The Food and Drug Administration warned Friday about two drugs approved for use by organ transplant patients to prevent organ transplant injection. CellCept by Roche and Myfortic by Novartis can cause miscarriages and birth defects when used by pregnant women.

It is also common practise to use these drugs “off-label” to treat other immune system disorders, such as lupus, rheumatoid arthritis, and erythema multiforme, according to WebMD.

The new alert was meant, in part, to grab the attention of doctors who prescribe the drugs for unapproved uses such as treating lupus, said Food and Drug Administration spokesman Christopher Kelly.

Roche spokesman Christopher Vancheri said the company had sent a letter to doctors when the “black box” warning, the strongest type for prescription drugs, was added last year.

In October 2007, the FDA received reports of miscarriages and infants born with ear and mouth birth defects after their mothers took Roche's CellCept. It led the federal agency to add its most serious “black box” warning to CellCept and a similar Novartis AG drug, Myfortic.

Data from a U.S. pregnancy registry showed 15 miscarriages and four birth defects among 33 pregnancies with exposure to CellCept, Vancheri said.

The FDA urges women to discuss pregnancy issues with their doctors, to tell them if they are planning a pregnancy and using MMF (the active ingredient in CellCept) or MPA (the active ingredient in Myfortic).

The FDA urges women to use two forms of effective birth control if they are taking MMF or MPA and to start using two forms of birth control four weeks before taking MMF or MPA continue until six weeks after they stop taking the medicine.

“As patient safety is of the utmost importance to Roche, we continue to work closely with the FDA to develop and implement means to mitigate the risks of fetal exposure,” Roche spokesman Chris Vancheri tells WebMD in an email.