Perhaps you should try some spelling variations:
22psychotropic drugs » psychotropic drugs, nonpsychotropic drugs, psychotrophic drugs
psychotropic drug » psychotropic drugs
23 therapeutic » 3 therapeutic, 2 therapeutic, 13 therapeutic

Try widening your search to All Fields.

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• The words AND, OR and NOT may confuse the search; try adding quotes: "%((22psychotropic drugs) OR (psychotropic drug)) %23 therapeutic use%22".
• Adding a wildcard symbol may retrieve word variants: %((22psychotropic drugs) OR (psychotropic drug)) %23 therapeutic use%22*.