An Evaluation of Wet Granulation Process Selection for API Prone to Polymorphic Form Conversion in the Presence of Moisture and Heat.

PURPOSE: Wet granulation (WG) is one of the most versatile processes to improve blend properties for processing. However, due to its need for moisture and heat, it is often considered not amenable to active pharmaceutical ingredients (APIs) prone to forming hydrates. Despite this claim, little literature exists evaluating the extent to which polymorphic form conversions occur for such API when processed with WG. This work sets out to explore two common WG methods, high-shear (HSG) and fluid-bed (FBG), and two drying processes, tray-drying (TD) and fluid-bed drying (FBD), and evaluate the risk they pose to hydrate form conversion. METHODS: The progression of anhydrous to hydrate form conversion of two model compounds with vastly different solubilities, fexofenadine hydrochloride and carbamazepine, was monitored throughout the various processes using powder X-ray diffraction. The resultant granules were characterized using thermogravimetric analysis, differential scanning calorimetry, BET adsorption, and sieve analysis. RESULTS: FBG and FBD processing resulted in the preservation of the original form of both APIs, while HSG+TD resulted in the complete conversion of the API. The FBD of fexofenadine and carbamazepine granules prepared with HSG resulted in partial and complete re-conversion back to the original anhydrous forms, respectively. CONCLUSION: The drying process is a critical factor in anhydrous form conservation. FBG and FBD yielded better preservation of the initial anhydrous forms. HSG could be an acceptable granulation method for API susceptible to hydrate formation if the API solubility is low. Selecting an FBG+FBD process minimizes API hydrate formation and preserves the original anhydrous form.

Effect of coating excipients on chemical stability of active coated tablets.

The objective of this study was to understand the impact of coating excipients on the chemical stability of active pan coated peliglitazar, which was prone to acid as well as base-catalyzed degradation. Four different coating formulations containing either polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose (HPMC) as a coating polymer and triacetin (glycerol triacetate) or polyethylene glycol (PEG) as a plasticizer/detackifier were used for coating of peliglitazar in a perforated pan coater. Tablets of one-milligram strength were manufactured by suspending the drug in the coating suspension and spray coating onto inert core tablets. The active coated tablets were placed on stability (40 °C/75% RH) in high-density polyethylene (HDPE) bottles in closed condition with desiccants or in open condition. Tablet samples were withdrawn and analyzed for degradants using a stability-indicating HPLC method. The overall stability for the film-forming polymer-plasticizer/detackifier combination showed the rank order: HPMC-triacetin > PVA-triacetin > HPMC-PEG > PVA-PEG. Higher stability of triacetin systems over PEG systems was attributed to lower solubility of peliglitazar in triacetin coating systems. For the same plasticizer/detackifier, higher stability of HPMC over PVA-based formulations was attributed to lower solubility and mobility of peliglitazar in HPMC compared with the PVA-based coating.

To Maintain Formulation Composition Similarity of Coated Tablets of Different Strengths: Should Coating be Based on Core Tablet Weight or Surface Area?

PURPOSE: As per the Japanese or SUPAC guidance to maintain formulation composition similarity across tablet strengths, the coating should be applied based on the core tablet surface area or weight, respectively. These two coating approaches were compared by evaluating protective effects of coating on the light stability of three model compounds. METHODS: Core tablets of three light sensitive drugs, nifedipine, rosuvastatin calcium, and montelukast sodium were coated either with PVA-based Opadry® II white or Opadry® II beige. The coated tablets were exposed to light up to three ICH cycles. RESULTS: For Opadry® II white, the surface area based coating provided consistent light protection across tablet strengths when the coating amount was more than 0.1 mg/mm2 compared to that based on core tablet weights. For Opadry® II beige, both approaches gave comparable and better light protection due to presence of iron oxides. The light protection by Opadry® II white could be because of physical barrier of coating, which was uniform across the strengths when it was based on core tablet surface area. CONCLUSION: For a routine tablet formulation development with Opadry color coating, it does not matter whether the coating is applied based on the core tablet surface area or weight.

