Bromocriptine: A Sympatholytic, D2-dopamine Agonist for the Treatment of Type 2 Diabetes

Ralph A. DeFronzo, MD


Diabetes Care. 2011;34(4):789-794. 

In This Article

Phase 3 Efficacy Trials

Four phase 3 trials have evaluated the efficacy of Cycloset versus placebo in the treatment of type 2 diabetic patients.[29,40,41] In all studies, Cycloset was administered in the morning within 2 h of awaking and individuals with atypical day-night work shifts were excluded from study. These four studies included 1) 24-week monotherapy trial (n = 159),[29]2) two 24-week add-on to sulfonylurea trials (n = 494),[30] and 3) 52-week add-on to various oral antidiabetic agents trial[41] (Table 1). Results of these four studies consistently demonstrated a placebo-subtracted decline in HbA1c of 0.5–0.7%. Prior to randomization and after 6 months, type 2 diabetic subjects in the monotherapy and add-on to sulfonylurea studies[29] were admitted to the clinical research center for 12 h (7 A.M. to 7 P.M.) and received standardized meals for breakfast (0700 h), lunch (1200 h), and dinner (1700 h). Serum glucose, insulin, FFA, and triglyceride concentrations were measured prior to and at 1 and 2 h postmeal ingestion. Relative to placebo, Cycloset significantly reduced the fasting, postbreakfast, postlunch, and postdinner glucose concentrations (Supplementary Fig. 4) without change in serum insulin level or body weight. Cycloset also significantly reduced fasting and postmeal serum FFA and triglyceride concentrations (Supplementary Fig. 5).

In the monotherapy and add-on to sulfonylurea studies, a prespecified analysis was performed on Cycloset responders (minimum HbA1c decrease from baseline = 0.3% at week 8) versus the entire Cycloset-treated group (Fig. 2). In monotherapy and add-on to sulfonylurea trials, the decrements in HbA1c from baseline were −0.65 and −0.63, respectively, and responders represented 63 and 65% of the total Cycloset-treated group.[29] The placebo-subtracted difference in HbA1c in responders was 1% in both monotherapy and add-on to sulfonylurea trials (Fig. 2).

Efficacy data also are available from a large 52-week randomized, double-blind, placebo-controlled trial in which Cycloset was added to therapy in poorly controlled (HbA1c >7.5%) type 2 diabetic patients who were taking one to two oral hypoglycemic agents (OHAs).[41–43] Mean baseline HbA1c was 8.3%, mean age 58 years, mean BMI 33 kg/m2; 63% were male. In type 2 diabetic subjects who completed 24 weeks of treatment and who took ≥80% of their medication, the placebo-subtracted decrease in HbA1c ranged from 0.6 to 0.9% and was consistent in subjects failing any OHA, failing metformin ± OHA, failing metformin + sulfonylurea, and failing thiazolidinedione ± OHA (Supplementary Fig. 6).[41–43]


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