Ristaben was more effective than placebo when it was taken alone or in combination with other antidiabetes medicines. In patients taking Ristaben on its own, HbA1c levels fell from around 8.0% at the start of the studies by 0.48% after 18 weeks and 0.61% after 24 weeks. In contrast, they rose by
0.12% and 0.18%, respectively, in the patients taking placebo. Adding Ristaben to metformin reduced HbA1c levels by 0.67% after 24 weeks, compared with a fall of 0.02% in the patients adding placebo. When added to pioglitazone, Ristaben reduced HbA1c levels by 0.85% after 24 weeks, compared with a fall of 0.15% in the patients adding placebo.
In the studies comparing Ristaben with other medicines, the effectiveness of adding Ristaben to metformin was similar to that of adding glipizide. When taken on their own, Ristaben and metformin produced similar reductions in HbA1c levels, but the effectiveness of Ristaben seemed to be slightly lower than that of metformin.
In the additional studies, adding Ristaben to glimepiride (with or without metformin) led to a reduction in HbA1c levels of 0.45% after 24 weeks, compared with an increase of 0.28% in the patients adding placebo. HbA1c levels were reduced by 1.03% after 18 weeks in patients adding Ristaben to metformin and rosiglitazone, compared with a fall of 0.31% in those adding placebo. Finally, they were reduced by 0.59% in patients adding Ristaben to insulin (with or without metformin), compared with a fall of 0.03% in those adding placebo.