The quality of evidence is downgraded by study limitations (lack of/unclear allocation concealment), by inconsistency (unexplained variability in results), and by imprecise results (few patients and outcome events).
A Cochrane review [Abstract] 1 included 7 studies with a total of 1 558 subjects; 457 were involved in 4 studies of antibiotic medication (roxithromycin 2 studies, azithromycin 1 study, doxycycline 1 study), and 1 101 were involved in 3 studies of beta-blocker (propranolol) medication.
For abdominal aortic aneurysm (AAA) expansion it was only possible to combine 2 of the antibiotic trials in a meta-analysis. Roxithromycin had a small but significant protective effect (MD -0.86 mm, 95% CI -1.57 to -0.14 mm; 2 studies, n=176) compared to placebo. The azithromycin study (n=247) did not show any protective effect for antibiotics and the doxycycline study (n=34) demonstrated a non-significant difference in the 18 month expansion rates of 1.50 mm (doxycycline group) compared to 3.00 mm (placebo group). There was no significant difference in referral to AAA surgery between antibiotics and placebo (OR 0.96, 95% CI 0.59 to 1.57; 4 studies, n=457).
There were no significant differences in AAA expansion (MD -0.08 mm, 95% CI -0.25 to 0.10) or referral to AAA surgery (OR 0.74, 95% CI 0.52 to 1.05) between propranolol and control groups (3 studies, n=1 101). Bronchospasm and shortness of breath were the main adverse effects from the beta-blockers. In one trial the adverse effects were reportedly so severe that the trial was stopped early after 2 years.
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