Nolvadex is an anti-hormonal medicine and works primarily against the cancers that are stimulated by female sex hormones called oestrogens:

• Nolvadex stops the action of the hormone oestrogen, a natural chemical signal produced by the body, by preventing it from attaching itself (binding) to sites (called receptors) on cells, including cancer cells.
  
  
• Oestrogen is known to encourage the growth of many cancerous tumours of the breast.
  
  
• By stopping the actions of oestrogen, Nolvadex is useful in slowing the growth of the tumour and may cause it to shrink.
  Nolvadex can be used in both pre and post-menopausal women.

Nolvadex is also useful in stimulating ovulation (release of eggs from the ovaries). In some women this is a problem and here Nolvadex can be used as an aid to fertility treatment.