Ziprasidone and the QTc interval: pharmacokinetic and pharmacodynamic considerations

Many psychotropic medications might cause prolongation of the QTc interval; however, antipsychotics have recently come under increasing scrutiny in this regard. Ziprasidone, a newly marketed second-generation antipsychotic, was initially delayed in approval by the FDA due to its propensity to prolong the QTc interval in patients with schizophrenia. While ziprasidone does prolong the QTc interval, safety, concomitant medication, and overdose data present little reason to consider ziprasidone a major risk factor for Torsades de Pointes thus far. The paucity of data regarding this agent, however, and its use in those with additional risk factors for QTc-interval prolongation are striking. The risk for this phenomenon has not been studied in patients with concomitant disease states that might be associated with QTc-interval prolongation or in those taking metabolic inhibitors which might inhibit aldehyde oxidase. Little is known about a major metabolic route of ziprasidone, oxidation by aldehyde oxidase. Finally, experience with other agents associated with QTc-interval prolongation raises the possibility that both the type and number of individuals studied to date might not be sufficient to reveal problems with ziprasidone. This paper will review the literature concerning real and theoretical implications of pharmacokinetic and pharmacodynamic interactions with ziprasidone, particularly with regard to these effects on the QTc interval.