Plasma and follicular fluid concentrations of LHRH antagonist cetrorelix (Cetrotide®) in controlled ovarian stimulation for IVF

Cetrorelix was administered in differing daily dosages for controlled ovarian stimulation. The dosage levels were 3 mg (9 cycles), 1 mg (19 cycles), 0.5 mg (43 cycles), 0.25 mg (46 cycles) and 0.1 mg (7 cycles). In the 3 mg, 1 mg and 0.5 mg group the respective median plasma concentrations of cetrorelix on the day of oocyte pick-up (OPU) were 2.10 ng/ml, 1.42 ng/ml and 0.88 ng/ml and 1.03 ng/ml, 0.46 ng/ml and 0.49 ng/ml on the day of embryo transfer (ET). In the 0.25 mg and 0.1 mg groups plasma cetrorelix levels were below the limit of quantification. The cetrorelix concentrations in follicular fluid (FF) in the 0.25 mg group were detectable in only 14 out of 44 samples, while in the 0.1 mg group no detectable concentrations could be obtained. We also examined 80 cycles after single doses of 5 mg (7 cycles), 3 mg (42 cycles), and 2 mg (31 cycles) cetrorelix. On the day of OPU the respective median plasma concentrations of cetrorelix were 0.57 ng/ml, 0.62 ng/ml, and 0.56 ng/ml, and 0.61 ng/ml and 0.28 ng/ml on the day of ET in the 5 mg and 3 mg groups. In the 2 mg group, the plasma concentrations fell to below limits of quantification in 8/9 samples on the day of ET. In 26 out of 27 FF samples cetrorelix was detectable in the 3 mg single dose group (median level: 0.69 ng/ml).