Characterization of a solid state reaction product from a lyophilized formulation of a cyclic heptapeptide. A novel example of an excipient-induced oxidation

Identification and structure elucidation of a new degradation impurity in the multi-component tablets of amlodipine besylate

New unknown impurity at m/z 421.15 was observed during the accelerated stability analysis (40 °C/75% relative humidity) in the multi-component tablets of amlodipine besylate by reversed-phase ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS). UHPLC-MS and nuclear magnetic resonance (NMR) techniques were employed to identify and fully characterize the degradation compound. The degradation product was unambiguously identified as 3-ethyl 5-methyl 4-(2-chlorophenyl)-6-methyl-2-(morpholin-2-yl)-1,4-dihydropyridine-3,5-dicarboxylate and mechanism of its formation was proposed. It was confirmed that the degradation product was formed by the reaction of amlodipine with formaldehyde originating from the excipients present in the dosage form.

Excipient Stability in Oral Solid Dosage Forms: A Review

The choice of excipients constitutes a major part of preformulation and formulation studies during the preparation of pharmaceutical dosage forms. The physical, mechanical, and chemical properties of excipients affect various formulation parameters, such as disintegration, dissolution, and shelf life, and significantly influence the final product. Therefore, several studies have been performed to evaluate the effect of drug-excipient interactions on the overall formulation. This article reviews the information available on the physical and chemical instabilities of excipients and their incompatibilities with the active pharmaceutical ingredient in solid oral dosage forms, during various drug-manufacturing processes. The impact of these interactions on the drug formulation process has been discussed in detail. Examples of various excipients used in solid oral dosage forms have been included to elaborate on different drug-excipient interactions.

Chemical degradation of proteins in the solid state with a focus on photochemical reactions

Protein pharmaceuticals comprise an increasing fraction of marketed products but the limited solution stability of proteins requires considerable research effort to prepare stable formulations. An alternative is solid formulation, as proteins in the solid state are thermodynamically less susceptible to degradation. Nevertheless, within the time of storage a large panel of kinetically controlled degradation reactions can occur such as, e.g., hydrolysis reactions, the formation of diketopiperazine, condensation and aggregation reactions. These mechanisms of degradation in protein solids are relatively well covered by the literature. Considerably less is known about oxidative and photochemical reactions of solid proteins. This review will provide an overview over photolytic and non-photolytic degradation reactions, and specially emphasize mechanistic details on how solid structure may affect the interaction of protein solids with light.

Alternative carriers in dry powder inhaler formulations

The aerosolization efficiency of a powder is highly dependent on carrier characteristics, such as particle size distribution, shape and surface properties. The main objective in the inhalation field is to achieve a high and reproducible pulmonary deposition. This can be provided by successful carrier selection and careful process optimization for carrier modification. Lactose is the most common and frequently used carrier in dry powder inhaler (DPI) formulations. But lactose shows some limitations in formulation with certain drugs and peptides that prohibit its usage as a carrier in DPI formulations. Here, we criticality review the most important alternative carriers to lactose with merits, demerits and applications in DPI formulations.

Reactive impurities in excipients: profiling, identification and mitigation of drug-excipient incompatibility

Reactive impurities in pharmaceutical excipients could cause drug product instability, leading to decreased product performance, loss in potency, and/or formation of potentially toxic degradants. The levels of reactive impurities in excipients may vary between lots and vendors. Screening of excipients for these impurities and a thorough understanding of their potential interaction with drug candidates during early formulation development ensure robust drug product development. In this review paper, excipient impurities are categorized into six major classes, including reducing sugars, aldehydes, peroxides, metals, nitrate/nitrite, and organic acids. The sources of generation, the analytical method for detection, the stability of impurities upon storage and processing, and the potential reactions with drug candidates of these impurities are reviewed. Specific examples of drug-excipient impurity interaction from internal research and literature are provided. Mitigation strategies and corrective measures are also discussed.

