Biomedical subjects
Publications and source records attributed to H Samimi.
Different doses of glibenclamide and of 4-transhydroxy-glibenclamide (main metabolite in man) were administered i.p. to rats and blood glucose was measured. The comparison of the doses capable of producing a 30% decrease of the glycemia shows that 4-trans-hydroxy-glibenclamide is about 6.5 times less potent than glibenclamide in our experimental conditions.
Renal insufficiency is a factor which predisposes to hypoglycemic accidents in subjects treated with hypoglycemic sulfonylureas. Glibenclamide (glyburide) is eliminated from the body mainly by metabolism, with the result that renal insufficiency has little effect on its biotransformation. In order to determine to what extent the retention of the metabolities intervenes in such hypoglycemic accidents, rats with ligatured ureters received intraperitoneal injections of 1 mg/kg glibenclamide or hydroxy-glibenclamide (the main metabolite), or of saline. For each animal there was a control animal which had undergone a simulated operation. For six rats with renal insufficiency, glibenclamide caused hypoglycemia of the same intensity as in the control group but more prolonged. With hydroxy-glibenclamide the glycemia was signficantly lower than in the control group. Hydroxy-glibenclamide has an obvious hypoglycemic activity which represents 1/6 of that of the parent drug, but 50--100 times that of tolbutamide. Its retention contributed to the intensification and prolongation of the hypoglycemic effect of glibenclamide in rats with renal insufficiency.
Glibenclamide, a hypoglycemic sulfonylurea, is extensively metabolized by the body and eliminated primarily in the form of its hydroxylated derivatives. The major metabolite, 4-trans-hydroxy-glibenclamide, is usually cleared rapidly from the bloodstream, but in certain pathological states (e.g. renal failure) blood levels of this product may increase. A protocol therefore was designed to test the hypoglycemic potency of this important metabolite in rats. Various quantities were injected intraperitoneally, and alterations in blood glucose concentrations were measured during a 5-hour period and compared to those in animals similarly treated with glibenclamide and in saline-injected controls. Using the dose capable of decreasing blood glucose levels by 30% (ED30) as a comparative index, it was observed that the metabolic has a marked hypoglycemic activity; though 6--7 times less potent than the parent drug, 4-trans-hydroxy-glibenclamide is nevertheless more potent than tolbutamide. Thus, while the glibenclamide metabolite probably has little influence on blood glucose when its clearance is normal, this product may exert marked effects if allowed to accumulate in the blood, as for example in renal failure. Finally, the role of such sulfonylurea metabolites should be taken into account when attempting to explain the occasional excessive and sustained hypoglycemia which occurs in some diabetic patients treated with these drugs.
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