If you are taking the breast cancer pill, tamoxifen, you may need to consult your doctor. Several reports released today stated that the side effects are causing women to stop taking the pill. Side effects include "mysterious aches and pains".

Tamoxifen is suppose to reduce the risk of breast cancer returning. Reports say that tamoxifen is 50 percent effective if taken properly. 16 percent of women who do not take Tamoxifen as directed are more likely to die.

"We need to acknowledge that this is something that is truly affecting our patients," Dr. Julie Gralow of the University of Washington School of Medicine told reporters in a telephone briefing.

Tamoxifen transformed breast cancer therapy when it was shown to reduce the risk of cancer coming back by close to 50 percent. But the pill, sold by AstraZeneca under the brand name Nolvadex and also available generically, raises the risk of death from strokes and endometrial cancer.

A newer class of drugs, the aromatase inhibitors, appear to be safer, but they cannot be taken by women who are not yet through menopause.

Dr. Alastair Thompson of the University of Dundee in Scotland and colleagues looked at the records of 2,080 women treated for breast cancer between 1993 and 2002.

Ten percent of the women failed to fill 30 percent or more of their tamoxifen prescriptions. These women were 16 percent more likely to die over the study period than women who took the pills as directed.

Although tamoxifen is shown to work best when taken for five years, the women in the study took the drug for an average of just under 2 1/2 years.

"It could well be a question of side effects," Thompson told reporters. "I think most women who take tamoxifen know that it does have very substantial and life-affecting side effects, even if just hot flashes, which can make life a misery."