Quality by design (QbD) approach to match tablet glossiness.

A quality by design (QbD) approach was used for a polyvinyl alcohol (PVA)-based coating to develop a 'look-alike' placebo tablet, which can match the glossiness (shine) of an innovator tablet. Critical coating parameters such as exhaust temperature, drying capacity, solid concentration in coating dispersion, and plasticizer concentration were studied using a full factorial design of experiment (DoE). Total of 20 experimental coating runs was executed on a pilot scale using a perforated pan coater. Coated tablets were evaluated visually against the innovator product by a panel of 13 volunteers using an individual questionnaire about the tablet appearance. The tablet appearance included factors such as tablet surface shine, surface roughness, and logo bridging. These data were analyzed using JMP software. Solid concentration in coating dispersion and drying capacity were found to be the key contributing parameters for tablet surface shine. Human observations were more discerning in spotting subtle differences in tablet appearance than Munsell evaluation. By the judicious selection of a solid concentration in coating dispersion and drying conditions, a look-alike placebo tablet was successfully developed. Change in tablet shape or size did not affect the tablet shine. However, replacement of PVA-based coating with hydroxypropyl methylcellulose (HPMC)-based coating resulted in reduced shine irrespective of tablet shape and size.

"Development of Fixed Dose Combination Products" Workshop Report: Considerations of Gastrointestinal Physiology and Overall Development Strategy.

The gastrointestinal (GI) tract is one of the most popular and used routes of drug product administration due to the convenience for better patient compliance and reduced costs to the patient compared to other routes. However, its complex nature poses a great challenge for formulation scientists when developing more complex dosage forms such as those combining two or more drugs. Fixed dose combination (FDC) products are two or more single active ingredients combined in a single dosage form. This formulation strategy represents a novel formulation which is as safe and effective compared to every mono-product separately. A complex drug product, to be dosed through a complex route, requires judicious considerations for formulation development. Additionally, it represents a challenge from a regulatory perspective at the time of demonstrating bioequivalence (BE) for generic versions of such drug products. This report gives the reader a summary of a 2-day short course that took place on the third and fourth of November at the Annual Association of Pharmaceutical Scientists (AAPS) meeting in 2018 at Washington, D.C. This manuscript will offer a comprehensive view of the most influential aspects of the GI physiology on the absorption of drugs and current techniques to help understand the fate of orally ingested drug products in the complex environment represented by the GI tract. Through case studies on FDC product development and regulatory issues, this manuscript will provide a great opportunity for readers to explore avenues for successfully developing FDC products and their generic versions.

Development and Optimization of a Wet Granulation Process at Elevated Temperature for a Poorly Compactible Drug Using Twin Screw Extruder for Continuous Manufacturing.

The objective of this study was to enhance tabletability of a poorly compactible drug, acetaminophen, by wet granulation using twin screw extruder at high temperature. It was desired that there would be minimum amounts of excipients used and the granules obtained after extrusion would be dry and fall within a size range suitable for tableting without any further processing. Mixtures of acetaminophen (95%) with binders (5% povidone or partially pregelatinized starch) were wet granulated through twin screw extruder at 70°C by adding 7% w/w water. The process had a short granulation time (<1 min), and, on account of the elevated processing temperature used, no drying after extrusion was needed. By optimizing formulation and processing parameters, >90% granules in the size range of 125 to 1000 µm (<3% above 1000 µm and <7% below 125 µm) were obtained without any milling. When the granules were compressed by adding 1% disintegrant and 0.5% lubricant extragranularly, tablets produced (93.6% drug load) had good mechanical strength having hardness >1.7 MPa, which was superior to that of tablets prepared by conventional high shear wet granulation. As the granules could be extruded continuously and did not require drying and milling, the method was amenable to continuous processing.

Assessment of Tablet Surface Hardness by Laser Ablation and Its Correlation With the Erosion Tendency of Core Tablets.

