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There is a constant 1_______ for new drugs. This is because there is a lot we don’t know about human biology, there are still many illnesses we cannot cure, and new illnesses appear all the time while existing medicines lose their effectiveness. New 2_______ are tested on animals, but because animals’ bodies work differently from ours, if a drug works on a caged rat, it does not mean that it will do the same foe a human being. The only way to really know about a new medicine is to test it on people in a 3_______ trial. This is done by first giving it to healthy people to see if it is safe, and then giving it to sick people 4_______ if it works.
need
drugs
clinical
to see
