Table 3.

Prevalence of potentially serious drug–drug interactions and regression analyses for risk of interaction

	FC (n=151 632)	FDC (n=307 833)
Drug–drug interaction, n (%)	20 206 (13.33)	28 477 (9.25)
ARB	4905 (3.23)	8706 (2.83)
ACE inhibitor	5114 (3.37)	7623 (2.48)
Beta blocker	78 (0.05)	43 (0.01)
Calcium channel blocker	12 775 (8.43)	16 378 (5.32)

	Relative risk (95% CI)	P values
Unadjusted regression	0.69 (0.66 to 0.73)	<0.001
Adjusted regression*	1.00 (0.94 to 1.05)	0.934
Propensity score-matched regression†	1.09 (1.03 to 1.15)	0.005
As above, adjusting for covariates with an SMD >0.10	1.07 (1.01 to 1.13)	0.030

*Adjusted for patient age and gender, type of combination product (ARB, ACE inhibitor or beta blocker), and total number of antihypertensive defined daily dosages (DDD) in the FC/FDC, number of other antihypertensive prescription items, number of other cardiovascular drugs, number of antiplatelet/anticoagulant drugs, number of cholesterol drugs, number of diabetes drugs and number of other prescribed items.

†Propensity score generated from logit model including all covariates adjusted for in *.

ARB, angiotensin II receptor blockers; FC, free combination; FDC, fixed-dose combination; SMD, standardised mean differences.