Table 2. Distribution of Drug Pairs in Intercepted Errors.

Canceled Order	Completed Order	No. Errors	No. Alerts	Error Rate (%)a	Std. Err. (%)
fluticasone	fluticasone-nasal	100	4565	2.19	0.22
metoprolol	metoclopramide	16	9936	0.16	0.04
nitroprusside	nitroglycerin	6	19	31.6	10.7
hydralazine	diphenhydramine	6	4346	0.14	0.06
propranolol	propofol	5	2931	0.17	0.08
nimodipine	famotidine	3	511	0.59	0.34
clonidine	famotidine	3	2350	0.13	0.07
metformin	metronidazole	3	6148	0.05	0.03
fluticasone-salmeterol	fluticasone-nasal	2	3166	0.06	0.04
hydralazine	hydromorphone	2	4346	0.05	0.03
hydralazine	hydroxyzine	2	4346	0.05	0.03
methyclothiazide	methylergonovine	1	1	100	0.00
minoxidil	minoxidil-topical	1	48	2.08	2.06
tenofovir	atenolol	1	101	0.99	0.99
metolazone	metoclopramide	1	132	0.76	0.75
ibandronate	ibuprofen	1	133	0.75	0.75
methyldopa	methylprednisolone	1	138	0.73	0.72
Actonelb	Actos	1	150	0.67	0.66
felodipine	Feldene	1	177	0.57	0.56
nimodipine	morphine	1	511	0.20	0.20
paroxetine	pyridoxine	1	1071	0.09	0.09
tiotropium	tenofovir	1	1581	0.06	0.06
nifedipine	prednisone	1	2111	0.05	0.05
clonidine	ranitidine	1	2350	0.04	0.04
lansoprazole	alprazolam	1	2381	0.04	0.04
propranolol	lansoprazole	1	2931	0.03	0.03
amlodipine	amitriptyline	1	3183	0.03	0.03
amlodipine	famotidine	1	3183	0.03	0.03
atorvastatin	multivitamin	1	3204	0.03	0.03
hydralazine	chlorzoxazone	1	4346	0.02	0.02
sertraline	tetracycline	1	4529	0.02	0.02
levothyroxine	levofloxacin	1	5642	0.02	0.02
hydrochlorothiazide	hydrocortisone	1	6040	0.02	0.02
hydrochlorothiazide	hydroxyzine	1	6040	0.02	0.02
metformin	metoprolol	1	6148	0.02	0.02
metformin	multivitamin	1	6148	0.02	0.02
metoprolol	ketorolac	1	9936	0.01%	0.01%
metoprolol	metronidazole	1	9936	0.01%	0.01%
simvastatin	simethicone	1	13625	0.01%	0.01%

^aThe interception rate is the number of errors (confirmed by clinician chart review) divided by the total number of alerts for that drug.

^bIn this pair, at the time of the alert, the branded names were most common, >90%.