We have compared our single-dose protocol to the GnRH-a long protocol using a depot formula of Triptorelin in a prospective randomized study (6). A 3:1 randomization was selected including 115 patients in the Cetrorelix group and 36 in the agonist long protocol group. No difference was observed between the GnRH agonist and antagonist groups for demographic and baseline data.
One hundred and four patients (90.4%) out of 115 patients received only one 3 mg dose of Cetrorelix. If the criteria for triggering of ovulation were not reached within four days (the protection period), we administered an additional dose of Cetrorelix (0.25 mg). Only nine (7.9%) of the patients received one additional dose on the morning of the hCG and two patients (1.7%) received two additional doses of 0.25 mg.
Moreover, a total of 18 patients of the Cetrorelix group (15.7%) presented an LH rise (LH > 10 IU/L) on the day of Cetrorelix injection. The administration of the Cetrorelix inhibited LH secretion. Four of them became pregnant (22.2%). These interrupted LH rises seem to have no measurable deleterious effect in this study. Only one patient in the Triptor-elin group (2.8%) experienced an LH surge. None of the 115 patients of the Cetrorelix group experienced an LH surge after the Cetrorelix administration. No LH surge has been reported so far within the four days following the single administration of 3 mg Cetrorelix.
The mean length of stimulation was significantly lower in the Cetror-elix group. The mean number of ampoules was significantly higher in the
Triptorelin group. The E2 levels on the day of hCG were significantly lower in the Cetrorelix than in the Triptorelin group. The total number of follicles >15 and <17mm was higher in the Triptorelin group (5.0 ± 3.9 vs. 3.4 ± 2.6; CI 0.5-2.8). The long GnRH agonist protocol resulted in more oocytes and more embryos as already demonstrated in the literature when compared to other stimulation regimens. However, the percentage of mature oocytes, fertilization rate, clinical and ongoing pregnancy rates, and miscarriage rates were not statistically different between the two groups. The incidence of ovarian hyperstimulation syndrome (OHSS) was lower in the GnRH-nt group. This difference did not reach statistical significance but some patients of the GnRH-a group were cancelled for being at risk of OHSS. Adding these patients brought the difference to significance.
In conclusion, this study has confirmed the efficacy of a single dose of 3 mg of Cetrorelix, administered in the late follicular phase, in preventing premature ovulation as indicated by LH surges. The single-dose protocol is easy to use and assures patient compliance. The 3 mg dose of Cetrorelix was tolerated well, with only mild and transitory reactions at the injection site. This protocol provides a shorter duration of treatment, uses less gona-dotrophins, and has a lower incidence of OHSS. In some of the patients treated with rec-FSH, a decrease in the E2 level is observed after the injection of the Cetrorelix. This was also observed in our first study using a higher dose of Cetrorelix (5 mg) with human menopausal gonadotrophin (hMG) (11). An increase of the hMG dose, on the day of the antagonist administration, suppresses most of these E2 decreases, probably related to the LH suppression but not exclusively (19). However, no difference is observed in our experience in the IVF-ET results in the patients with or without an E2 decrease following the Cetrorelix administration (unpublished results). One study done in an oocyte donor model (20) found a lower implantation rate of embryos coming from oocytes collected in patients with an E2 drop as compared to patients with continuous rise of E2.
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