Identification of pharmaceutical impurities in formulated dosage forms

Structure elucidation of pharmaceutical impurities is an important part of the drug product development process. Impurities can have unwanted pharmacological or toxicological effects that seriously impact product quality and patient safety. This review focuses on current analytical strategies for chemical and structural identification of pharmaceutical impurities. Potential sources and mechanisms of impurity formation are discussed for both drug substance and drug product applications. The utility of liquid chromatography-mass spectrometry (LC/MS) for providing structure-rich information is highlighted throughout this review. Other hyphenated analytical techniques including LC/nuclear magnetic resonance, gas chromatography/MS, and size-exclusion chromatography/chemiluminescent nitrogen detectors are also discussed, as LC/MS alone sometimes cannot reveal or confirm the final structures as required during dosage form development.

Use of the Antioxidant BHT in Asymmetric Membrane Tablet Coatings to Stabilize the Core to the Acid Catalyzed Peroxide Oxidation of a Thioether Drug

The application of a controlled-release asymmetric membrane (AM) coating containing cellulose acetate and polyethylene glycol 3350 (PEG3350) to a stable osmotic tablet core resulted in the oxidative degradation of active ingredient located in the core. It was hypothesized that the production of hydroperoxides from PEG3350 in the coating was responsible for the electrophilic oxidation of drug to the sulfoxide degradation product. The type and solubility of carboxylic acid excipient used to formulate the drug release profile of the osmotic tablet significantly influenced the amount of oxidation. By adding the antioxidant butylated hydroxytoluene (BHT) to the coating, oxidation was significantly inhibited in tablets placed on accelerated stability. Of three additives that were used to prevent oxidation [BHT, ferrous sulfate, and ethylenediaminetetraacetic acid (EDTA)], BHT was shown to be the most effective at preventing sulfoxide formation. The BHT was also shown to be more effective in the coating rather than in the core due to its location closer to the source of the oxidizing species, PEG3350, in the coating.

High throughput screening of protein formulation stability: practical considerations

The formulation of protein drugs is a difficult and time-consuming process, mainly due to the complexity of protein structure and the very specific physical and chemical properties involved. Understanding protein degradation pathways is essential for the success of a biopharmaceutical drug. The present review concerns the application of high throughput screening techniques in protein formulation development. A protein high throughput formulation (HTF) platform is based on the use of microplates. Basically, the HTF platform consists of two parts: (i) sample preparation and (ii) sample analysis. Sample preparation involves automated systems for dispensing the drug and the formulation ingredients in both liquid and powder form. The sample analysis involves specific methods developed for each protein to investigate physical and chemical properties of the formulations in microplates. Examples are presented of the use of protein intrinsic fluorescence for the analysis of protein aqueous properties (e.g., conformation and aggregation). Different techniques suitable for HTF analysis are discussed and some of the issues concerning implementation are presented with reference to the use of microplates.

Characterization of the novel ophthalmic drug carrier Sophisen in two of its derivatives: 3A Ofteno and Modusik-A Ofteno

Sophisen, a new ophthalmic drug carrier, was characterized using physicochemical and morphological criteria. Diclofenac belongs to a nonsteroidal anti-inflammatory molecule group and its ophthalmic use avoids side effects produced by steroid drugs. Cyclosporine-A is a cyclic peptide used as an immunosuppressive when administrated systemically. Its application in ophthalmology has been reported, but it is a very poor soluble drug. Diclofenac sodium and Cyclosporine-A were mixed with Sophisen to render two new ophthalmic solutions that were named 3A Ofteno and Modusik-A Ofteno, respectively. Based on transmission electron microscopy and dynamic light scattering studies, we concluded that Sophisen is a polydisperse solution with a molecular weight of 413 +/-122 kDa, whereas 3A Ofteno and Modusik-A Ofteno are monodisperse solutions with molecular weights of 169 +/- 44 and 153 +/- 10, respectively. Sophisen was shown to be a good carrier for diclofenac sodium as evaluated by passive diffusion through the cornea. A comparative study suggests that diclofenac applied as eye drops was better tolerated when associated with Sophisen. In addition, Modusik-A Ofteno, a new aqueous solution of Cyclosporine-A, improved tear production in patients with moderate or severe dry eye condition.

Carrier-based strategies for targeting protein and peptide drugs to the lungs

With greater interest in delivery of protein and peptide-based drugs to the lungs for topical and systemic activity, a range of new devices and formulations are being investigated. While a great deal of recent research has focused on the development of novel devices, attention must now be paid to the formulation of these macromolecular drugs. The emphasis in this review will be on targeting of protein/peptide drugs by inhalation using carriers and ligands.