Surface erosion of uncoated tablets results in processing problems such as dusting and defects during coating and is governed by the strength of particle bonding on tablet surface. In this study, the correlation between dusting tendency of tablets in a coating pan with friability and laser ablation surface hardness was assessed using tablets containing different concentrations of magnesium stearate and tartaric acid. Surface erosion propensity of different batches was evaluated by assessing their dusting tendency in the coating pan. In addition, all tablets were analyzed for crushing strength, friability, modified friability test using baffles in the friability apparatus, and weight loss after laser ablation. Tablets with similar crushing strength showed differences in their surface erosion and dusting tendency when rotated in a coating pan. These differences did not correlate well with tablet crushing strength or friability but did show reasonably good correlation with mass loss after laser ablation. These results suggest that tablet surface mass loss by laser ablation can be used as a minipiloting (small-scale) tool to assess tablet surface properties during early stages of drug product development to assess the risk of potential large-scale manufacturing issues.

Impact of moisture and magnesium stearate functionality on manufacturability of wet granulated metformin tablets.

During the development of a wet granulated 850 mg metformin hydrochloride tablet formulation, the tablets exhibited high friability (>3% w/w) irrespective of the source of extra-granular magnesium stearate (MgSt). High friability values indicated that an anti-bonding effect of MgSt was too high to be overcome by 3.3% w/w povidone as a binder in the formulation with 1.5% w/w residual granule moisture. Increasing the povidone concentration up to 7% w/w showed limited improvement in friability, with tablets showing variable friability depending on MgSt source. Characterization of MgSt indicated differences in crystallinity, surface area and particle morphology between different vendors. In addition, a new bulk yield strength test, which determines the MgSt fragmentation tendency, was found to be indicative of the MgSt performance in the tablet formulation. To improve bonding properties of granules, residual granule moisture was increased to 2% w/w at different povidone concentrations. At 2% w/w residual granule moisture content, regardless of MgSt source, the tablets showed significant improvement in friability (∼0.6% w/w) even at the lowest povidone concentration (3.3% w/w). The bonding power of higher residual granule moisture had a greater impact than higher povidone concentration in overcoming the anti-bonding effects of magnesium stearate.

Advances in mechanistic understanding of release rate control mechanisms of extended-release hydrophilic matrix tablets.

Approaches to characterizing and developing understanding around the mechanisms that control the release of drugs from hydrophilic matrix tablets are reviewed. While historical context is provided and direct physical characterization methods are described, recent advances including the role of percolation thresholds, the application on magnetic resonance and other spectroscopic imaging techniques are considered. The influence of polymer and dosage form characteristics are reviewed. The utility of mathematical modeling is described. Finally, how all the information derived from applying the developed mechanistic understanding from all of these tools can be brought together to develop a robust and reliable hydrophilic matrix extended-release tablet formulation is proposed.

Food Effect in Humans: Predicting the Risk Through In Vitro Dissolution and In Vivo Pharmacokinetic Models.

In vitro and in vivo experimental models are frequently used to assess a new chemical entity's (NCE) biopharmaceutical performance risk for food effect (FE) in humans. Their ability to predict human FE hinges on replicating key features of clinical FE studies and building an in vitro-in vivo relationship (IVIVR). In this study, 22 compounds that span a wide range of physicochemical properties, Biopharmaceutics Classification System (BCS) classes, and food sensitivity were evaluated for biorelevant dissolution in fasted- and fed-state intestinal media and the dog fed/fasted-state pharmacokinetic model. Using the area under the curve (AUC) as a performance measure, the ratio of the fed-to-fasted AUC (FE ratio) was used to correlate each experimental model to FE ratio in humans. A linear correlation was observed for the in vitro dissolution-human IVIVR (R (2) = 0.66, % mean square error 20.7%). Similarly, the dog FE ratio correlated linearly with the FE ratio in humans (R (2) = 0.74, % mean square error 16.25%) for 15 compounds. Data points near the correlation line indicate dissolution-driven mechanism for food effect, while deviations from the correlation line shed light on unique mechanisms that can come into play such as GI physiology or unusual physicochemical properties. In summary, fed/fasted dissolution studies and dog PK studies show a reasonable correlation to human FE, hence are useful tools to flag high-risk NCEs entering clinical development. Combining kinetic dissolution, dog FE model and in silico modeling one can study FE mechanism and formulation strategies to mitigate the FE risk.

