“…The potent agents now available are liable to produce side-effects or toxic effects which have to be set against the potential benefits conferred by these drugs. If drug treatment is appropriate the problem is to choose the compound most liable to produce beneficial effects-regardless of whether weightfor-weight it is the most potent drug-which also has the least risk of unwanted effects (Lader, 1967). This is clearly a complex matter and to gather sufficient information to make a reasonable choice requires both adequate trials to demonstrate the drug's clinical efficacy and sufficient clinical experience to discover the incidence and nature of the side-effects.…”