In Reply:We thank Drs. Chong and Mythily for their comments on our article about the effects of antipsychotic medications on cardiac conduction. We agree completely and would like to clarify their points further.
As noted in our article, higher serum levels of these medications may increase risks. Interactions affecting serum levels and increasing the QTc interval may also occur from systems other than the cytochrome P-450 2D6 system, and clinicians need to be aware of this potential. The points about genetic pleomorphism and racial differences are important.
The use of restraints may raise the risks in two ways. As Drs. Chong and Mythily point out, stress and exertion can increase the risk of arrhythmias. Also, patients being restrained are given extra medications, creating further possible risks.