Wetting effects versus ion pairs diffusivity: interactions of anionic surfactants with highly soluble cationic drugs and its impact on tablet dissolution.

A study was conducted to develop a mechanistic understanding of dissolution of a highly soluble cationic drug, metformin hydrochloride, under the influence of anionic surfactants, sodium alkyl sulfates. The surfactants did not influence the saturated solubility of the drug, but reduced the surface tension of the dissolution media as the alkyl chain length increased. Their influence on tablet wetting based on the contact angles did not show any trend. The dissolution of 850 mg metformin hydrochloride tablets in 0.1 N HCl and pH 4.5 acetate buffer with 0.01% (w/v) sodium n-octyl sulfate (C8), sodium n-decyl sulfate (C10), or sodium n-tetradecyl sulfate (C14) was similar to the control, but was enhanced by sodium lauryl sulfate (C12). At 0.1% (w/v) concentration, the dissolution was not enhanced by C12 because the reduction in surface tension was counterbalanced by an increase in hydrophobic ion pairs that showed slower diffusivity by nuclear magnetic resonance. At 0.1% (w/v), metformin also formed an insoluble salt (1:2 molar ratios) with C10 (pH 1.2), C12, and C14 (pH 1.2 and 4.5) but not with C8. Three competing factors influenced the drug dissolution by surfactants: reduction in surface tension of the dissolution media, ion pairs with low diffusivity, and formation of an insoluble salt.

Influence of dissolution media pH and USP1 basket speed on erosion and disintegration characteristics of immediate release metformin hydrochloride tablets.

PURPOSE: To investigate the influence of the pH of the dissolution medium on immediate release 850 mg metformin hydrochloride tablets. METHODS: A traditional wet granulation method was used to manufacture metformin hydrochloride tablets with or without a disintegrant. Tablet dissolution was conducted using the USP apparatus I at 100 rpm. RESULTS: In spite of its pH-independent high solubility, metformin hydrochloride tablets dissolved significantly slower in 0.1 N HCl (pH 1.2) and 50 mM pH 4.5 acetate buffer compared with 50 mM pH 6.8 phosphate buffer, the dissolution medium in the USP. Metformin hydrochloride API compressed into a round 1200 mg disk showed a similar trend. When basket rotation speed was increased from 100 to 250 rpm, the dissolution of metformin hydrochloride tablets was similar in all three media. Incorporation of 2% w/w crospovidone in the tablet formulation improved the dissolution although the pH-dependent trend was still evident, but incorporation of 2% w/w croscarmellose sodium resulted in rapid pH-independent tablet dissolution. CONCLUSION: In absence of a disintegrant in the tablet formulation, the dissolution was governed by the erosion-diffusion process. Even for a highly soluble drug, a super-disintegrant was needed in the formulation to overcome the diffusion layer limitation and change the dissolution mechanism from erosion-diffusion to disintegration.

Controlling the chemical stability of a moisture-sensitive drug product through monitoring and identification of coating process microenvironment.

The objective of this work was to monitor and identify the impact of coating microenvironment, as measured by PyroButtons(®) data loggers, on the chemical stability of a moisture-sensitive drug molecule brivanib alaninate (BA). BA tablets were coated at two different scales (15 and 24 in pan). PyroButtons(®) data loggers were allowed to move freely within the tablet bed to record the temperature and relative humidity conditions of the tablet bed. The tablet moisture content at the end of the coating runs, and the rate of hydrolysis of the BA tablets based on HPLC analysis was found to be a function of the coating thermodynamic microenvironment. Wetter coating conditions resulted in tablets with higher water content and showed greater degradation upon storage. The coating process which yielded acceptable stability in a 15 in coater was transferred to a 24 in coater by maintaining similar tablet-bed relative humidity and temperature conditions. This was compared to a traditional scale-up approach where the environmental equivalency factor (EEF) was matched between scales during coating. The moisture content observed across the two scales indicated that maintaining a similar tablet-bed microenvironment ensured consistent results between scales.

