The Science of Trusted




Trust the original altrenogest solution for horses.

  • Trust genuine REGU-MATE® (altrenogest) Solution 0.22% for proven palatability, bioavailability and efficacy in every dose
  • The only FDA-approved altrenogest with more than 50 million doses sold
  • Delivers safe, predictable control over a mare’s reproductive cycle and reduces undesirable mood and behavioral changes
  • 15-day treatment regimen lets performance mares compete at their best
  • Strategic use helps accommodate mare’s performance schedule
  • Easy-to-administer with REGU-MATE® dosing device

Talk to your veterinarian about proper use and safe handling of REGU-MATE® (altrenogest) Solution 0.22%. Avoid skin contact. Always wear protective gloves when administering REGU-MATE® (altrenogest) Solution 0.22%. REGU-MATE® (altrenogest) Solution 0.22% is contraindicated for use in mares having a previous or current history of uterine inflammation. When treatment is discontinued, mares exhibiting regular estrous cycles return to estrus within 4 to 5 days following treatment and continue to cycle normally. Pregnant women or women who suspect they are pregnant should not handle REGU-MATE® (altrenogest) Solution 0.22%.


REGU-MATE (altrenogest) Solution 0.22% is indicated to suppress estrus in mares. Suppression of estrus allows for a predictable occurrence of estrus following drug withdrawal. This facilitates the attainment of regular cyclicity during the transition from winter anestrus to the physiological breeding season. Suppression of estrus will also facilitate management of prolonged estrus conditions. Suppression of estrus may be used to facilitate scheduled breeding during the physiological breeding season.



While wearing protective gloves, remove shipping cap and seal; replace with enclosed plastic dispensing cap. Remove cover from bottle dispensing tip and connect luer lock syringe (without needle). Draw out appropriate volume of REGU-MATE solution. (Note: Do not remove syringe while bottle is inverted as spillage may result.) Detach syringe and administer solution orally at the rate of 1 mL per 110 pounds body weight (0.044 mg/kg) once daily for 15 consecutive days. Administer solution directly on the base of the mare’s tongue or on the mare’s usual grain ration. Replace cover on bottle dispensing tip to prevent leakage. Excessive use of a syringe may cause the syringe to stick; therefore, replace syringe as necessary.


REGU-MATE (altrenogest) Solution 0.22% is contraindicated for use in mares having a previous or current history of uterine inflammation (i.e., acute, subacute, or chronic endometritis). Natural or synthetic gestagen therapy may exacerbate existing low-grade or ‘smoldering’ uterine inflammation into a fulminating uterine infection in some instances.


Various synthetic progestins, including altrenogest, when administered to rats during the embryogenic stage of pregnancy at doses manyfold greater than the recommended equine dose caused fetal anomalies, specifically masculinization of the female genitalia.


REGU-MATE (altrenogest) Solution 0.22% is readily absorbed by the skin. Skin contact must be avoided; protective gloves must be worn when handling this product.


Keep your clinic up-to-date on the Merck Animal Health line of equine products.

The Science of Trusted

The Science of Trusted

Learn more about REGU-MATE, the original altrenogest solution for horses.


Better Mare Management: How to Manage Broodmares and Performance Mares more Efficiently

Guide to give to your customers.

Man handing woman a bucket with horse in background

Equine Product Reference Guide

A guide to the entire equine product line from Merck Animal Health.


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