Chicago: Three in 10 women take the common breast cancer drug Femara to treat infertility, even though it could increase risks to the baby, US researchers said on Friday.
They said the drug is often prescribed "off-label" to treat infertility, even though it is classified by the US Food and Drug Administration as posing a pregnancy risk.
And a study of health claims suggests policies by health insurers to only pay for the drug`s approved uses could improve both the care and safety of the women who take it.
Novartis`s Femara or letrozole is approved to treat post-menopausal women who have hormone-receptor positive breast cancers, in which a hormone is driving the cancer.
The drug, which in a class of drugs known as aromatase inhibitors, works by blocking the production of estrogen in postmenopausal women.
Femara has also been studied as a treatment for infertility, but so far there has not been enough evidence to show that it is safe and effective, according to researchers at the pharmacy benefit company Prime Therapeutics, which presented the findings at the Academy of Managed Care Pharmacy meeting in San Diego.
In one Canadian study in 2005, a team found nearly a three-fold increase in the risk of birth defects in a group of 150 babies born after letrozole treatment, and the company has warned doctors against using the drug to treat infertility.
Once drugs are approved by the FDA, doctors are free to prescribe them as they see fit.
Doctors that treat infertility say they use the drug in women with ovulation problems.
According to a website for the Advanced Fertility Center of Chicago, when the enzyme aromatase is blocked by the drug it causes estrogen levels in young women to fall, triggering the release of follicle stimulating hormone or FSH, which causes women to ovulate.
And they said the Canadian study was too small, and its trial design has been seen as flawed.