 Bute 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 Bute as "Restricted Medication Dose and Time Recommendations". Maximum dose: 2.0 mg/Lb (2.0 grams/1000Lb) each 24 hours. Not within 12 h of competition. Screening limit 15.0 micrograms per milliliter in plasma. (Page 10.)
The FEI List of Detection Times gives 168 h (7 days) for 4.4 mg/kg/5 days/2x/day oral (Equipalazone); 168 h (7 days) for 8.8 mg/kg IV (Phenylarthrite); 168 h (7 days) for 8.8 mg/kg/2x/day 1 + 4.4 mg/kg/2x/day for 10 days oral (Equipalazone). On the 2026 FEI Equine Prohibited Substances List Bute 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 Bute is 48 h (2 days) for 4.4 mg/kg single IV dose (17 horses), screening limit 0.2 mcg/mL in serum or plasma. 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 Bute 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.