Table 2.

Risk of cardiac arrest and non-antiarrhythmic QTc-prolonging medication

Use of QTc-prolonging drugs	Cases (n = 140)	Controls (n = 560)	Crude odds ratio (95% CI)	Adjusted odds ratio*(95% CI)
Non-use	98	453	1 ref	1 ref
Current use	42	107	1.8 (1.2, 2.8)	2.1 (1.2, 3.5)
Daily dose
Non-use	98	453	1 ref	1 ref
≤1 defined daily dose	28	78	1.7 (1.0, 2.7)	1.9 (1.1, 3.5)
>1 defined daily dose	14	29	2.2 (1.1, 4.4)	2.5 (1.1, 5.9)
Number of QTc-prolonging drugs
Non-use	98	453	1 ref	1 ref
One drug	33	94	1.6 (1.0, 2.6)	1.8 (1.0, 3.1)
≥2 drugs simultaneously	9	13	3.2 (1.3, 7.7)	4.8 (1.6, 14)
Drug–drug interactions
Non-use	98	453	1 ref	1 ref
QTc-prolonging drugs only	34	99	1.6 (1.0, 2.5)	1.9 (1.1, 3.2)
QTc-prolonging drugs + P450 inhibitors	8	8	4.6 (1.7, 13)	4.7 (1.3, 16)
Type of QTc-prolonging drug used†
Non-use	98	453	1 ref	1 ref
Amitriptyline	4	10	1.9 (0.6, 6.0)	2.0 (0.5, 8.1)
Cisapride	6	21	1.3 (0.5, 3.4)	1.3 (0.4, 4.0)
Clarithromycin	3	7	2.0 (0.5, 7.8)	1.4 (0.2, 8.6)
Cotrimoxazole	9	30	1.4 (0.6, 3.0)	2.6 (1.1, 6.4)
Domperidone	7	15	2.2 (0.9, 5.4)	4.7 (1.4, 16)
Haloperidole	15	18	3.9 (1.9, 7.9)	3.8 (1.6, 9.2)
Promethazine	3	13	1.1 (0.3, 3.8)	1.2 (0.3, 5.4)
Other QTc-prolonging drug	4	9	2.1 (0.6, 6.8)	1.3 (0.3, 5.6)

^*Adjusted for age, gender, cardiac arrhythmias, other cardiac disease, diabetes mellitus, pulmonary disease, total number of current drugs, concomitant use of antiarrhythmic drugs, serum potassium, calcium, magnesium, creatinine, and bilirubine.

^†Some patients used > 1 QTc-prolonging drug, numbers do not add up.