Time-Gated Raman Spectroscopy for Quantitative Determination of Solid-State Forms of Fluorescent Pharmaceuticals.

Raman spectroscopy is widely used for quantitative pharmaceutical analysis, but a common obstacle to its use is sample fluorescence masking the Raman signal. Time-gating provides an instrument-based method for rejecting fluorescence through temporal resolution of the spectral signal and allows Raman spectra of fluorescent materials to be obtained. An additional practical advantage is that analysis is possible in ambient lighting. This study assesses the efficacy of time-gated Raman spectroscopy for the quantitative measurement of fluorescent pharmaceuticals. Time-gated Raman spectroscopy with a 128 × (2) × 4 CMOS SPAD detector was applied for quantitative analysis of ternary mixtures of solid-state forms of the model drug, piroxicam (PRX). Partial least-squares (PLS) regression allowed quantification, with Raman-active time domain selection (based on visual inspection) improving performance. Model performance was further improved by using kernel-based regularized least-squares (RLS) regression with greedy feature selection in which the data use in both the Raman shift and time dimensions was statistically optimized. Overall, time-gated Raman spectroscopy, especially with optimized data analysis in both the spectral and time dimensions, shows potential for sensitive and relatively routine quantitative analysis of photoluminescent pharmaceuticals during drug development and manufacturing.

Physical Stability of Freeze-Dried Isomalt Diastereomer Mixtures.

PURPOSE: Isomalt is a sugar alcohol used as an excipient in commercially available solid oral dosage forms. The potential of isomalt as a novel freeze-drying excipient was studied in order to increase knowledge of the behavior of isomalt when it is freeze-dried. METHODS: Isomalt was freeze-dried in four different diastereomer compositions and its physical stability was investigated with differential scanning calorimetry, Fourier-transform infrared and Raman spectroscopy, X-ray powder diffraction, Karl-Fischer titration and thermogravimetric analysis in order to verify the solid state form of isomalt after freeze-drying and observe any changes occurring during storage in three different relative humidity conditions. RESULTS: Isomalt was successfully transformed into the amorphous form with freeze-drying and three diastereomer combinations remained stable as amorphous during storage; one of the diastereomer compositions showed signs of physical instability when stored in the highest relative humidity condition. The four different crystalline diastereomer mixtures showed specific identifiable solid state properties. CONCLUSIONS: Isomalt was shown to be a suitable excipient for freeze-drying. Preferably a mixture of the diastereomers should be used, as the mixture containing only one of the isomers showed physical instability. A mixture containing a 1:1 ratio of the two diastereomers showed the best physical stability in the amorphous form.

The use of disaccharides in inhibiting enzymatic activity loss and secondary structure changes in freeze-dried ß-galactosidase during storage.

PURPOSE: The purpose of this study is to show how disaccharides differ in their ability to protect lyophilized ß-galactosidase from enzymatic activity loss and secondary structure changes during storage. METHODS: ß-galactosidase was lyophilized with trehalose, sucrose, cellobiose or melibiose at 2:1, 20:1 and 40:1 excipient/protein weight ratios, and stored up to 90 days at 45 °C. Protein enzymatic activity was studied using o-nitrophenyl-ß-D-galactopyranoside cleavage test, and its secondary structure in lyophilizates analyzed using Fourier transform infrared spectroscopy. The crystallization tendencies, glass transition temperatures and water contents of lyophilizates were evaluated using x-ray powder diffractometry, differential scanning calorimetry and thermogravimetry, respectively. RESULTS: The enzymatic activity of ß-galactosidase decreased more slowly in lyophilizates containing trehalose or melibiose at 2:1 excipient/protein weight ratio when compared to those containing sucrose or cellobiose. Similar behavior was observed when analyzing the protein's secondary structure in lyophilizates. In 20:1 and 40:1 excipient/protein weight ratio lyophilizates the decrease of enzymatic activity was less dependent on the excipient, but activity was always amongst the highest in melibiose lyophilizates. CONCLUSIONS: Melibiose was shown to be effective in protecting lyophilized ß-galactosidase during storage. The protein secondary structure was shown to change at comparable rate in lyophilizates as its enzymatic activity after rehydration.