Studies on the reactions between daptomycin and glyceraldehyde

The objectives of this project were to determine the reaction pathways of daptomycin in the presence of glyceraldehyde in acidic solutions, and to quantitate the kinetics of the major pathways. In the presence of glyceraldehyde (pH range 1-7 at 25 to 60 degrees C), daptomycin formed two major products separable by RP-HPLC. The products were identified using UV spectroscopy, fluorimetry, mass spectrometry, and 2D-1H NMR. The reaction scheme involved the reversible formation of imine and anilide derivatives. Carbinolamine was believed to be a common intermediate in formation pathways of both products. The carbinolamine intermediate underwent either acid catalyzed dehydration resulting in imine formation or intramolecular hydrogen bonding and bond cleavage giving rise to anilide formation. In mild acid conditions, both products reversed to daptomycin. The reaction between daptomycin and glyceraldehyde was first-order with respect to both reactants. In a pH range of 1-7, the imine formation rate was pH dependent with a maximum rate at approximate pH values of 3-4. The observed pH dependence was consistent with the pH dependence of typical amine-aldehyde reactions.

Excipient-drug interactions in parenteral formulations

Excipients are added to parenteral formulations to enhance or maintain active ingredient solubility (solubilizers) and/or stability (buffers, antioxidants, chelating agents, cryo- and lyoprotectants). Excipients also are important in parenteral formulations to assure safety (antimicrobial preservatives), minimize pain and irritation upon injection (tonicity agents), and control or prolong drug delivery (polymers). These are all examples of positive or synergistic interactions between excipients and drugs. However, excipients may also produce negative effects such as loss of drug solubility, activity, and/or stability. This review article will highlight documented interactions, both synergistic and antagonistic, between excipients and drugs in parenteral formulations. The reader will gain better understanding and appreciation of the implications of adding formulation ingredients to parenteral drug products.

Stabilization of pharmaceuticals to oxidative degradation

A guide for stabilization of pharmaceuticals to oxidation is presented. Literature is presented with an attempt to be a ready source for data and recommendations for formulators. Liquid and solid dosage forms are discussed with options including formulation changes, additives, and packaging documented. In particular, selection of and methods for use of antioxidants are discussed including recommended levels.

Influence of peroxide impurities in povidone and crospovidone on the stability of raloxifene hydrochloride in tablets: identification and control of an oxidative degradation product

The purpose of this study was to identify a degradation product in a tablet formulation of raloxifene hydrochloride (R-HCl), delineate the role of excipients in its formation, and develop a rational strategy for its control. The degradant was identified as an N-oxide derivative of the drug substance based upon spectroscopic characterization and chromatographic comparison to the synthetic N-oxide. To identify the factors contributing to the formation of N-oxide, binary mixtures of each excipient with R-HCl were exposed to 125 degrees C in open containers. Raloxifene hydrochloride underwent an order of magnitude increase in conversion to the N-oxide in the presence of two excipients, povidone and crospovidone, as compared with its conversion in the presence of other excipients. To confirm a hypothesis that peroxide impurities in these two excipients contributed to the oxidation of the drug substance, tablet lots were spiked with quantities of H2O2 equivalent to 200, 400, 600, and 800 ppm peroxide over the intrinsic levels present in povidone and crospovidone. A strong correlation was observed between the total peroxide level and the quantity of the N-oxide formed upon accelerated storage. From these experiments a rational limit test for peroxide content in povidone and crospovidone was adopted as part of a control strategy to limit formation of the degradation product.

Solid-state chemical stability of proteins and peptides

Peptide and protein drugs are often formulated in the solid-state to provide stabilization during storage. However, reactions can occur in the solid-state, leading to degradation and inactivation of these agents. This review summarizes the major chemical reactions affecting proteins and peptides in the solid-state: deamidation, peptide bond cleavage, oxidation, the Maillard reaction, beta-elimination, and dimerization/aggregation. Physical and chemical factors influencing these reactions are also discussed. These include temperature, moisture content, excipients, and the physical state of the formulation (amorphous vs crystalline). The review is intended to serve as an aid for those involved in formulation, and to stimulate further research on the determinants of peptide and protein reactivity in the solid-state.