Trimetazidine is a drug with cardioprotective properties used in coronary artery disease. Its effect has been attributed to the inhibition of the long chain fatty acids intramitochondrial transport via carnitine-palmitoyl-transferase-1. Clinical evidence supports the possibility that trimetazidine is able to improve the fasting glycemia in diabetic patients. For this reason, the objective of the present study was to determine the effect of trimetazidine on serum glucose of Sprague-Dawley rats with fasting hyperglycemia. All animals received water and food "ad libitum." Blood glucose was measured weekly to confirm fasting hyperglycemia in rats. The rats were treated for 1 month with trimetazidine (1 mg/kg), and blood samples were collected (in the fasting period) on the last day of treatment (the 30th day); and then on the 15th day posttreatment, measurements of plasma glucose were taken. Fasting plasma levels after 30 days of trimetazidine administration decreased significantly from 141.2 +/- 3.3 mg/dL (pre-drug) to 120.9 +/- 5.8 mg/dL (P<0.01). 15 days after the end of treatment, fasting plasma glucose levels (137.0 +/- 7.0 mg/dL) were close to the pretreatment levels but significantly different (P<0.05) from levels on day 30 of treatment. These data suggest that trimetazidine improved blood glucose utilization in rats with fasting hyperglycemia.