The Use of Video Instructions in Patient Education Promoting Correct Technique for Dry Powder Inhalers: An Investigation on Inhaler-Naïve Individuals.

Introduction: The correct use of a prescribed inhaler device is crucial for achieving successful disease management in asthma. This study investigates non-verbal, demonstrational videos as a method of teaching inhaler naïve individuals how to use a dry powder inhaler (DPI). Methods: Video instructions for four DPIs were examined using a mixed methodology; 31 inhaler-naïve individuals participated in the study. Participants were each shown a demonstrational video of one the four inhalers, after each video the participant demonstrated how they would use the inhaler. After demonstrating the use, participants crossed over to the next inhaler. The demonstrations were videotaped. A common questionnaire was filled at the beginning of the study and four inhaler-specific questionnaires which were filled out by the participant after each inhaler demonstration. Results: The frequency of participant error varied between inhalers. When asked about how they perceived the video instructions, participants often stated they would have liked to receive feedback on their performance. The importance of feedback was further highlighted by the fact that participants tended to overestimate their own inhaler technique. Conclusion: Non-verbal videos may be more efficient for some DPIs than for others as a method for providing inhaler instructions. Lack of feedback on the participants' inhaler performance emerged as a clear shortcoming of this educational method. Some steps in the inhalation process may be harder for individuals to remember and therefore require extra emphasis in order to achieve correct inhaler technique.

Isomalt and its diastereomer mixtures as stabilizing excipients with freeze-dried lactate dehydrogenase.

The purpose of this research was to study isomalt as a protein-stabilizing excipient with lactate dehydrogenase (LDH) during freeze-drying and subsequent storage and compare it to sucrose, a standard freeze-drying excipient. Four different diastereomer mixtures of isomalt were studied. The stability of the protein was studied with a spectrophotometric enzyme activity test and circular dichroism after freeze-drying and after 21 days of storage at 16% RH. Physical stability was analyzed with differential scanning calorimetry and Karl Fischer titration. Statistical analysis was utilized in result analysis. LDH activity was almost completely retained after freeze-drying with sucrose; whereas samples stabilized with isomalt diastereomer mixtures had a considerably lower protein activity. During storage the sucrose-containing samples lost most of their enzymatic activity, while the isomalt mixtures retained the protein activity better. In all cases changes to protein secondary structure were observed. Isomalt diastereomer mixtures have some potential as protein-stabilizing excipients during freeze-drying and subsequent storage. Isomalt stabilized LDH moderately during freeze-drying; however it performed better during storage. Future studies with other proteins are required to evaluate more generally whether isomalt would be a suitable excipient for pharmaceutical freeze-dried protein formulations.

The effect of mechanical dry coating with magnesium stearate on flowability and compactibility of plastically deforming microcrystalline cellulose powders.

Mechanofusion is a dry coating method that can be used to improve the flowability of cohesive powder by coating host particles with a lubricant, for example magnesium stearate (MgSt). It has been shown previously that fragmenting material can under some circumstances be mechanofused with MgSt without impairing compactibility of the powder and without reducing the dissolution rate of the resulting tablets. However, the effects on material with viscoelastic behaviour, known to be sensitive for the negative effects of MgSt, is not known. Therefore, mechanofusion of microcrystalline cellulose (MCC) with MgSt was investigated in this study. Four MCC grades were mechanofused with different MgSt concentrations and process parameters, and the resulting flowability and compactibility were studied. Starting materials and low-shear blended binary mixtures were studied as a reference. Mechanofusion improved the flow properties of small particle size MCC powders (d50 < 78 µm) substantially, but increasing the MgSt content consequently resulted in weaker tablets. Larger particle size MCC grades, however, fractured under the shear forces during the mechanofusion process and hence their flow properties were decreased. Improvement of the flow properties but also the negative effects on compactibility of small particle size grades were observed even at relatively mild mechanofusion parameters and low lubricant concentrations.

Characterisation of blends of paracetamol and citric acid.

