Development of an ion-pair reversed-phase HPLC method with indirect UV detection for determination of phosphates and phosphites as impurities in sodium risedronate.

A method based on RP-HPLC with indirect UV detection was developed for the determination of phosphates and phosphites as impurities in sodium risedronate. RP separation of the phosphates and phosphites was achieved by adding tetrabutylammonium hydroxide as an ion-pairing agent in the mobile phase. Potassium hydrogen phthalate was added to the mobile phase as an ionic chromophore in order to obtain high background absorption of the mobile phase. Separation was performed on a C18 column using a mixture of pH 8.2 buffer (containing 0.5 mM tetrabutylammonium hydroxide and 1 mM phthalate) and acetonitrile (95 + 5, v/v) as the mobile phase, with indirect UV detection at 248 nm. The validation of the method included determination of specificity/selectivity, linearity, LOD, LOQ, accuracy, precision, and robustness. The LOD was 0.86 microg/mL for phosphates and 0.76 microg/mL for phosphites. The LOQ was 2.60 microg/mL for phosphates and 2.29 microg/mL for phosphites. The developed method is suitable for quantitative determination of phosphates and phosphites as impurities in QC of sodium risedronate.

Importance of 6-Thioguanine Nucleotide Metabolite Monitoring in Inflammatory Bowel Disease Patients Treated with Azathioprine.

The active metabolite of azathioprine, 6-thioguanine nucleotide (6-TGN) is the main component responsible for the immunosuppressive effect in treatment of inflammatory bowel disease (IBD). The aim of this study was to assess the correlation between the concentration of 6-thioguanine nucleotide and disease activity, azathioprine-related adverse effects and time duration of treatment in patients with inflammatory bowel disease. Thirty-four patients were included in this study. Type of disease, gender, time duration of therapy and adverse effects were recorded. Metabolite concentration was determined by high performance liquid chromatography. Twenty-one percent of patients have experienced an adverse effect, with leucocytopenia most commonly occurring (42.9%). More adverse effects were registered when patients were treated with azathioprine in a period of less than 3 months in comparison to the group of patients that have been under therapy between 3-12 months and more than 12 months (p˂0.05). Most of the patients that presented any adverse effect had high 6-TGN concentration (>450 pmol/8x108 Er). The mean value of 6-TGN metabolite concentration in IBD patients treated with azathioprine was 437.46 pmol/8x108 Er ± 198.82 pmol/8x108. The time duration of azathioprine treatment did not have any significant impact on the achieved 6-TGN concentration (p>0.05).Twenty patients (58.9%) had achieved remission after therapy initiation with azathioprine. More alertness is recommended to clinicians towards patients in the first 3 months of the therapy. Our study demonstrated that higher 6-TGN concentration is associated with azathioprine toxicity.

Studying the formation of aggregates in recombinant human granulocyte-colony stimulating factor (rHuG-CSF), lenograstim, using size-exclusion chromatography and SDS-PAGE.

The stability of proteins is a subject of intense current interest. Aggregation, as a dominant degradation pathway for therapeutic proteins, may cause multiple adverse effects, including loss of efficacy and immunogenicity. In the present study, the formation of aggregates in lenograstim under physiological conditions was monitored. For this purpose, a simple and selective size-exclusion high-performance liquid chromatography method for detection and separation of aggregates from intact protein was developed. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis was performed under reducing and non-reducing conditions to determine the nature of aggregate bond formation. Using both techniques, the presence of a low aggregate content attached via disulfide bonds was detected.

Formulation and evaluation of diazepam hydrogel for rectal administration.

Diazepam (DZP) has become a commonly used drug for treatment of acute repetitive epileptic seizures and febrile convulsions in children. Considering the advantages of rectal administration of DZP, the objective of our study was to formulate and evaluate rectal hydrogels containing DZP as a drug substance in combination with suitable co-solvents and preservatives. Prepared HPMC (hydroxypropyl methylcellulose) hydrogels containing different concentrations of DZP (2, 4 and 6 mg mL(-1)) manifested good quality in respect to physico-chemical parameters (pH value, drug content, ingredients content and viscosity), antimicrobial efficiency and microbiological quality. Under the proposed HPLC conditions, satisfactory separation of DZP and the preservatives used was achieved. In vitro release studies have shown that the total amount of DZP was released in a period of 3 h. Prepared formulations were stable for four months at 26 degrees C (ambient temperature characteristic of the 2nd climate zone).