Clozapine: a hypothesised mechanism for its unique clinical profile.

Clozapine's clinical profile is unique among antipsychotic drugs. What makes it different? For almost two decades researchers have been attempting to answer this question. Based on various data, many hypotheses have been proposed. Using electrophysiological techniques we have found that clozapine, like typical antipsychotic drugs, inactivates most midbrain dopamine cells secondary to the induction of depolarisation block. However, unlike classical antipsychotic drugs, clozapine does not inactivate the nigrostriatal dopamine system. Based on these and other findings the hypothesis of 'depolarisation block' is reviewed and presented as an explanation for clozapine's unique clinical profile. Research data both for and against the hypothesis are then discussed.