The purpose of this study was to characterise physically stable amorphous blends that were sticky (low glass transition temperature) in ambient conditions. The effects of composition, melting time and melting temperature were evaluated with respect to physical and chemical property. Citric acid anhydrate and paracetamol were melt-quenched as binary mixtures and as pure materials. Bulk samples were characterised by differential scanning calorimetry, X-ray powder diffractometry, and Raman and Fourier transform infrared spectroscopy. The composition and the sample exposure to moisture affected significantly the physical stability of samples. The extreme melting conditions, coupled with long exposure to heat and a high melting temperature, lowered the overall crystallisation rate. Paracetamol had a stronger tendency to crystallise from the blends than did citric acid. The 50:50% (w/w) blend was physically stable for at least 27 weeks in dry conditions and was partly crystalline after 4 weeks of storage at a relative humidity of 43%. The result of the physical stability of blends is discussed in terms of hydrogen bonding interaction between paracetamol and citric acid and in relation to degradation products formed in a mixing state.

Challenge of paediatric compounding to solid dosage forms sachets and hard capsules - Finnish perspective.

OBJECTIVES: The study evaluated the quality of compounded sachets and hard gelatine capsules and their feasibility in paediatric drug administration. METHODS: Commercial tablets were compounded to sachets and capsules in hospital environment, and the uniformity of content and simulated drug dose were determined. KEY FINDINGS: Compounded formulations were successfully obtained for a range of drug substances; dipyridamole, spironolactone, warfarin and sotalol formulations were within acceptable limits for uniformity of content, in most cases. However, some loss of drug was seen. The type and amount of excipients were found to affect uniformity of content; good conformity of capsules was obtained using lactose monohydrate as filler, whereas microcrystalline cellulose was a better choice in sachets. In capsules, content uniformity was obtained for a range of drug doses. If the drug is aimed to be administered through a nasogastric tube, solubility of the drug and excipients should be considered, as they were found to affect the simulated drug dose in administration. CONCLUSIONS: Compounded sachets and capsules fulfilled the quality requirements in most cases. In compounding, the choice of excipients should be considered as they can affect conformity of the dosage form or its usability in practice. Quality assurance of compounded formulations should be taken into consideration in hospital pharmacies.

Stability of rituximab in freeze-dried formulations containing trehalose or melibiose under different relative humidity atmospheres.

The objective of the study was to compare the effectiveness of trehalose with that of melibiose in protecting a monoclonal antibody (rituximab) from aggregation, fragmentation, and secondary structure alterations during processing and subsequent storage. Because reducing disaccharides such as melibiose participate in Maillard reaction with proteins, especially in the presence of water, the lyophilizates were stored under different relative humidity (RH 5%, 11%, and 23%) atmospheres. Freeze drying was shown to cause clear alterations in rituximab secondary structure, an increase in noncovalent protein aggregation, and in some cases fragmentation. However, these changes were less pronounced in the formulation containing melibiose. Storing the lyophilizates under low RH (5%) proved to be most harmful to the stability of rituximab, intensifying secondary structure alterations and increasing protein aggregate content. Again, these changes were less aggravated in the formulation containing melibiose. Surprisingly, the concentration of aggregates larger than 1 µm decreased in some cases during storage at RH 11% and 23%. There was no indication that storage even under the highest RH (23%) would have caused significant amounts of Maillard reaction end products to be formed during 3 months of storage.

The effect of relative humidity on the physical properties of two melibiose monohydrate batches with differing particle size distributions and surface properties.

Melibiose monohydrate has shown promise when employed as a pharmaceutical excipient, but its physical properties have not been adequately characterized. Therefore, two different melibiose monohydrate batches were analyzed as received or after storage under different relative humidity (RH) atmospheres. The particle size distributions and specific surface areas of the two batches were shown to differ considerably, which also had an effect on their water sorption tendencies and on the intermolecular structure of melibiose after storage. The relatively large primary particles that were more abundant in one of the batches were shown to possess a porous surface structure, and water evaporation from them occurred in two phases when heated. Furthermore, storing the batch with smaller mean particle size under dry conditions affected the crystal structure and molecular vibrations of the sample more than in the case of the batch with larger mean particle size. It was concluded that the physical properties of melibiose monohydrate after storage at different RH atmospheres is largely governed by the primary particle size and porosity.