Letrozole (Femara) is an aromatase inhibitor approved for treating advanced breast cancer and has been shown to be better than Clomid for ovulation induction. Compared with Clomid, Letrozole produces both higher pregnancy rates and fewer side effects. Importantly, Letrozole also rarely stimulates more than one follicle, decreasing the risk of multiple gestations.
It is administered at dosage of 2.5 mg to 5 mg from day 2 of the period for 5 days with ultrasound scans to check for ovulation monitoring.
Many physicians will not prescribe Letrozole because of concerns from a 2005 report from some Canadian fertility doctors suggesting a possible higher incidence of birth defects in pregnancies from using Letrozole. This study was from a small group of pregnancies and the study has been severely criticized for having an improper design.
The manufacturer of the drug has apparently not filed for FDA approval to use it for infertility. However, physicians often use medications in an “off label or non-licensed ” way. When the off label use is safe and effective it is perfectly legitimate.
In a new study by Dr. Tulandi and Dr. Robert Casper from Department of Obstetrics and Gynecology at the University of Toronto examined a total of 911 babies whose mothers were treated for infertility with either Letrozole or Clomid from 2001 to 2005 and found it to be safe.
Though there are good studies about the safety this drug is not licensed for ovulation induction in the UK .
We can offer this drug in specific cases where it may improve the chances of pregnancy and the unproven risks are accepted.
We do not suggest a patient is given Letrozole for longer than 6 months.