Effect of Bromocriptine-QR Therapy on Glycemic Control in Subjects with Type 2 Diabetes Mellitus Whose Dysglycemia is Inadequately Controlled on Insulin

Objective: The concurrent use of an insulin sensitizer in type 2 diabetes mellitus (T2DM) patients with inadequate glycemic control on basal-bolus insulin may help improve glycemic control while limiting further insulin requirement. Bromocriptine-QR (B-QR), a quick release, sympatholytic, dopamine D2 receptor agonist therapy for T2DM, is a postprandial insulin sensitizer. This study evaluated the effect of B-QR on dysglycemia in T2DM subjects with suboptimal glycemic control on basal-bolus insulin plus metformin.

Methods: The effect of once-daily morning administration of B-QR on dysglycemia was evaluated in 60 T2DM subjects derived from the Cycloset Safety Trial, with HbA1c >7% on basal-bolus insulin plus metformin at baseline, randomized to B-QR (N = 44) versus placebo (N = 16) and completed 12 weeks of study drug treatment. The analyses also included a subset of subjects on high-dose insulin (total daily insulin dose (TDID) ≥70 units; N = 36: 27 B-QR; 9 placebo).

Results: Subjects were well matched at baseline. After 12 weeks of B-QR treatment, mean % HbA1c decreased by -0.73% relative to baseline (p < 0.001) and by -1.13 relative to placebo (p < 0.001). In the high-dose insulin subset, B-QR therapy resulted in % HbA1c reductions of -0.95 and -1.49 relative to baseline (p < 0.001) and placebo (p = 0.001) respectively. Secondary analyses of treatment effect at 24 and 52 weeks demonstrated similar influences of B-QR on HbA1c. The fasting plasma glucose (FPG) and TDID changes within each treatment group were not significant. More subjects achieved HbA1c ≤7 at 12 weeks with B-QR relative to placebo (36.4% B-QR vs 0% placebo, Fisher's exact 2-sided p = 0.003 in the entire cohort and 37% vs 0%, 2-sided p = 0.039 in the high-dose insulin subset).

Conclusion: B-QR therapy improves glycemic control in T2DM subjects whose glycemia is poorly controlled on metformin plus basal-bolus insulin, including individuals on high-dose basal-bolus insulin. This glycemic impact occurred without significant change in FPG, suggesting a postprandial glucose lowering mechanism of action. Cycloset Safety Trial registration: ClinicalTrials.gov Identifier: NCT00377676.