Figure 1.

The structures of the hypocholesteraemic drug, triparanol, which was withdrawn from the market in the late 1950s because it caused cataracts in patients, and the first nonsteroidal antioestrogen, ethamoxytriphetol or MER25. MER25 was too toxic and not particularly potent, so clinical studies were discontinued in favor of the triphenylethylene, clomiphene. This drug is a mixture of cis and trans geometric isomers and is used for the induction of ovulation in subfertile women. Tamoxifen is the pure trans isomer eventually developed for the induction of ovulation in subfertile women and for the treatment of breast cancer in elderly women.