When used alone, both rosiglitazone and pioglitazone have effects similar to comparator drugs on glycosylated hemoglobin (HbA1c) and fasting plasma glucose (FPG), based on the findings from a small number of comparative trials.
When added to another anti-diabetic agent, the effect on HbA1c and FPG is significantly greater than continuing therapy with the other anti-diabetic agent alone. This is consistent with the work of others that shows combining two anti-diabetic agents provides a greater effect than using one alone.
Both drugs were generally well tolerated during the trials reviewed; only a few cases of heart failure and severe hypoglycemia (when added to another agent) were reported. No liver toxicity was observed. Long-term trials are required to evaluate their effect on the development of diabetic complications and long-term safety.