Application of hydroxypropyl methylcellulose as a protective agent against magnesium stearate induced crystallization of amorphous itraconazole

Itraconazole is a fungicide drug which has low bioavailability due to its poor water solubility. Amorphous solid dispersion (ASD) is a tool that has the potential to greatly increase the dissolution rate and extent of compounds. In this work, the dissolution of tablets containing the ASD of itraconazole with either hydroxypropyl methylcellulose (HPMC) or vinylpyrrolidone-vinyl acetate copolymer (PVPVA) was compared in order to find a formulation which can prevent the drug from the precipitation caused by magnesium stearate. Formulations containing the PVPVA-based ASD with HPMC included in various forms could reach 90% dissolution in 2 h, while HPMC-based ASDs could release 100% of the drug. However, HPMC-based ASD had remarkably poor grindability and low bulk density, which limited its processability and applicability. The latter issue could be resolved by roller compacting the ASD, which significantly increases the bulk density and the flowability of the powder blends used for tableting. This roller compaction step might be a base for the industrial application of HPMC-based, electrospun ASDs.

Investigation of Deteriorated Dissolution of Amorphous Itraconazole: Description of Incompatibility with Magnesium Stearate and Possible Solutions

Disadvantageous crystallization phenomenon of amorphous itraconazole (ITR) occurring in the course of dissolution process was investigated in this work. A perfectly amorphous form (solid dispersion) of the drug was generated by the electroblowing method (with vinylpyrrolidone-vinyl acetate copolymer), and the obtained fibers were formulated into tablets. Incomplete dissolution of the tablets was noticed under the circumstances of the standard dissolution test, after which a precipitated material could be filtered. The filtrate consisted of ITR and stearic acid since no magnesium content was detectable in it. In parallel with dissolution, ITR forms an insoluble associate, stabilized by hydrogen bonding, with stearic acid deriving from magnesium stearate. This is why dissolution curves do not have the plateaus at 100%. Two ways are viable to tackle this issue: change the lubricant (with sodium stearyl fumarate >95% dissolution can be accomplished) or alter the polymer in the solid dispersion to a type being able to form hydrogen bonds with ITR (e.g., hydroxypropyl methylcellulose). This work draws attention to one possible phenomenon that can lead to a deterioration of originally good dissolution of an amorphous solid dispersion.

Effective dose of miners due to natural radioactivity in a manganese mine in Hungary

In this study, short-term radon (RnDP) and thoron (TnDP) progeny measurements and dose estimation were carried out in winter and summer in a manganese mine, Hungary. Gamma-ray dose rate originating from external sources and (222)Rn and (226)Ra contents of spring-water from a mine was also measured. During working hours RnDP and TnDP concentration values changed between 12.1-175 and 0.14-0.42 Bq m(-3), respectively. The (222)Rn and (226)Ra concentration values in the karst spring-water were ∼6 Bq dm(-3) and 16 mBq dm(-3), respectively. The radiation dose resulting from the consumption of karst spring-water was negligible. The doses from the inhalation of TnDP and external gamma radiation were of the same magnitude, ∼0.1 mSv y(-1), which was rather negligible related to the estimated radiation dose of 5 mSv y(-1) from RnDP.

Evaluation and clinical application of a new method for measuring activity of von Willebrand factor-cleaving metalloprotease (ADAMTS13)

Thrombotic thrombocytopenic purpura (TTP) is associated with acquired or congenital deficiency of a plasma von Willebrand factor-cleaving protease (VWFcp). Based on partial amino acid sequence and genome-wide linkage analysis of pedigrees with congenital TTP, VWFcp was recently identified as a new member of the ADAMTS family and designated ADAMTS13. We developed a new, rapid, and simple method for measuring VWFcp activity based on the positive correlation between VWF multimeric size and Ristocetin cofactor activity (VWF:RCo). After dilution of plasma with low ionic Tris buffer and activation of the protease with barium chloride, a VWF concentrate is digested in the presence of urea. Subsequently, the residual VWF:RCo of the samples is assessed and used to calculate the VWFcp activity of the samples. The accuracy of the new technique is verified by estimating VWFcp activity for 282 plasma samples with the RCo-based assay and the original immunoblotting assay. The method is reproducible as shown by low intra- and interassay coefficients of variation (2.8% and 7.5% for normal samples, respectively, and 8.7% and 12.9% for abnormal samples, respectively). Furthermore, the clinical application of the new method is illustrated by measuring VWFcp of 14 patients with 22 episodes of acute TTP as well as other thrombotic, thrombocytopenic, or hemolytic disorders. Severe VWFcp deficiency was restricted to patients with acute, classic TTP. The majority of patients with low titer inhibitor respond to plasma exchange treatment with increase of VWFcp activity, whereas VWFcp deficiency persists in some patients with high titer inhibitor despite clinical remission.

