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Procaine penicillin G withdrawal and detection times for horses

Procaine penicillin G is an antibiotic, also sold as Procaine Penicillin, Procaine Benzylpenicillin, Penicillin G Procaine. Below: how 6 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 conditionsHISA: Controlled medicationnamed in the rules of 19 state racing commissions

Published detection times for Procaine penicillin G

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 documentDose and route studiedFormulationHorsesDetection time
USEF (US Equestrian)
2026 (last revised 1 Dec 2025; amendments effect… p. 11
dose not stated in the row336 h (14 days)
plasma / urine
Equestrian Canada
Rev. January 15, 2025 p. 18
IM · IM425 h
IFHA / EHSLC
Undated PDF p. 2
12mg/kg for 5 days, once or twice daily · IMDepocillin® MSD Animal Healt4240 h (10 days)
plasma

How each rulebook lists Procaine penicillin G

Transcribed from the governing bodies' own documents. Each entry links to the document and quotes the row it came from.

USEF (US Equestrian)

2026 USEF Guidelines & Rules for Drugs and Medications (with 27 Jul 2026 Guidelines Update) p. 9 · 2026 (last revised 1 Dec 2025; amendments effective 27 Jul 2026, published 10 Aug 2026)
Permitted with conditions
  • Listed as: Potentially Permitted with Medication Report Form (MRF) according to GR411 · Timing: not within 24 h (1 day) of competition · Routes: IM · Medication report form: required
  • Listed as: How Long Drugs Remain Detectable · Detection time: 336 h (14 days) for the dose studied · Medication report form: required
“Potentially Permitted with Medication Report Form (MRF) according to GR411: ... procaine penicillin (penicillin G; intramuscular)” — source p. 9

Equestrian Canada

Controlled medication
  • Listed as: Prohibited substance
  • Listed as: Prohibited substance · Detection time: 425 h for IM · Routes: IM
“Penicillin G Procaine” — source p. 11

NCHA

2026 NCHA Rule Book - Standing Rule 35A, Medication and Drug Rules and Guidelines p. 5 · 2026 Rule Book, SR 35A extract (pages 75-95; PDF created 30 Jun 2026)
Permitted with conditions
  • Listed as: Conditionally permitted (35A.8.b.iii) · Timing: not within 24 h (1 day) of competition · Medication report form: required
“Procaine penicillin or other anti‐ biotic with local anesthetics are prohibited substances.” — source p. 5

HISA / HIWU

HISA Prohibited List (Rule Series 4000), Anti-Doping and Medication Control Program p. 3 · Rule 4000 Series as published in the Federal Register 88 FR 5070 (Jan 26 2023, doc 2023-00957); FTC-approved Mar 27 2023; in force May 22 2023; current posted version on hisaus.org/regulations
Controlled medication
  • Listed as: S7 Controlled Medication Substances
“excluding procaine penicillin or other antimicrobial/anti-infective agents containing or metabolizing to Prohibited Substances” — source p. 3

ARCI

ARCI Controlled Therapeutic Medication Schedule for Horses p. 5 · Version 4.2.1 (Revised December 2020); policies from Model Rules Version 15 (August 2026)
Permitted up to a threshold
  • Listed as: Controlled Therapeutic Medication · Dose in the rule: Intramuscular · Screening limit: 25 nanograms per milliliter of plasma or serum · Routes: IM · Medication report form: required
“Procaine penicillin (administration must be reported to Commission) | 25 nanograms per milliliter of plasma or serum | Following entry to race” — source p. 5

IFHA / EHSLC

Controlled medication
  • Listed as: Legitimate therapeutic substance controlled by International Screening Limit · Screening limit: 0.02 ng/mL (plasma ISL of procaine) · Detection time: 240 h (10 days) for 12mg/kg for 5 days, once or twice daily · Routes: IM
“Procaine benzylpenicillin Depocillin® MSD Animal Healt 12mg/kg for 5 days, once or twice daily i.m. (4) 240 &” — source p. 2

State racing commissions

Procaine penicillin G is named in the medication rules, threshold schedules or withdrawal guidance of 19 state racing commissions: Arizona, California, Colorado, Florida, Illinois, Indiana, Kentucky, Louisiana, Maine, Maryland, 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.

Detection time is not withdrawal time

A published detection time tells you how long Procaine penicillin G 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.

A detection time is the approximate period a drug or its metabolite stayed detectable in the horses studied, at the dose and route studied. It is not a withdrawal time. No governing body publishes withdrawal times for you; your veterinarian sets the safety margin for your horse. Nothing on this page is a veterinary ruling or a promise that a horse will test clean. Rules change; the document, version and page behind every value are linked so you can check the current text.

Questions about Procaine penicillin G

Is Procaine penicillin G allowed at USEF shows?

The 2026 USEF Guidelines & Rules for Drugs and Medications (with 27 Jul 2026 Guidelines Update) list Procaine penicillin G as "Potentially Permitted with Medication Report Form (MRF) according to GR411". Not within 24 h (1 day) of competition. (Page 9.)

Does a published detection time mean my horse will test clean?

No. It is the approximate time Procaine penicillin G 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.

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