Surfactant-mediated dissolution of metformin hydrochloride tablets: wetting effects versus ion pairs diffusivity.

The aqueous solubility of metformin (pKa: 2.8 and 11.5) in the pH range of 1.2-6.8 is 300 mg/mL. Thus, the dissolution of metformin hydrochloride tablets should be pH independent. However, 850 mg metformin hydrochloride tablets dissolved more slowly in pH 1.2 and 4.5 dissolution media than in pH 6.8 medium. It is hypothesized that the additional protonation of metformin at the acidic pH results in higher solvation and a larger hydrodynamic radius, leading to slower diffusion and dissolution. This hypothesis was supported by the observation that cationic metformin and anionic sodium lauryl sulfate (SLS), 0.1% (w/v), formed an insoluble salt (1:2 molar ratio) at pH 1.2 and 4.5, but not at pH 6.8. SLS at 0.01% (w/v) in all three media enhanced metformin dissolution. The slower metformin dissolution at pH 1.2 and 4.5 media with SLS can be attributed to the formation of metformin-lauryl sulfate (Met-LS) (1:2 and 1:1) ion pairs, which are more hydrophobic than Met-LS (1:1) ion pairs at pH 6.8. Slower metformin diffusivity in pH 4.5 with 0.05% (w/v) SLS was observed by diffusion-ordered spectroscopy nuclear magnetic resonance. Improved metformin wetting by SLS outweighed the lower diffusivity of metformin-LS ion pairs because similar enhancement in dissolution was noted with 0.5% (w/v) nonionic polysorbate 80.

Solubilization of entecavir by povidone to overcome content uniformity challenges for low-dose tablet formulations.

Development of 0.1, 0.5, and 1.0 mg entecavir tablet formulations for the treatment of hepatitis B virus was challenging for content uniformity. Entecavir with pKa of 2.8 and 9.8 does not have sufficient solubility in acidic or alkaline medium or in common pharmaceutical solvents such as ethanol to dissolve the drug in granulating fluid to prepare the homogeneous granulation. Povidone (PVP), a commonly used binder, was found to increase entecavir solubility depending on the PVP concentration and temperature of the solution. At 15% w/w PVP concentration, entecavir solubility increased from 2 mg/mL to about 8 mg/mL at room temperature. When the PVP solution was heated to 50°C or 70°C, the solubility was increased to about 23 or 33 mg/mL, respectively. Based on Raman spectra of entecavir in PVP solution, the increase in entecavir solubility in the presence of PVP may not be due to any molecular interactions between them. Solubilization of entecavir in PVP and eventual granulation did not change the polymorphic form of the drug based on the powder X-ray and differential scanning calorimetric (DSC), and thermo-gravimetric analysis (TGA) of neat entecavir re-crystallized from the PVP solution. The enhancement in the solubility of entecavir by PVP was sufficient to keep the amount of solution, which was used for granulation, to be about 20% w/w of the batch size like the traditional aqueous granulation. The granulation manufactured using this approach provided better tablet content uniformity than one using micronized entecavir.

Formulation design, challenges, and development considerations for fixed dose combination (FDC) of oral solid dosage forms.

Fixed dose combination (FDC) products are common in the treatment of hypertension, diabetes, human immunodeficiency virus, and tuberculosis. They make it possible to combine two or more drug molecules with different modes of pharmacological actions in a single dosing unit and optimize the treatment. From a patient perspective, they offer convenience, reduced dosing unit burden, and cost savings. From a clinical perspective, aging population in developed countries will need multiple medications to treat age related diseases and co-morbidities. FDC products simplify dosing regimen and enhance patient compliance. As outlined in the article, the number of FDC products has grown over the years and the trend is likely to continue. This review article gives an overview to pharmaceutical scientists about recent trends in the formulation development of the FDC products and provides decision trees to select most optimum formulation development strategy. While some formulation technologies such as multi-layer tablets, multiparticulate systems, active film coating, and hot-melt granulation are discussed in more detail, a few specialized technologies are also introduced briefly to the readers.

