Altrenogest (or allyltrenbolone) is a synthetic trienic C21 steroidal progestomimetic, belonging to the 19-nor-testosterone series. It is an orally active (pro)gestagen. Like all steroids, altrenogest acts by its liposolubility by penetrating the target cells where it binds to specific receptors.
In veterinary medicine, altrenogest is used in gilts and mares for zootechnical purposes (oestrus synchronization). The recommended dose for gilts is 20 mg/animal/day given orally for 18 consecutive days, and for mares is 0.044 mg/kg bw/day given orally for 10 to 15 days.
Adverse effects of altrenogest appear to be minimal when used at labeled dosages. One study (Shideler et al. 1983) found negligible changes in hematologic and most “standard” laboratory tests after administering altrenogest to 4 groups of horses (3 dosages, 1 control) over 86 days. Occasionally, slight changes in Ca++, K+, alkaline phosphatase and AST were noted in the treatment group, but values were only slightly elevated and only noted sporadically. No pattern or definite changes could be attributed to altrenogest. No outward adverse effects were noted in the treatment group during the trial.
Altrenogest, sold under the brand names Regumate and Matrix, is a progestin of the 19-nortestosterone group which is widely used in veterinary medicine to suppress or synchronize estrus in horses and pigs. It is available for veterinary use in both Europe (as Regumate) and the United States (as Matrix)