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Pharmacological particulars
ATCvet code: QG03DX90.
Pharmacotherapeutic group
Sex hormones and modulators of the genital system,
Pharmacodynamic properties
Altrenogest is a synthetic trienic C21 steroidal progestagen, belonging to the 19-nor-testosterone series. It is an orally active progestagen. Altrenogest decrease blood concentrations of the endogenous gonadotrophins, LH and FSH. As a consequence, it induces the regression of all large follicles
(>20-25 mm) and therefore blocks oestrus or ovulation. During the second half of the treatment period with the product, when all large follicles have regressed, there is a peak in FSH concentration which initiates a new wave of follicular growth. End of treatment is followed by a steady rise in LH concentration, which sustains follicular growth and maturation. These endocrine effects ensure that most mares ovulate during the four day period between days 11 and 14 after the end of the treatment course.
Pharmacokinetic properties
Altrenogest is rapidly absorbed following oral administration and can be detected in blood as soon as 10 minutes after dosing. Maximum serum concentrations are observed 2.5 hours following administration. Altrenogest is extensively metabolised in the liver. The terminal half-life following oral administration is 10.7 hours ± 4.3 hours. Altrenogest is eliminated both via urine and faeces, in similar proportions.