Table 4.

Confounder-adjusted outcome occurrence rate ratios for the association between serious bleeding and warfarin when used concomitantly with a sulfonylurea or metformin

Outcome	Person-days during observation time	Number of outcomes during observation time	Precipitant drug	Person-days during precipitant-exposed timea	Number of outcomes during precipitant-exposed time	Rate ratiob	95% CI
Serious bleedingc	1,433,447	7,388	glimepiride	101,700	496	0.93	0.75, 1.15
			glipizide	259,066	1,276	0.97	0.84, 1.13
			glyburide	183,101	913	0.89	0.76, 1.06
			metformin	385,586	1,757	0.85	0.76, 0.96
Gastrointestinal bleeding	1,303,047	6,419	glimepiride	92,882	441	0.98	0.78, 1.24
			glipizide	236,553	1,090	0.96	0.82, 1.13
			glyburide	162,723	756	0.89	0.74, 1.06
			metformin	343,808	1,487	0.92	0.81, 1.05
Non-traumatic intracranial hemorrhage	141,179	996	glimepiride	9,457	58	0.68	0.37, 1.25
			glipizide	25,667	191	1.04	0.70, 1.55
			glyburide	22,488	161	0.88	0.57, 1.36
			metformin	43,526	276	0.51	0.36, 0.71

CI: confidence interval (based on a two-tailed test).

^aPrecipitant-exposed time: days of warfarin-precipitant drug concomitant use during observation time since the initiation of the concomitant use.

^bRate ratio: [(outcome occurrence rate during precipitant-exposed time) / (outcome occurrence rate during precipitant-unexposed time)], for each warfarin-precipitant drug pair.

^cSerious bleeding as a composite outcome; occurrence of gastrointestinal bleeding or non-traumatic intracranial hemorrhage or both.