A total of 47 studies covering nine different subclasses of cardiovascular drugs were included in the review, 38 of which were RCTs. The sample sizes ranged from 5 to 49,673 patients.
For the 38 RCTs study quality (on a scale of 1-5) was scored as 1 (four studies), 2 (13 studies), 3 (11 studies), 4 (six studies) and 5 (one study); three studies were scored as 0 but the implications of this score were unclear. For the nine nonrandomised trials study quality (on a scale of 1-9) was scored as 3 (one study), 4 (two studies), 5 (four studies), 6 (one study) and 8 (one study).
There were no statistically significant differences between the groups for any of the intervention types considered.
The ES for all drug classes (30 studies, n=837) was -0.03 (95% CI: -0.15, 0.08), favouring brand-name drugs.
ESs which favoured brand-name drugs included: diuretics (10 studies, n=135) ES -0.03 (95% CI: -0.28, 0.22); angiotensin converting enzyme (ACE) inhibitors (1 study, n=23) ES -0.09 (95% CI: -0.68, 0.50); statins (2 studies, n=71) ES -0.25 (95% CI: -0.62, 0.12); and warfarin (4 studies, n=138) ES -0.09 (95% CI: -0.33, 0.15).
ESs which favoured generic drugs included antiplatelet agents (2 studies, n=50) ES was 0.21 (95% CI: -0.19, 0.61) and α-blockers (1 study, n=43) ES 0.06 (95% CI: -0.37, 0.50).
Those which favoured neither (ES = 0) included β-blockers (6 studies, n=135) (95% CI: -0.24, 0.25) and calcium channel blockers (4 studies, n=242) (95% CI: -0.53, 0.53).