What are they taken for? There are 6 main reasons why post menopausal women with oestrogen sensitive tumours can be prescribed aromatase inhibitors

• To control or shrink an established breast cancer (palliation).  e.g. to control disease which has spread from the breast to another part of the body (metastasised). 
• To shrink a tumour in the breast before surgery (neo-adjuvant therapy).
• Given in a frail or elderly women to control a tumour in the breast without surgery at all (primary therapy).
• In the adjuvant setting (given after the main therapies such as surgery, radiotherapy to improve the cure rate), AI's can be given to patients who cannot tolerate the side effects of tamoxifen. 
• There is also evidence that some women may be better off taking AI's instead of tamoxifen if they are at particular risk of venous clotting (DVT's) or cancer of the uterus.
• Finally they have been shown to be slightly more effective in some women in the adjuvant setting given either up front, switching after 1-3 years or after 5 years particularly women who's cancers were initially aggressive (grade 3) or had spread to the nodes, were HER2+ or only weakly ER +ve.

Possible side effects

Mild feelings of sickness (nausea), are not uncommon but may be relieved by taking your tablet with foods or milk or at night. Mild nausea usually wears off after a few weeks but a walk or jog in the fresh air does wonders for this. 

Flushes and sweats  Sometimes the flushes will gradually lessen over the first few months but some women continue to have them for as long as they take Arimidex. There are a number of ways to help reduce or control hot flushes and sweats. Some women find it helpful to avoid or cut down on tea, coffee, nicotine and alcohol. Evening primrose oil has been reported to be helpful in reducing sweats but it does not work for all women and it is very expensive. There are a lot of calories in Evening Primrose Oil so it may be fattening in some women. Some women have found complementary therapies have helped, and your GP may be able to give you details about obtaining these on the NHS.

Lethargy - Some women feel tired on this drug. The severity can vary but if it affects your quality of life the doctor should be informed, although lethargy does tend to wear off over time. Light and stimulating exercise can help to reduce this. This has to carefully balanced. Although plenty of rest is important, between these times it is better to be active. For example a sleep after lunch may be required but then it would be useful to put on a pair of training shoes and go for walk in the open - preferably in pleasant stimulating surroundings such as a park or riverbank. Although this seems a great effort at first, patients often find their overall levels of fatigue are reduced by light exercise.  

Thrombosis These therapies slightly increase the risk of thrombosis (although not as bad as tamoxifen) - particularly if there is any disease in the pelvis or lower abdomen. Regular exercise encourage the blood to be pumped through the veins and reduce the risk of it stagnating and clotting in the veins.

Loss of bone density Compared to tamoxifen there is a slightly incidence of bone loss which may lead to an increased risk of fractures  after prolonged use. In some instances it is appropriate to monitor the bone density with a scan (dexacan). Certainly it is advisable to exercise regularly and ensure an adequate diet (see lifestyle and aromatase inhibitors) 

Patients may put on weight after taking aromatase inhibitor tablets. Clearly regular light exercise will reduce the risk of weight gain. 

Depression and lower mood - a rare side effect - Exercise increases the bodies endomorphines which elevate mood.

Less common side effects 

• Allergic reactions – which may include skin rashes
• A very mild risk of thrombosis (blood clots) – pain, warmth, swelling or tenderness in an arm or leg or any chest pain must be reported to your doctor immediately. However, this is less of a risk than with tamoxifen.
• Temporary thinning of the hair
• Vaginal dryness, itching.
• Headaches – some people affected by migraine have noticed a change in the pattern of their headaches