(Ceva Animal Health) Altresyn Solution 0.22% is indicated to suppress estrus in mares. Suppression of estrus allows for a predictable occurrence of estrus following drug withdrawal. Each ml of Altresyn Solution contains 2.2 mg of altrenogest, an active synthetic progestin. The recommended dosage of Altresyn is 1 ml per 110 lbs. body weight given once daily for 15 consecutive days. Altresyn is for administration orally on back of mare’s tongue or applied to usual grain ration. Protective gloves should be worn when handling product; women who are pregnant or suspect they are pregnant should not handle Altresyn Solution 0.22%. Altrenogest.