(Ref: KDT 6/e p430, 431, 432) Extrapyramidal adverse effects of antipsychotic drugs are due to blockade of dopamine receptors. These are less often seen with atypical anti-psychotics like clozapine and risperidone (and more often with classical drugs like haloperidol and chlorpromazine). These effects can be treated with central anticholinergic drugs like benztropine and trihexiphenidyl.