Application of surface area measurement for identifying the source of batch-to-batch variation in processability.

The primary goal of this study was to evaluate the use of specific surface area as a measurable physical property of materials for understanding the batch-to-batch variation in the flow behavior. The specific surface area measurements provide information about the nature of the surface making up the solid, which may include defects or void space on the surface. These void spaces are often present in the crystalline material due to varying degrees of disorderness and can be considered as amorphous regions. In the present work, the specific surface area for 10 batches of the same active pharmaceutical ingredient (compound 1) with varying quantity of amorphous content was investigated. Some of these batches showed different flow behavior when processed using roller compaction. The surface area value was found to increase in the presence of low amorphous content, and decrease with high amorphous content as compared to crystalline material. To complement the information obtained from the above study, physical blends of another crystalline active pharmaceutical ingredient (compound 2) and its amorphous form were prepared in known proportions. Similar trend in specific surface area value was found. Tablets prepared from known formulation with varying amorphous content of the active ingredient (compound 3) also exhibited the same trend. A hypothesis to explain the correlation between the amorphous content and specific surface area has been proposed. The results strongly support the use of specific surface area as a measurable tool for investigation of source of batch to batch variation in processability.

Comprehensive validation scheme for in situ fiber optics dissolution method for pharmaceutical drug product testing.

There has been a growing interest during the past decade in the use of fiber optics dissolution testing. Use of this novel technology is mainly confined to research and development laboratories. It has not yet emerged as a tool for end product release testing despite its ability to generate in situ results and efficiency improvement. One potential reason may be the lack of clear validation guidelines that can be applied for the assessment of suitability of fiber optics. This article describes a comprehensive validation scheme and development of a reliable, robust, reproducible and cost-effective dissolution test using fiber optics technology. The test was successfully applied for characterizing the dissolution behavior of a 40-mg immediate-release tablet dosage form that is under development at Novartis Pharmaceuticals, East Hanover, New Jersey. The method was validated for the following parameters: linearity, precision, accuracy, specificity, and robustness. In particular, robustness was evaluated in terms of probe sampling depth and probe orientation. The in situ fiber optic method was found to be comparable to the existing manual sampling dissolution method. Finally, the fiber optic dissolution test was successfully performed by different operators on different days, to further enhance the validity of the method. The results demonstrate that the fiber optics technology can be successfully validated for end product dissolution/release testing.

Content uniformity determination of pharmaceutical tablets using five near-infrared reflectance spectrometers: a process analytical technology (PAT) approach using robust multivariate calibration transfer algorithms.

Near-infrared calibration models were developed for the determination of content uniformity of pharmaceutical tablets containing 29.4% drug load for two dosage strengths (X and Y). Both dosage strengths have a circular geometry and the only difference is the size and weight. Strength X samples weigh approximately 425 mg with a diameter of 12 mm while strength Y samples, weigh approximately 1700 mg with a diameter of 20mm. Data used in this study were acquired from five NIR instruments manufactured by two different vendors. One of these spectrometers is a dispersive-based NIR system while the other four were Fourier transform (FT) based. The transferability of the optimized partial least-squares (PLS) calibration models developed on the primary instrument (A) located in a research facility was evaluated using spectral data acquired from secondary instruments B, C, D and E. Instruments B and E were located in the same research facility as spectrometer A while instruments C and D were located in a production facility 35 miles away. The same set of tablet samples were used to acquire spectral data from all instruments. This scenario mimics the conventional pharmaceutical technology transfer from research and development to production. Direct cross-instrument prediction without standardization was performed between the primary and each secondary instrument to evaluate the robustness of the primary instrument calibration model. For the strength Y samples, this approach was successful for data acquired on instruments B, C, and D producing root mean square error of prediction (RMSEP) of 1.05, 1.05, and 1.22%, respectively. However for instrument E data, this approach was not successful producing an RMSEP value of 3.40%. A similar deterioration was observed for the strength X samples, with RMSEP values of 2.78, 5.54, 3.40, and 5.78% corresponding to spectral data acquired on instruments B, C, D, and E, respectively. To minimize the effect of instrument variability, calibration transfer techniques such as piecewise direct standardization (PDS) and wavelet hybrid direct standardization (WHDS) were used. The PDS approach, the RMSEP values for strength X samples were lowered to 1.22, 1.12, 1.19, and 1.08% for instruments B, C, D, and E, respectively. Similar improvements were obtained using the WHDS approach with RMSEP values of 1.36, 1.42, 1.36, and 0.98% corresponding to instruments B, C, D, and E, respectively.

Strategy for identification of leachables in packaged pharmaceutical liquid formulations.

Drug stability is one of the key properties to be monitored in pharmaceutical drug development. Drug degradation products, impurities and/or leachables from the drug product and packages may have significant impacts on drug efficacy, safety profile and storage conditions. In the registration stability samples of an ophthalmic pharmaceutical drug product, an unknown compound was found at a level of 0.19% by HPLC analysis. Subsequent liquid chromatography/mass spectrometry (LC/MS) analysis with electrospray ionization (ESI) indicated that the unknown was not related to the drug substance and was most likely a leachable. Identification of this unknown leachable was needed to evaluate the impact on drug safety. Through systematic extraction of various components or component combination of the packaging materials, and subsequently LC/MS analysis, the unknown was found to be a leachable coming from the varnish applied to the label. In general, using LC/MS alone is not sufficient to elucidate the structure of a complete unknown. Gas chromatography/mass spectrometry (GC/MS) was then conducted with a chemical ionization (CI) source to determine the retention time and mass of the compound of interest. Both CI and ESI sources generated the same protonated molecular ion [M+H] and similar fragmentation ions, which provides a good correlation of the unknown eluted in the liquid chromatogram and in the gas chromatogram. GC/MS with electron impact (EI) was then conducted to obtain the EI mass spectrum of this unknown. It was identified as monomethyl derivative of mephenesin through the NIST library search. The identification strategy utilized electrospray LC/MS and GC/MS with chemical and electron ionization sources which provided complimentary information for structure elucidation of this unknown compound. This combination approach in conjunction with systematic extraction was necessary for the determination of the source of this unknown in the pharmaceutical drug stability studies.

The use of LC/MS, GC/MS, and LC/NMR hyphenated techniques to identify a drug degradation product in pharmaceutical development.

Understanding drug degradation in the formulated product is critical in pharmaceutical development as it has significant impacts on drug efficacy, safety profile and storage conditions. As a result, identification of degradation compounds has taken an important role in the drug development process. In this study, various hyphenated analytical techniques, such as liquid chromatography mass spectrometry (LC/MS), gas chromatography mass spectrometry (GC/MS), and liquid chromatography nuclear magnetic resonance with a solid phase extraction interface (LC/SPE/NMR), have been applied to the identification of a drug degradation product which grew over time in the stability study of the drug product. The target unknown is less polar and more unsaturated than the drug substance based upon reverse phase HPLC relative retention time and UV spectra. It is not ionizable by electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) in either a positive or a negative mode. The unknown was isolated by an HPLC fraction collector and enriched by solid phase extraction. GC/MS with chemical ionization (CI) was employed to determine the molecular weight of this compound. Its fragmentation pattern was determined by CI-MS/MS using an ion trap mass spectrometer. The isolated material was also analyzed by LC/SPE/NMR, from which the structure of this compound was further characterized. The study utilizes a combination of various hyphenated analytical techniques to obtain complimentary information for structure elucidation of the unknown. The combination approach is critical for unambiguous impurity structure elucidation in drug degradation studies of pharmaceutical drug products.