Drug-Drug interactions (DDIs)
Of the 954 QTcP-inducing drugs prescribed, 618 (64.8%) had interactions with other drugs; 10.4% (n=64) were major DDIs, 29.3% (n= 181) were moderate DDIs, and 60.3% (n=373) were minor DDIs (Table 3 ). Prescriptions with minor polypharmacy were less likely to have major DDIs compared to those with major polypharmacy (OR 0.61; 95%CI 0.23-0.97; p=0.02), and prescriptions for patients with no co-morbidity were less likely to have major DDIs compared to those prescribed for patients with co-morbidity (OR 0.72; 95%CI 0.44-1.23; p=0.04). Differences in types of the clinic or clinic location were not significantly related to major DDIs proportion. Of 618 identified DDIs, 257 (41.6%) had good documentation, 201 (32.5%) had proven documentation, and 160 (25.9%) had fair documentation. Examples of DDIs were listed in Table 4.