Oral Solution for Horses

  • Trust REGU-MATE® (altrenogest), the pioneer product
  • 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


REGU-MATE (altrenogest) Oral Solution for Horses 2.2 mg altrenogest per mL (0.22%) is indicated to suppress estrus in mares. Suppression of estrus allows for a predictable occurrence of estrus following drug withdrawal with ovarian follicles 20 mm or greater. 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.



When handling Regu-Mate® product, the dosing device, or syringes, always use vinyl, neoprene, or nitrile gloves. Latex gloves are not protective. The product may be dosed using Regu-Mate® Equine Dosing Device or a luer lock syringe. Use of the Regu-Mate® Equine Dosing Device is recommended to reduce the risk of human exposure. Follow all instructions when using the dosing device. Do not use any dosing device other than the Regu-Mate® Equine Dosing Device.

For use with Regu-Mate® Equine Dosing Device, first assemble the device according to directions supplied with the Regu-Mate Equine Dosing Device. Remove the shipping cap and seal on Regu-Mate (altrenogest) bottle. Store the cap in a clean and dry location. Apply downward force and fasten the quick connect cap with dip tube onto the product bottle. The flexible dip tube will contact the bottom of the product bottle and bend slightly. Turn the dose selection dial to 15. Hold the dosing device vertically with the nozzle on the top. Direct the opening of the nozzle away from any person and cover it with absorbent material. Slowly squeeze and release handle until air in the barrel is expelled and product starts to come out. Prime the device by expelling two (2) doses of 15 mL of product into a waste container or absorbent material. (Re-prime the dosing device by expelling two (2) doses if air is observed inside the barrel after switching to a fresh bottle or during dosing period). Set the dose according to DOSAGE CHART provided herein by turning the dose selection dial. The dosing device is ready for use. Refer to the Regu-Mate® Equine Dosing Device label for equipment cleaning instructions.

For use with a luer lock syringe, 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 and return bottle to upright position before detaching syringe. (Note: Do not remove syringe while bottle is inverted as spillage may result.) Replace cover on bottle dispensing tip to prevent leakage. Syringes used for administration should be replaced frequently and disposed of in a secure manner to prevent exposure to the product.


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.

Important Safety Information

Regu-Mate® is contraindicated for use in mares having a previous or current history of uterine inflammation. Natural or synthetic gestagen therapy may exacerbate existing low-grade or “smoldering” uterine inflammation into a fulminating uterine infection in some instances. Do not use in horses intended for human consumption. Avoid skin contact. Regu-Mate® is absorbed through unbroken skin, and exposure may result in serious side effects to both women and men. Wear vinyl, neoprene, or nitrile gloves when handling or administering Regu-Mate®, or when touching contaminated surfaces or equipment. Latex gloves are not protective. PREGNANT WOMEN OR WOMEN WHO MAY BE PREGNANT SHOULD NOT HANDLE REGU-MATE®. WOMEN OF CHILDBEARING AGE SHOULD EXERCISE EXTREME CAUTION WHEN HANDLING THIS PRODUCT. Regu-Mate® is readily absorbed through the skin and could lead to a disruption of the menstrual cycle or prolongation of pregnancy. Accidental spillage on the skin should be washed off immediately with soap and water. Keep out of the reach of children. For complete safety information, refer to the product label.


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

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

Guide to give to your customers.


Equine Product Reference Guide

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


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