A new era in ovulation induction.
OBJECTIVE
To evaluate the efficacy of aromatase inhibitors in ovulation induction, superovulation, and IVF.


METHODS
A literature search was conducted with the key words "aromatase inhibitor," "letrozole," "anastrazole," "ovulation induction," "ovulation," and "superovulation" in MEDLINE, EMBASE, and the Cochrane Database of systematic reviews.


RESULTS
Ovulation induction with letrozole is associated with an ovulation rate of 70%-84% and a pregnancy rate of 20%-27% per cycle. In one study, ovulation and pregnancy rates with letrozole seemed to be higher than those of anastrazole. In superovulation, letrozole is associated with few developing follicles and thick endometrium. The use of letrozole for superovulation is associated with a pregnancy rate higher than with the use of clomiphene citrate (CC) (16.7% vs. 5.6%). The addition of letrozole to FSH treatment leads to a decreased FSH requirement. The pregnancy rate for treatment with letrozole and FSH was similar to that for FSH alone.


CONCLUSIONS
Aromatase inhibitors are as effective as or superior to CC in ovulation induction and in superovulation. Unlike CC, they do not carry an antiestrogenic effect on the endometrium. Given the advantages of aromatase inhibitors, they can be used to replace CC as ovulation-inducing drugs. Their role in IVF remains to be determined.
Holzer
Hananel
H
Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, Canada.
Casper
Robert
R
Tulandi
Togas
T
D047072:Aromatase Inhibitors / Q000627:therapeutic use; D002996:Clomiphene / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D005260:Female; D005300:Fertility Agents, Female / Q000627:therapeutic use; D005640:Follicle Stimulating Hormone / Q000627:therapeutic use; D006728:Hormones / Q000627:therapeutic use; D006801:Humans; D007247:Infertility, Female / Q000188:drug therapy*; D000077289:Letrozole; D009570:Nitriles / Q000627:therapeutic use; D010060:Ovulation; D010062:Ovulation Induction / Q000379:methods* / Q000639:trends*; D011247:Pregnancy; D018873:Pregnancy Rate; D013480:Superovulation; D014230:Triazoles / Q000627:therapeutic use
D047072:Aromatase Inhibitors; D005300:Fertility Agents, Female; D006728:Hormones; D009570:Nitriles; D014230:Triazoles; D002996:Clomiphene; D000077289:Letrozole; D005640:Follicle Stimulating Hormone