An experimental model of phenformin-induced lactic acidosis in rats

[Physiopathological approach to pathological hyperlactatemia in the diabetic patient. Value of blood metformin]

Type B lactic acidosis, or pathological hyperlactatemia (PHL), is defined by an arterial lactate level greater than 5 mmol X l-1. It is a known and severe complication of diabetes mellitus treated with biguanide hypoglycaemic agents, particularly phenformin which was taken off the French pharmaceutical market in 1977. Metformin, which remains the only biguanide hypoglycaemic agent currently prescribed in France, may also lead to this complication. However it does so less frequently and mostly in the diabetic presenting with renal failure. A few well studied cases showed that PHL could be correlated with excessive metformin blood levels, i.e. a toxic mechanism. In order to find out whether this toxic mechanism was the real cause of PHL in diabetics treated with metformin, a systematic study of metformin blood levels was carried out in 20 such patients. They had all been admitted to a critical care unit presenting with PHL. The results of this study led us to distinguish between two groups of patients. The seven patients of the first group had high metformin blood levels (4.3 to 65.8 micrograms X l-1). In these, renal excretion or extrarenal dialysis lowered or normalized their hyperlactatemia, and six of the seven recovered from PHL. In the second group, with thirteen patients, metformin blood levels were within the normal therapeutic range (0.225 to 3 micrograms X l-1) for seven patients and close to zero for the other six. This second group received the same treatment as the first one. Only three patients recovered, the others all died.(ABSTRACT TRUNCATED AT 250 WORDS)

The mechanism of action of phenformin in starved rats

The ability of phenformin to lower the blood glucose concentration after an intraperitoneal glucose load, with a concomitant increase in blood lactate concentration, indicated that the drug was increasing the rate of anaerobic glycolysis. The results of experiments in which glucose and gluconeogenic precursors were given to starved rats were explained by a hypothesis for the mechanism of action of phenformin involving inhibition of certain NAD+-dependent dehydrogenases. Substrates with NAD+-linked oxidations could be discriminated from those, like succinate, with FAD-linked oxidations, and succinate may be of use in the treatment of clinical lacticacidosis caused by biguanide drugs.

Reversal of diabetic retinopathy by continuous subcutaneous insulin infusion: a case report

We report the case history of a 20-year-old diabetic girl with long-standing poorly controlled disease who presented with severe retinopathic features and who was treated with continuous subcutaneous insulin infusion (CSII). When first seen she had macular oedema and a visual acuity of 6/18 in her only eye, together with multiple blot haemorrhages and intraretinal microvascular abnormalities. Marked reversal of the retinal lesions occurred within 65 days of initiating SCII and after only 36 days of constant normoglycaemia. Subsequent good blood glucose control on conventional subcutaneous insulin injections has been achieved, and the retinopathy remains quiescent with a visual acuity of 6/5. We suggest that CSII may be a potentially useful method of arresting and reversing early diabetic retinopathy.

Continuous subcutaneous insulin infusion:good blood glucose control for up to 4 days

Six insulin-dependent diabetics were studied on their conventional insulin treatment and during continuous, dual-rate, subcutaneous insulin infusion for periods of up to 4 days. Dabetic control, as assessed by mean plasma glucose, range of plasma glucose values, M-value or range of M-values was improved significantly in 5 patients (mean +/- SD plasma glucose concentration on final infusion day 6.9 +/- 1.3 mmol/l, versus 11.3 +/- 3.2 mmol/l on conventional treatment). Once a suitable insulin dose was established blood glucose control could be maintained by continuous subcutaneous insulin infusion using the same daily infusion rate without frequent adjustment. In some case this was less than the daily dose on the conventional treatment. However, glycaemic control in one "brittle" diabetic, with unpredictable swings in blood glucose on her normal regimen, was not improved by continuous subcutaneous insulin infusion. During the period tested there was no sepsis at the cannula implantation site and patients did not find the system uncomfortable or unduly inconvenient.