Dissolution enhancement of gliclazide using ultrasound waves and stabilizers in liquid anti-solvent precipitation.

The absorption rate of gliclazide is slow and variable among subjects probably due to poor dissolution from the dosage form. The objective of this study was to enhance the dissolution rate of gliclazide by reducing the particle size. Gliclazide was precipitated from an acetone solution by adding an antisolvent (water) containing stabilizers. A combination of jets (flow rate of 20 ml/min), ultrasound, HPMC 4000, and sodium dodecyl sulfate was used to control particle size and particle size distribution. The effects of concentration of stabilizers, initial drug concentration in solution, time of insonation, antisolvent-to-solvent ratio, and ultrasound power on particle size and particle size distribution were studied. Precipitated drug particles were characterized by laser diffraction particle size analysis, SEM, FTIR spectroscopy, DSC, powder x-ray diffraction and in-vitro dissolution. With increasing almost all the studied parameters, the particle size of gliclazide initially decreased, exhibited a minimum, and then increased. Drug particles of glicazide with a mean particle size of 1.56 ± 0.09 µm and a narrow size distribution (d10/d50/d90 = 0.67/1.67/2.26) were precipitated as compared to unprocessed gliclazide with a mean particle size of 10.67 ± 0.04 µm and a wide size distribution (d10/ds50/d90 = 4.53/9.88/18.03). SEM images indicated changes in the particle morphology. Powder x-ray diffraction patterns and DSC curves indicated no changes in the chemical properties but only decrease in crystallinity and/or particle size. The dissolution rate was enhanced 2.55-fold. In conclusion, drug particles with small size and narrow size distribution were precipitated by selecting favorable process conditions, and dissolution was enhanced several folds.

Chemical analysis of solid-state irradiated human insulin.

PURPOSE: To study the chemical modifications induced upon irradiation of solid human insulin at radiosterilization doses and investigate the influence of the absorbed dose on radiolysis. MATERIALS AND METHODS: Volatile radiolytic products were monitored by gas chromatography coupled with mass spectrometry (GC-MS) and non-volatile products by two different high performance liquid chromatography (HPLC) methods: the formation of higher molecular weight proteins was assessed by size exclusion liquid chromatography whereas assays for related compounds and chemical potency tests were carried out using reverse-phase HPLC-UV. Conformational changes were investigated by measurements of circular dichroism. RESULTS: After gamma irradiation at 10 kGy, the recovery of insulin was 96.8%; higher molecular weight proteins accounted for 0.35% (relative peak area) and other related compounds (including A21 desamido insulin) represented 1.29%. No major structural changes and no volatile radiolytic compounds were detected. CONCLUSION: Human insulin samples irradiated in the solid-state at 10 kGy (gamma rays) and 14 kGy (electron-beam) meet the European Pharmacopoeia requirements and can be considered as quite stable towards radiation from a chemical analysis viewpoint.

Effect of different gamma radiation doses on solid crystalline insulin: hypoglycaemia in diabetic beagle dogs.

The effect of different doses of gamma radiation (25, 50 and 100 KGy) on the solid crystalline insulin was studied. The results showed that there was no significant difference (P > 0.05) between the hypoglycaemic effects of 25 kGy gamma-irradiated and the non-irradiated insulin as indicated by the plasma glucose levels and the relative hypoglycaemia. The exposure of insulin to higher doses of radiations (50 and 100 kGy) resulted in almost the same hypoglycaemic effect, which was however greater than that produced by the 25 kGy gamma-irradiated and the non-irradiated insulin. The DSC thermograms showed that the thermal behaviour of crystalline insulin was not affected by the different doses of irradiation. However, a slight colour change was noticed on samples exposed to 50 and 100 kGy of radiation but not on samples subjected to 25 KGy. In conclusion, while the routinely used dose (25 kGy) of gamma radiation for sterilization does not seem to affect the activity of insulin, higher doses of radiation (50 and 100 kGy) enhance its hypoglycaemic effect.

Studies on the in vitro phototoxicity of the antidiabetes drug glipizide.

