Distribution and pharmacokinetics of the gonadotrophin releasing hormone analogue (Gn-RH analogue) dalarelin in rats.

The dynamics of concentration changes for dalarelin in the blood as well as in organs and tissues at different times from its administration to female rats as a single subcutaneous injection, was observed. Also, the basic pharmacokinetic parrameters were determined. The maximum concentration of dalarelin in the blood (Cmax), which was 261.5 pg/cm3, was observed at the maximum time (tmax) 30 min, after its subcutaneous administration. The simplest equation describing the observed concentration changes for dalarelin in the blood is a tri-exponential equation of an open two-compartment model. The obtained results indicate that dalarelin is selectively captured by the pituitary as well as by the non-specific organs: heart, brain and uterus. It allows us to conclude that it has a wider spectrum of activity.