If Kao et al. had a similar proportion of torsade cases to Pearson, it would represent approximately 2.5 reports of torsade per month in America. Considering there are reportedly around 550,000 patients on methadone at any one time in America (FDA 2010) this is not consistent with Kao et al. who contend that the condition is a major factor in methadone deaths. Furthermore, the figure is consistent with both French adverse reaction reports and a Norwegian mortality survey of methadone patients (Perrin-Terrin 2010, Anchersen 2009).
Dr Krantz is the corresponding and senior author of this paper. His seminal paper on this subject in 2002 failed to separate addiction from pain management cases. This omission may have contributed to confusion about the dose level at which torsade de pointes may be expected to occur due to the extremely high doses of his pain management cases (which were only revealed in a subsequent paper). The mean reported dose across the groups was 397mg daily yet their follow-up paper allowed a calculation of very different mean daily dose levels between the two groups (541mg for 8 pain patients and 269mg for 9 dependency cases).