My mother 58 years old is chronic schizophrenic from 25 years , ect was done 25 years ago ..now she initially respond to each antipsychotic with lowest dose  but she can't sustain it after 3-4 months even with the highest dose of that particular antipsychotic ...we have tried resperidon , olanzapine , amisulpride , haloperidol , clozapine with max dose and even the cocktail of all these drug .. initially she responded to each single drug with lowest dose but overtime she does not respond to that drug or we can say she can't sustain the efficacy of any antipsychotic in long time (4-8 month max) ...we can't go for ECT as she is old ...why it is happening ? What this phenomenon is called ? What should be our next approach ? Can we investigate into any synaptic tissue damage ? It is not that she doesn't respond to any antipsychotic but she simply can't sustain in long run even after increasing the dose...