Physicochemical interactions in solid dosage forms.

Complete characterization and mechanistic understanding of physicochemical interactions in solid dosage forms are not only important for consistent manufacturability, stability, and bioavailability of the drug product, but are also expected under the quality-by-design paradigm of drug development. Lack of this understanding can impact successful and timely development, scale-up, and commercial manufacture of dosage forms. This article highlights the stability and bioavailability implications of physicochemical interactions in dosage forms citing a couple of examples where such interactions necessitated the recall of commercial drug products.

Impact of excipient interactions on solid dosage form stability.

Drug-excipient interactions in solid dosage forms can affect drug product stability in physical aspects such as organoleptic changes and dissolution slowdown, or chemically by causing drug degradation. Recent research has allowed the distinction in chemical instability resulting from direct drug-excipient interactions and from drug interactions with excipient impurities. A review of chemical instability in solid dosage forms highlights common mechanistic themes applicable to multiple degradation pathways. These common themes include the role of water and microenvironmental pH. In addition, special aspects of solid-state reactions with excipients and/or excipient impurities add to the complexity in understanding and modeling reaction pathways. This paper discusses mechanistic basis of known drug-excipient interactions with case studies and provides an overview of common underlying themes. Recent developments in the understanding of degradation pathways further impact methodologies used in the pharmaceutical industry for prospective stability assessment. This paper discusses these emerging aspects in terms of limitations of drug-excipient compatibility studies, emerging paradigms in accelerated stability testing, and application of mathematical modeling for prediction of drug product stability.

An evaluation of process parameters to improve coating efficiency of an active tablet film-coating process.

Effects of material and manufacturing process parameters on the efficiency of an aqueous active tablet film-coating process in a perforated pan coater were evaluated. Twenty-four batches representing various core tablet weights, sizes, and shapes were coated at the 350-500 kg scale. The coating process efficiency, defined as the ratio of the amount of active deposited on tablet cores to the amount of active sprayed, ranged from 86 to 99%. Droplet size and velocity of the coating spray were important for an efficient coating process. Factors governing them such as high ratios of the suspension spray rate to atomization air flow rate, suspension spray rate to pattern air flow rate, or atomization air flow rate to pattern air flow rate improved the coating efficiency. Computational fluid dynamics modeling of the droplets showed that reducing the fraction of the smaller droplets, especially those smaller than 10 µm, resulted in a marked improvement in the coating efficiency. Other material and process variables such as coating suspension solids concentration, pan speed, tablet velocity, exhaust air temperature, and the length of coating time did not affect the coating efficiency profoundly over the ranges examined here.

An active film-coating approach to enhance chemical stability of a potent drug molecule.

Peliglitazar, a PPAR α/γ agonist, was found to undergo acid as well as base catalyzed degradation. The acid catalyzed degradation led to the formation of benzylic alcohol and glycine carbamate and the base catalyzed degradation led to formation of p-hydroxyanisole and an amine degradant. In capsule formulations, the capsules with the lowest drug-loading exhibited maximum instability even at 25 °C/60% RH storage condition. Incorporation of pH-modifiers to maintain 'micro-environmental pH' acidic did not prevent the formation of the base-catalyzed degradants. Traditional dry granulated tablet formulation which is qualitatively similar to the capsule formulations showed the presence of acid-catalyzed degradants even without the presence of an acidifying agent. On the other hand, traditional wet granulated tablet formulation showed mainly base-catalyzed degradants. Stability problems of the tablet formulation were aggravated because the potent molecule required low tablet strengths which resulted in low drug to excipient ratio. To stabilize the molecule, an active film-coating approach was explored. In this approach, the drug was sprayed with the coating material onto non-active containing tablet cores. This approach of trapping the drug particles into the coating material provided tablets with satisfactory chemical stability. The stability enhancement observed in the active coating approach is attributed to the higher drug to excipient ratio in the film coat of non-reactive coating material compared to that in the traditional dry or wet granulated formulations.