Drug safety evaluations are not a matter of a one-off proposition. Once drugs are approved, they are often analyzed for safety impact throughout their life cycles. Female birth control drugs such as yasmin and yaz have particularly been under scrutiny for their associated risk of blood clotting and heart health effects, for example.

A new example of this comes in the form of the approved and in-use arthritis medication auranofin. Recent clinical trials showed that the drug may have a beneficial effect on patients suffering from certain amoebic infections that lead to dysentery and other ailments. Dysentery affects thousands of people worldwide, particularly where water quality control is less rigorous or even nonexistent. The studies, conducted in lab animals, suggested a strong enough benefit that auranofin will now enter a new round of human testing to see if it can treat patients with these kinds of amoebic infections safely and effectively. If it can, it will provide an inexpensive means to provide treatment for such ailments.

What sets this apart, is that the drug’s safety in treating patients with arthritis wasn’t under question — the safety tests are for a new use of the medication outside of its normal scope of application. Drugs can be dangerous when used in one way, safe when used in another. Take for example the antidote to the nerve gas, sarin. By itself, the antidote is itself a dangerous poison and will kill someone. In the presence of sarin, it becomes a life-saving tool. The focus of these trials will therefore be to see if auranofin is still safe to use in the presence of amoebic infections of this sort.

The findings show that the drug inhibits the growth of the amoebas in question, meaning that the body will have more time to eliminate the infection before it leads to life-threatening complications from dehydration and malnutrition that often accompany amoebic dysentery.