Mechanism of 2-hydropropyl-beta-cyclodextrin in the stabilization of frozen formulations.

Freezing of commonly used parenteral products to increase pharmaceutical stability for cost-saving purposes is a common practice in patient care. However, frozen meropenem, a model drug, in saline has a shelf life of less than a month due to the low glass transition temperature (Tg'): below -40°C. When meropenem is formulated with the 2-hydroxypropyl-ß-cyclodextrin (HPBC) the shelf life (⩾90% potency) is extrapolated to be greater than one year at -25°C based on data for storage at 6months. The mechanisms that may explain meropenem-HPBC formulation frozen stability include vitrification and/or formation of an inclusion complex. Although NMR data indicated complexation of meropenem by HPBC in a ratio of 0.6:1, inclusion was unlikely to be the mechanism as stability was not extended to the thawed solutions. Therefore, vitrification is concluded to be the stabilization mechanism. The Tg' for meropenem-HPBC (13.3%) formulation at pH 7.9 was -17.75°C which was similar to that of a meropenem solution formulated with a known vitrifying agent, Dextran 40. This higher Tg' for HPBC was unexpected based on trends predicted by the Fox-Flory equation. Trial formulations containing either Dextran 1, Dextran 40, hydroxyethyl starch, or sulfobutyl-beta-cyclodextrin heptasodium (Captisol®) were also unable to stabilize meropenem as the Tg' values were below the frozen storage temperature. Upon 6-month storage, potency losses were -3.0% and -7.7% for meropenem frozen premix formulated in 13.3% HPBC (pH 7.9) at -25 and -20°C storage, respectively; versus -31.2% and -60.8% for controls. Frozen premixes with high ionic strength (containing NaCl or Captisol®) and/or at pH 7.3 were also found to be unstable.

NMR of heparin API: investigation of unidentified signals in the USP-specified range of 2.12-3.00 ppm.

This article addresses the identification and quantification of the chemical species resulting in resonances at 2.17 and 2.25 ppm in the (1)H nuclear magnetic resonance (NMR) spectrum of pharmaceutical-grade heparin sodium. The NMR signals in question were first confirmed to arise from chemical moieties covalently attached to the heparin molecule through NMR diffusion experiments as well as chemical treatment of heparin active pharmaceutical ingredient (API) containing the resonances. The material responsible for the extra NMR signals was then demonstrated by NMR spiking studies to be something other than oversulfated chondroitin sulfate and was finally identified as an O-acetylation product of heparin through (13)C labeling experiments with subsequent NMR analysis. The extent of O-acetylation was quantified using three orthogonal techniques: (1)H NMR, ion chromatography, and headspace gas chromatography/mass spectrometry. The results of this work showed good agreement between the three quantitative methods developed to analyze the signals in the United States Pharmacopeia-specified region of 2.12-3.00 ppm for heparin API.

Aerosol based detectors for the investigation of phospholipid hydrolysis in a pharmaceutical suspension formulation.

A high performance liquid chromatography (HPLC) method was developed to quantify free fatty acids (FFA) in a pharmaceutical suspension formulated with phospholipids as stabilizing agents. Specifically, a suspension of crystalline itraconazole microparticles stabilized with Lipoid E80 was used as a model system to study the physicochemical stability of an aqueous, phospholipid-based suspension for injection. The hydrolysis of the phospholipids during storage at elevated temperatures (40 degrees C) necessitated the development of a suitable HPLC method for the determination of free fatty acid content in the suspension samples. HPLC methods using two types of aerosol detectors were investigated for the above purpose. Reversed-phase separation coupled with either an evaporative light scattering detector (ELSD) or a Corona(Plus) charged aerosol detector (CAD) was used. A comparison of the methods indicated that the CAD method provided better sensitivity, precision, recovery, and linearity for the parameters evaluated. As a result, this method was chosen for the stability study of itraconazole suspension and has been incorporated in subsequent formulation studies.

Comparison of electrospray ionization mass spectrometry and evaporative light scattering detections for the determination of Poloxamer 188 in itraconazole injectable formulation.

A high performance liquid chromatography (HPLC) method for Poloxamer 188 using size-exclusion chromatography (SEC) was developed and two different detection mechanisms, evaporative light scattering (ELSD) and electrospray ionization mass spectrometry (ESI-MS), were compared for their quantification capabilities in itraconazole formulation. Both detection techniques coupled with SEC separation were highly effective for the determination of Poloxamer 188, which is difficult to analyze by other common HPLC methods. As expected, ESI-MS detection provided sensitivity and selectivity superior to ELSD. But since the analyte is an excipient in the formulation, high sensitivity was not required and ELSD's simplicity and ruggedness made it more appropriate for routine analysis of this formulation.

Determination of polysorbate 80 in parenteral formulations by high-performance liquid chromatography and evaporative light scattering detection.

Drugs that are not very soluble in aqueous formulations are solubilized with surfactants such as polysorbate 80. In order to evaluate the stability of excipient such as polysorbate 80 in drug formulation, a rapid chromatographic methodology is desired; however, polysorbate 80 does not have a strong chromophore for monitoring by absorption spectrometry. A simple and fast method for the analysis of polysorbate 80 in pharmaceutical formulations was developed using high-performance liquid chromatography with evaporative light scattering detection (ELSD). Separation of polysorbate 80 as a single peak was achieved on a C18 column using a methanol/water gradient mobile phase and ELS detection. The method is specific for polysorbate 80 in the formulation as there were no interferences from the drug or other excipients. Precision, recovery, linearity and limit of quantitation/detection experiments gave acceptable results during the evaluation of the method.