Motor side effects of atypical antipsychotic drugs

There are two central issues to consider in assessing the motor side effects of atypical antipsychotic (AA) drugs. The fi rst is the defi nition of what it means to be an AA drug. While one review states that ‘the defi ning characteristic of an AA is its lower risk of inducing EPS [extra pyramidal symptoms] [1]’ there is, in fact, no consensus defi nition [2] of what it means to be ‘atypical’. All anti psychotics approved by the US FDA since clozapine in 1991 have been considered AA by the psychiatric community, despite the fact that there are no guidelines for using this designation. Clozapine is the only drug listed as an AA by the US FDA [3], with the later antipsychotics listed only by their chemical families. While several definitions for AAs have been proposed [2,4,5], the one most commonly considered in the medical community is ‘relative freedom from extrapyramidal side effects’, but what ‘relative’ means may be primarily in the minds of the marketing division of a drug company. The other criteria include: