Lasix (furosemide) is a diuretic, also sold as Lasix, Salix, Frusemide. 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: Permitted with conditionsFEI: Controlled MedicationHISA: Controlled medicationnamed in the rules of 31 state racing commissions
None of the detection-time lists we carry (FEI, HIWU, IFHA/EHSLC, Equestrian Canada, USEF) publishes a detection time for Lasix. ShowSafe Pro answers "Unknown" for it, never "Clear", and quotes what each rulebook says about unlisted substances.
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 |
|---|---|---|---|
| 1 mg/kg IV single IV dose (where permitted by exemption) · IV | 4 h | 4 h | RMTC advisory p. 3 |
| 48 h (2 days) | 48 h (2 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: ... furosemide (Lasix®)” — source p. 9
“CONTROLLED Furosemide Diuretic” — source p. 18
From 2027-01-01: 2027 Equine Prohibited Substances List p. 19 lists it as Controlled Medication.
“Furosemide” — source p. 11
“VIO405.9 Furosemide (Lasix®) – The maximum plasma concentration of ... furosemide must be administered intravenously at least four hours prior to competition.” — source p. 47
“10. Furosemide or Lasix, when used, must be administered intravenously at least four (4) hours prior to competition.” — source p. 79
“Furosemide ... Permitted ... The maximum permitted plasma concentration of furosemide is 10 nanograms per milliliter.” — source
“k. Furosemide ... Must be adminis‐ tered intravenously at least four hours prior to competi‐” — source p. 11
“Furosemide ... RAT: 48 hours (6) ... 50 ng/mL in urine or 0.1 ng/mL in serum or plasma” — source p. 3
“*Furosemide ... Restricted Administration: 48 hours. 1 mg/kg single IV dose (6 horses) ... 50 ng/mL in urine or 0.1 ng/mL in serum or plasma” — source p. 13
“(4) furosemide (also known as Lasix/ Salix), subject to the limitations set out in Rule 4212(d).” — source p. 2
“Furosemide Lasix N/A” — source p. 31
“Furosemide | 100 nanogram per milliliter of plasma or serum | 4 hours” — source p. 3
“Furosemide Dimazon® Intervet 1mg/kg, single dose i.v. (6) ≤48 ^” — source p. 1
Lasix is named in the medication rules, threshold schedules or withdrawal guidance of 31 state racing commissions: Arizona, California, Colorado, Delaware, Florida, Idaho, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Montana, Nebraska, New Jersey, New Mexico, New York, North Dakota, 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 Lasix 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 Lasix 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 Lasix is a Controlled Medication. The FEI states that a detection time is not a withdrawal time; the treating veterinarian adds a safety margin.
No. It is the approximate time Lasix 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.