High doses of methylene blue/light treatment crosslink the A-alpha-subunit of fibrinogen: influence of this photooxidization on fibrinogen binding to platelets

Irradiation in the presence of 1 microM methylene blue (MB) inactivates enveloped viruses in human plasma. This method is a useful tool to enhance the safety of human fresh-frozen plasma in blood donor banks. Via a photooxidative mechanism, viral structures as well as plasma proteins, especially fibrinogen, can be damaged. We investigated the effect of MB/light-induced photooxidative modification on the structure of fibrinogen and its function in the interaction with platelets in the concentration range of 150 microM MB. Densitometric scanning of reduced SDS-PAGE showed a decrease in the Aalpha-subunit of fibrinogen as well as an increase in high-molecular-weight (HMW) aggregates with increasing MB concentrations. The HMW aggregates may be due to covalent crosslinking of single Aalpha-subunits via photooxidation induced by MB/light treatment. Fibrinogen treated with high doses of MB (50 microM) showed a weaker binding to the fibrinogen receptor (GP IIb/IIIa) on the platelet surface and a decrease in platelet aggregation after stimulation with ADP and photooxidized fibrinogen. These effects were not detected in fibrinogen isolated from virus-inactivated plasma (1 microM MB). This was in agreement with normal binding of fibrinogen to GP IIb/IIIa on platelets.

The Thrombostat 4000. A sensitive screening test for von Willebrand's disease

The determination of the bleeding time (BT) is an essential diagnostic tool for von Willebrand's disease (vWD). However, the standardized Simplate BT still displays many variables and disadvantages. The present study reports on the sensitivity of the in vitro bleeding test (IVBT) in 51 vWD cases of different types and severity in comparison to the Simplate BT, and the correlation of both to each other as well as to von Willebrand factor (vWF:RCo) activity. The IVBT was performed in two modifications (2 mmol/L CaCl2 and 4 mmol/L ADP) on the Thrombostat 4000. The IVBT, particularly with CaCl2, showed clearly higher sensitivity than the BT (CaCl2: 84.3%, ADP: 61.7%, CaCl2 + ADP: 86.3, BT: 52.9%). The BT even failed in one patient with severe (type 2B) and in three with moderate vWD. The IVBT only failed in very mild forms of the disease (vW-F:RCo > 25%). In addition, the IVBT with ADP showed a close correlation to the vWF:RCo activity (r2 = 0.73). The significantly lower correlation of the BT with vWF:RCo (r2 = 0.49) was particularly due to the poor results in vWD of type 2 (type 2:r2 = 0.29; types 1 and 3:r2 = 0.61). Finally, BT and IVBT-ADP correlated with each other (r2 = 0.53), a rather good correlation considering that both are complex functional tests. It can be concluded from our study that the IVBT not only may replace the BT for most applications, but is clearly superior to BT for the screening (IVBT-CaCl2) and control of therapy in vWD.

Experience with Haemate P in von Willebrand's disease in adults

The virally inactivated pasteurized FVIII concentrate Haemate P contains nearly intact vWF multimers. It is currently the treatment of choice to achieve satisfactory hemostasis for moderate to severe vWD and for patients with variants of vWD that cannot be adequately treated with DDAVP or for whom DDAVP is contraindicated. Therefore, we treated patients with type Ia, type IIa, type IIb and type III vWD with Haemate P. A correction of the hemostatic defect was seen in all patients. The type of bleeding events included 24 gastrointestinal, 18 other mucosal, 5 central nervous system, 15 orthopedic and 4 other. 28 dental surgical procedures, 9 operative deliveries, 5 tonsillectomies, 17 orthopedic and 11 miscellaneous surgeries were performed under the cover of Haemate P.