A previous clinical trial found that tamoxifen, taken for five years, reduced the risk of developing invasive breast cancer by about 50% in post-menopausal women who were at increased risk of getting the disease.
Another trial found that five years of raloxifene reduces breast cancer risk in such women by about 38%.
Under the new plans, high risk post-menopausal women could be offered the drugs for a period of five years unless they have a history of thromboembolic disease or endometrial cancer.
More top news
1,209 people were found guilty of 'trolling' offences in 2014 - and 155 have been jailed.
Critics are ambivalent to this year's slate of winners, who were picked in part by American directors Joel and Ethan Coen.
1.5m European citizens will miss out on the chance to vote on whether Britain stays in or quits the EU.