Determination of antihyperglycemic biguanides in serum and urine using an ion-pair solid-phase extraction technique followed by HPLC-UV on a pentafluorophenylpropyl column and on an octadecyl column.

An HPLC-UV method was established for the determination of metformin and buformin in biological fluids. Metformin was not retained on particles packed in conventional solid-phase extraction cartridges; in contrast, buformin was retained too firmly and not eluted with a solvent for recovery. However, both drugs were retained on particles that had been treated with an ion-pair reagent of heptanesulfonate or dodecylsulfate and recovered almost completely. The recovered fraction was subjected to HPLC on a pentafluorophenylpropyl column which was suitable for the determination of both biguanides in serum and in urine. Limits of quantitation were low enough for clinical use, and reproducibility was high with an RSD of 0.9-2.3%. HPLC on a conventional octadecyl column was suitable only for the determination of buformin in serum since interfering peaks appeared on the chromatograms of urine samples. The method was applied to analysis of some clinical specimens.

A validated HPLC method with ultraviolet detection for the determination of buformin in plasma.

A sensitive and rapid high-performance liquid chromatographic assay is developed and validated for the determination of buformin in plasma. After addition of metformin as the internal standard, the analytes were deproteinated with acetonitrile, washed with dichloromethane, and the resulting supernatant injected. Chromatography was performed at ambient temperature by pumping a mobile phase of 0.03 m diammonium hydrogen phosphate buffer (pH 7, 250 mL) in methanol (750 mL) at a fl ow rate of 1 mL/min through a silica column. Buformin and metformin were detected at 236 nm, and eluted 9.8 and 15.4 min, respectively. No endogenous substances were found to interfere. Calibration curves were linear over the concentration range of 20-2000 ng/mL. The limit of quantitation was 20 ng/mL. The intra- and inter-day relative standard deviation (RSD) was 8.3%, or less, and the accuracy was within 10.1% of the relative error (RE). The method is suitable in pharmacokinetic investigation of buformin.

A new method for determination of buformin in plasma and urine by ion-paired reversed-phase HPLC with ultraviolet detection.

Buformin is a widely used as an antidiabetic agent but its renal excretion is still controversial. A new HPLC method with ultraviolet (UV) detection for the determination of buformin in plasma and urine has been developed. After protein precipitation or dilution, buformin and internal standard phenformin were resolved on an octadecyl silica column and detected by UV detection at 233 nm. Intra- and inter-day coefficients of variation were <9%. The limit of quantification was around 0.05 micro g/ml for plasma and 2.5 micro g/ml for urine.

Fluorometric determination of biguanides in serum by high-performance liquid chromatography with reagent-containing mobile phase.

A simple post-column derivatization method for the fluorometric determination of biguanides (buformin and phenformin) in serum by high-performance liquid chromatography is described. The serum was treated with 4% perchloric acid to precipitate proteins, and the supernatant was directly injected into the column. Synthesized 9,10-phenanthrenequinonesulphonate (PSQ) was used as a fluorogenic reagent and added to the mobile phase. Biguanides were separated within 10 min on a Radial-Pak microBondapak C18 cartridge (10 microns, 10 cm x 8 mm I.D.) by reversed-phase ion-pair chromatography. They were then allowed to react with PQS in an alkaline stream and detected fluorometrically. This method was applied to the analysis of serum from patients with diabetes mellitus.

Buformin concentrations in a case of fatal lactic acidosis.

A fatal case of lactic acidosis in a 84 year old diabetic woman taking buformin is reported. Buformin concentrations in serum, other body fluids and tissues were measured by gas chromatography. Serum buformin concentration at admission was 5.5 mg/l. Postmortem concentrations were: in serum 3.2 mg/l; in lung 2.8 mg/kg wet weight; in heart 3.0 mg/kg; in pericardial fluid 3.5 mg/l; in liver 5.2 mg/kg; in bile 6.3 mg/l; and in kidney 98 mg/kg.

[Lactic acidosis after administration of guanidine derivatives (buformine, phenformine) (author's transl)]. / Lactatacidose und Biguanidtherapie

Three patients are reported on, who at the time of admittance showed a decompensated metabolic acidosis, elevated concentrations of serum lactate and a reduced kidney funktion. All the patients had taken guanidine derivates (phenformine, buformine) because of diabetes mellitus. The serum biguanid concentrations, however, were elevated in only two cases. Therapy of the lactic acidosis has to be directed at the underlying disease. In biguanid incluced acidosis, haemodialysis with simultaneous administration of sodium bicarbonate is indicated.

[Concentration of 14C-1-butylbiguanide in plasma of diabetic patients and its elimination after administration of a new Galenical formulation (author's transl)]. / Plasmakonznetration und Elimination von 14C-1-Butyl-biguanid-HCl bei Diabetikern nach Einnahme der Substanz in einer neuen Zubereitung

The time course of 1-butylbiguanide concentration in plasma and the urinary and fecal elimination of the substance were measured in six female elimination of the substance were measured in six female diabetic patients after oral administration of 100 mg of 14C-1-butylibiguanide hydrochloride as Sindiatil. The mean maximum plasma concentration was 37 mug/100 ml and was reached after about 2 1/2 h. At least semi-maximum plasma concentrations (greater than or equal 18 mug/100 ml) were maintained between the 1st and 8th h after administration. Within 24 h 64% of the administered dose were eliminated (36% via the kidneys, 28% with the faeces). After 3 days a total of 80% had been eliminated, one-half each in urine and faeces, respectively. The average time taken for 50% of maximum renal elimination, and thus of the absorbed quantity, to be excreted was 7.2 h.