Abstract

Objective To determine the effect of the number of different drugs with a compliance of at least 70% on recurrent admission for myocardial infarction (MI) in patients with a history of MI.

Design Nested case control study in a dynamic cohort.

Setting PHARMO database that contains pharmacy dispensing records and hospital discharge records on 350,000 Dutch citizens.

Subjects All patients hospitalised for first MI (ICD-9 410) from 1991 to 2000 with at least a 30-day survival after hospitalisation. Cases were admitted for recurrent MI and were matched for age, sex, and year of admission to controls that did not have a recurrent MI.

Main outcome measure(s) Odds ratio with 95% CI for admission for recurrent MI. Exposure was the number of preventive drugs (antiplatelet agents, statins and beta-blockers or ACE inhibitors) used for at least 70% of the time.

Results 389 cases were matched to 2,344 controls. The use of one drug was associated with a 7% odds reduction (95% CI 31% reduction to 26% increase) for admission for recurrent MI. The use of two or three drugs was associated with reductions of 24 and 38% (45% reduction to 6% increase and 3% to 61% reduction respectively). Addition of one drug caused a 14% reduction (2% to 25%).

Conclusions Multiple drug treatment decreases admissions for recurrent MI in patients with a history of MI. Every addition of a drug, regardless of drug class, reduces the risk even further. These results support the treatment strategies as applied in daily practice.