http://health.yahoo.com/drug/202545/precaution
Also, because of the way this medicine acts on the body, there is a chance that it might cause other unwanted effects that may not occur until months or years after the medicine is used. Tamoxifen may cause blockages to form in a vein, lung, or brain. In women, tamoxifen may cause cancer or other problems of the uterus (womb). It also causes liver cancer in rats. In addition, tamoxifen has been reported to cause cataracts and other eye problems. Discuss these possible effects with your doctor.
Side Effects: For males only
Less common
decreased interest in sexual intercourse, inability to have or keep an erection, loss in sexual ability, desire, drive, or performance