RESULTS
A total of 61 trials reporting 103 comparisons met the selection criteria, which included 26,367 study participants, 15,760 randomized to an intervention drug(s), and 10,607 randomized to placebo. Most OAD agents lowered A1C levels by 0.5−1.25%, whereas thiazolidinediones and sulfonylureas lowered A1C levels by ∼1.0–1.25%. By meta-regression, a 1% higher baseline A1C level predicted a 0.5 (95% CI 0.1–0.9) greater reduction in A1C levels after 6 months of OAD agent therapy. No clear effect of diabetes duration on the change in A1C with therapy was noted.
CONCLUSIONS
The benefit of initiating an OAD agent is most apparent within the first 4 to 6 months, with A1C levels unlikely to fall more than 1.5% on average. Pretreated A1C levels have a modest effect on the fall of A1C levels in response to treatment.