The phototoxic antidiabetes drug glipizide (1) is photolabile under aerobic conditions and UV-B light. Irradiation of a phosphate-buffered solution of 1 under oxygen atmosphere produces 4 photoproducts as well as singlet oxygen, which was detected by trapping it with 2,5-dimethylfuran and by the histidine test. The photochemistry of 1 involves cleavage of the sulfonamine and the sulfonamine-R bonds. Red blood cell lysis, photosensitized by glipizide and the products of its aerobic photolysis were demonstrated. The photohemolysis rate was lower for 1 than for its photoproducts. Inhibition of this process on addition of 1, 4-diazabicyclo[2.2.2]octane (DABCO), reduced glutathione (GSH), Vitamin C, sodium azide, superoxide dismutase, and a-tocopherol confirmed the possibility of singlet oxygen, superoxide ion and free radicals participation. Furthermore, in a lipid-photoperoxidation test with linoleic acid the in vitro phototoxicity of glipizide was also verified. A low decreasing cell viability of lymphocytes and neutrophils was observed.

Phototoxicity to sulphonamide derived oral antidiabetics and diuretics. Comparative in vitro and in vivo investigations.

The oral antidiabetics chlorpropamide, glibenclamide, glipizide, gliquiudone, glymidine, tolazamide and tolbutamide, and the diuretics bemetizide, bendroflumethiazide, benzylhydrochlorothiazide, bumetanide, butizide, chlortalidone, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, piretanide, polythiazide, trichlormethiazide, and xipamide were investigated for potential phototoxicity in vitro using a cell culture model, and in vivo in hairless mice. After exposure to broad band UVA, the majority of the substances tested in vitro yielded a phototoxic action leading to loss of culture forming ability. In vivo, all tested substances induced edema or ulceration, and lead to a significantly increase in skin fold thickness of the mouse skin. In all, a number of substances not described to induce clinical photosensitivity nor phototoxicity in vitro or in vivo were detected in our testing. When determining potential photosensitizers, it seems important to utilize different test methods, as not all substances will exhibit action in a given assay.

Photooxidation of troglitazone, a new antidiabetic drug.

Troglitazone (CS-045) is a new oral antidiabetic drug reported to be effective in insulin-resistant diabetes and to show antihypertensive effects. Photooxidation of troglitazone gave the quinone and quinone epoxide as the major final stable products. An intermediate observed by NMR spectroscopy was shown to be the hydroperoxydienone, which is moderately stable at room temperature. The rate constant of singlet oxygen quenching by troglitazone is 2.14 x 10(8) M(-1) s(-1) and the reaction rate constant in acetone-d6 is 8.64 X 10(6) M(-1) s(-1). Only the chroman ring of troglitazone reacts with and quenches singlet oxygen significantly, and its reactivity and products are analogous to those of alpha-tocopherol. The reactivity of CS-45 toward singlet oxygen is much larger than that of the related compounds lacking the chroman ring.

Photodegradation and in vitro phototoxicity of the antidiabetic drug chlorpropamide.

Methanolic solutions of the phototoxic antidiabetic drug chlorpropamide (CAS 94-20-2, 1) are photolabile towards UVB light under aerobic conditions. Irradiation of 1 produces the formation of the stable compounds p-chlorobenzenesulfonamide (2), N-(p-chlorophenylsulfonyl)formamide (3) and the dimer 4. A radical intermediate was evidenced by thiobarbituric acid that was used as a radical sonde, as well as by the dimerization of cysteine. The compound 1 showed moderate lytic activity upon the photohemolysis in vitro test on human erythrocytes which was increased with the addition of traces of its aggregate excipient. Inhibition of this process on addition of reduced glutathione (GSH), superoxide dismutase (SOD) or ascorbic acid suggests the involvement of radicals and superoxide ion in the photohemolysis process. The absence of inhibition with 1,4-diazabicyclo[2.2.2]octane (DABCO) and sodium azide (NaN3), and the lack of formation of singlet oxygen during the photolysis (confirmed with 2,5-dimethylfuran) rule out the possibility of participation of 1O2 in this process. Glutathione depletion was also observed. No photohemolysis was detected in the presence of the isolated photoproduct.