The paper presents an analysis of clinical symptoms, signs and laboratory data of 330 diabetic patients who developed lactic acidosis after having been treated with biguanides (phenformin, buformin, metformin). From the review of the literature an attempt is made to find special features that predisposed patients to develop lactic acidosis such as accompanying illnesses and additional medications, to describe the course of illness and also the factors that influenced the prognosis. Of the patients that developed lactic acidosis 50.3% died. These patients were older, they suffered more frequently from cardiovascular shock, their acidosis was more severe, the whole blood lactate concentration was higher, and the degree of renal insufficiency was more advanced. From our observations we conclude the the treatment of diabetes mellitus with biguanides should be reserved for specially selected patients.
In order to define clinically relevant lactic acidosis, 12 biochemical variables, eight clinical symptoms and signs, leading diagnoses, and mortality were evaluated prospectively in approximately 2,000 unselected patients with internal diseases, consecutively admitted to the hospital. Patients with incomplete data sets were not considered. Of those patients who repeatedly were admitted to the hospital during the time of the study, only the first admission was included for statistical analysis. In addition to 11 definitions of lactic acidosis given in the literature, sequential cluster analyses of the biochemical variables were used to estimate the incidence of lactic acidosis in 1,467 patients. Depending upon which definition was used, 0.5-3.8% of all patients were classified as suffering from lactic acidosis, with a mortality rate ranging from 30-88%. From this study it is concluded that a limit of less than or equal to 7.35 for pH and of greater than 5-6 mmol/L for the concentration of lactate in whole blood will minimize false-negative or false-positive classifications.
Unlike other pharmacological therapies used in obese type 2 diabetic patients, metformin has been shown to improve glycemic control with lower insulin levels and not to involve weight gain. We therefore examined the effect of adjunct metformin in 13 severely obese type 2 diabetic patients (BMI 39.3 +/- 3.9 kg/m2) in suboptimal glycemic control pretreated with intensified insulin therapy. Patients were randomly assigned to either metformin or placebo treatment (double-blind) for 10 weeks and after a 2 week washout period received the opposite treatment, respectively, for 10 additional weeks. HbA1c decreased comparably during placebo (from 8.1 +/- 0.4 to 7.6 +/- 0.3%) and metformin (from 8.5 +/- 0.4 to 7.4 +/- 0.3%, p = 0.29 vs. placebo). Changes in fasting glucose levels were also not different between placebo (from 9.3 +/- 0.7 to 9.5 +/- 0.7 mM) and metformin (from 10.3 +/- 0.5 to 9.5 +/- 0.6 mM, p = 0.44 vs. placebo). Total exogenous insulin requirements decreased from 53 +/- 10 to 35 +/- 7 units during metformin treatment (p = 0.02 vs. placebo). Changes in fasting insulin levels during placebo and metformin treatments were not different (p = 0.11). Metformin had no effect on body weight and serum triglycerides but marginally decreased serum cholesterol levels (from 239 +/- 18 to 211 +/- 14 mg/dl, p = 0.005, p = 0.08 vs. placebo). During the oral glucose tolerance test no differences were observed in the areas under the curve for glucose and insulin while that for C-peptide showed a tendency to increase during metformin administration. We conclude that addition of metformin to insulin treatment in severely obese type 2 diabetic patients improves glycemia but not hyperinsulinemia in comparison to intensive insulin therapy alone. With adjunct metformin, approximately 30% less exogenous insulin is required. With respect to glycemia and lipids, adjunct metformin can be a reasonable treatment alternative in selected obese patients with type 2 diabetes already on intensive insulin therapy.
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