REGUMATE EQUINE, a veterinary medicinal product for horses, should be used with caution

The French Agency for Veterinary Medicinal Products, within ANSES, is calling for continued vigilance when administering the veterinary medicinal product REGUMATE EQUINE to control the oestrus cycle in mares. Because of its hormonal action this product can cause adverse effects, especially in women who administer it to their horses. Therefore, women who are pregnant or likely to become pregnant should not administer the product themselves. In addition, the Agency reminds users of the importance of observing the product’s special precautions for use.

Altrenogest is a synthetic progestogen used as a veterinary medicinal product to facilitate reproduction in the equine and swine sectors. In the equine community, this synthetic hormone is found in the medicinal product REGUMATE EQUINE, which is widely used both by professional horse breeders to stop or synchronise the oestrus cycle in mares, and by horse owners or keepers to reduce oestrus symptoms during equestrian competitions. In France, as many as 30,000 treatments based on this drug are administered to mares each year.

Adverse reactions, especially on women’s menstrual cycles

Like all progestins, altrenogest can cause adverse reactions in the persons who regularly administer the treatment. Repeated contact with the product may lead to negative effects on the female reproductive system, such as disruption of the menstrual cycle, uterine or abdominal cramping, and prolongation of pregnancy. It may also potentially cause loss of libido in men. Other signs may also occur in all persons administering the product, including headache, fever, abdominal pain, nausea, diarrhoea, vomiting and hives.

The United States Food and Drug Administration (FDA) reported 130 cases of altrenogest-induced adverse reactions between October 1987 and May 2018, 121 of which were in the equine community. In France, reported cases have been rare, with only eight reported cases since 2002, including three in the equine sector, which suggests, according to ANSES, that cases are under-reported. This is because people do not spontaneously make the link between their symptoms and the fact that they have been exposed to the drug. ANSES therefore calls for continued vigilance to prevent these risks.

Avoid direct contact with the skin

ANSES recommends that some sections of the population should avoid all contact with the product and should not administer it themselves. This applies to:

  • women who are pregnant or likely to become pregnant;
  • persons with known or suspected progesterone-dependent tumours;
  • persons with thromboembolic disorders.

In addition, ANSES reminds users of the importance of observing the special precautions for use as set out in the REGUMATE EQUINE package leaflet, about avoiding direct contact with the skin. Users must wear gloves and protective clothing when handling the product and must wash their hands after treatment.

Special warning regarding the choice of gloves:

  • use undamaged vinyl, neoprene or nitrile gloves;
  • do not use porous latex gloves, which may let the product pass through;
  • use single-use gloves to avoid contact with the product when handling already soiled gloves.

What to do in case of accidental contact

  • wash the skin immediately with soap and water;
  • in case of accidental contact with the eyes, rinse thoroughly with water for about 15 minutes.

Report an adverse reaction in humans following the use of a veterinary medicinal product here: