Aripiprazole-Induced Acute Dystonia

To the Editor: Aripiprazole, the new-generation atypical antipsychotic that is a dopamine system stabilizer, is known for its low propensity to cause extrapyramidal symptoms (1) . Although several reports of dystonia associated with the use of newer atypical antipsychotics are accumulating, a thorough PubMed search through Nov. 6, 2005, did not reveal a single such case induced by aripiprazole. We report a case of acute dystonia observed during aripiprazole therapy.

In our case report, Mr. A had two known risk factors for dystonia, i.e., being young and male (1) . Additionally, we propose the following neurobiological mechanisms that either alone or in combinations could have resulted in acute dystonia with aripiprazole.

First, aripiprazole—unlike clozapine, which does not induce acute dystonia—lacks protective anticholinergic action (1) . This was supported by the fact that, in our case, dystonia resolved with anticholinergic medicines. Second, aripiprazole’s action on the D ₃ receptor and antagonism of 5-HT ₆ and 5-HT ₇ receptors is still unknown (1) and could play a potential role. Third, postsynaptic dopamine hypersensitivity was found in bipolar patients (4), which may be a significant factor. Fourth, the possibility of complex drug interaction of aripiprazole with divalproex cannot be eliminated. Last, preclinical studies found inhibitory action of aripiprazole on serotonin transporter (1), which could potentially alter dopamine balance in the basal ganglia region.

In short, our case report reveals that even aripiprazole may cause rare dystonia in vulnerable individuals, despite having a favorable receptor profile. However, this side effect is amenable to conventional anticholinergic treatment.