Cyclosporin(e) or Sandimmun(e) (both without the "e" in the US) produced by Sandoz Pharmaceuticals is a classic example of a drug being developed for one use, which is then "borrowed" for the treatment of other, unrelated, conditions. This powerful immunosuppressant was originally developed for use after organ transplants by suppressing the immune system, it makes it less likely that a donated organ will be identified and rejected as, literally, a "foreign body".

Now, however, cyclosporine is beginning to be used for many conditions such as psoriasis and others thought to be triggered by an over sensitive immune system response.Not surprisingly for a potent drug developed for use in the extreme situation of a transplant, cyclosporine brings with it a whole host of dangerous side effects. It has been shown to be effective in treating refractory psoriasis (New Eng J Med, 31 January 1991), but patients may be merely swapping one severe but non life threatening skin condition for another that is far worse skin cancer. As well as skin cancer, cyclosporine has been shown to cause other types of malignancies including lymphoma (cancer of the lymph nodes, thymus, tonsils and spleen).

It is also associated with liver and kidney damage. The American Physicians' Desk Reference warns that of those transplant patients receiving cyclosporine who suffer kidney damage as a result:: "From 5 per cent to 10 per cent . . . will fail to show a deduction in a rising serum creatinine [a waste product of the body's metabolism] despite a decrease or discontinuation of cyclosporine therapy." In other words, the damage to kidneys is permanent. Inevitably, because cyclosporine suppresses the immune system, the body becomes more susceptible to infections. There have also been reports of some adults and children suffering convulsions while taking the drug. And one in 1000 patients have experienced anaphylactic reactions, including flushing of the face and chest, acute respiratory distress and wheezing, rapid pulse rate and high blood pressure.