Table 1.

Clinical and demographic characteristics of users of antimicrobials found in the Express Scripts commercial pharmacy claims database between January 1, 2008 and December 31, 2008.

	Any Antimicrobial			High Risk Antimicrobials Only*
	Warfarin Users	Warfarin Non-users	P value	Warfarin Users	Warfarin Non-users	P value
N	110,192	4,458,150		46,928	1,522,425
Mean age**	65.4	45.5	<0 .001	66.2	47.0	<0 .001
Gender (% male) §	52.9	39.6	< 0.001	46.7	30.8	<0 .001
Mean Chronic Disease Score **	7244	2045	<0.001	7287	2169	<0 .001
Mean antimicrobial prescriptions/person**	3.0	2.4	< 0 .001	2.0	1.7	<0.001
Mean prescription length (days)**	12.4	12.0	< 0.001	10.9	9.0	<0 .001

^*High-risk antimicrobials include trimethoprim/sulfamethoxazole, metronidazole, fluconazole, ciprofloxacin, and levofloxacin

^**t-test

^§Chi-squared test