Developing an injectable formula containing an oxygen-sensitive drug: a case study of danofloxacin injectable

The purpose of this study was to assess the impact of impurities in formulation components, antioxidants, formulation pH, and processing/packaging on the extent of color change associated with oxidation of danofloxacin injectable. The methods used in this study include reversed-phase HPLC, UV-VIS spectrophotometry, atomic absorption spectroscopy, visual observation, and iodimetric titration for quantification of the antioxidant. The results from this study revealed that trace impurities from two different excipients significantly contributed to color change associated with oxidation. Polyvinyl pyrrolidone (PVP) introduced trace levels of peroxides into the solution. A second excipient also had a significant impact on stability because it introduced trace metal impurities into the product. The minimization of oxygen levels alone in the solution and headspace was not sufficient to completely eliminate the product instability. The addition of an antioxidant, monothioglycerol (MTG), resulted in a formulation less sensitive to processing variables. The impact of pH on the performance of MTG was also studied. At pH 7.5, MTG resulted in significant improvement in stability; however, at pH 6.0 it was not effective as an antioxidant. Process modifications alone may not be sufficient to prevent oxidation. Chemical approaches, such as pH control, addition of an antioxidant, and control of components should be considered first as means of enhancing stability of oxygen-sensitive solutions.     

Formulation development and manufacturing of a gastrin/CCK-2 receptor targeting peptide as an intermediate drug product for a clinical imaging study.

A DOTA-gastrin analogue (APH070) which, when labelled with (111)In, has high affinity for the gastrin/CCK-2 receptor (3nM) and low tumour to kidney ratio in animal models, has been formulated and manufactured for a clinical study. Oxidation of the peptide methionine residue greatly reduces receptor affinity, therefore development work focused on producing a stable intermediate drug product (iDP) whilst ensuring that the formulation, container, closure and manufacturing process did not inhibit the extremely sensitive radiolabelling reaction (itself a source of oxidation). Stress testing revealed that APH070 was stable at 2-8 degrees C at pH 6-9. Addition of an antioxidant (monothioglycerol) to the peptide formulation reduced stability when compared to buffer alone. Use of FluroTec (4023/50) stoppers (rather than FluroTec Plus (4110/40)) increased both the stability and radiolabelling efficiency of APH070. Long term stability (6 months) of the final formulation (1mg/ml APH070 in 0.01 M pH 7.2 phosphate buffer) stored at 5 degrees C in type I glass vials with FluroTec (4023/50) stoppers was 98.6+/-0.2% and 98.4+/-0.1% for upright and inverted samples, respectively. Clinical scale radiolabelling of the final formulation routinely achieves the specification of >85% (111)In-APH070 (unoxidised) stable for up to 2h after dilution with 0.9% w/v saline solution. Specific uptake of the radiopharmaceutical in CCK-2R-expressing AR42J tumours in nude mice has been demonstrated.     

The Degradation Chemistry of GSK2879552: Salt Selection and Microenvironmental pH Modulation to Stabilize a Cyclopropyl Amine

The cyclopropyl amine moiety in GSK2879552 (1) degrades hydrolytically in high pH conditions. This degradation pathway was observed during long-term stability studies and impacted the shelf life of the drug product. This article describes the work to identify the degradation impurities, elucidate the degradation mechanism, and design a stable drug product. It was found that salt selection and control of the microenvironmental pH of the drug product formulation blend significantly improved the chemical stability of the molecule in the solid state.     

Residue-Specific Impact of EDTA and Methionine on Protein Oxidation in Biotherapeutics Formulations Using an Integrated Biotherapeutics Drug Product Development Workflow

The rational design and selection of formulation composition to meet molecule-specific and product-specific needs are critical for biotherapeutics development to ensure physical and chemical stability. This work, based on three antibody-based (mAb) proteins (mAbA, mAbB, and mAbC), evaluates residue-specific impact of EDTA and methionine on protein oxidation, using an integrated biotherapeutics drug product development workflow. This workflow includes statistical experimental design, high-throughput experimental automation and execution, structure-based in silico modeling, inferential statistical analysis, and enhanced interactive data visualization of large datasets. This oxidation study evaluates the impact of formulation parameters including pH, protein concentration, and the presence of polysorbate 80 on the oxidation of specific conserved and variable residues of mAbs A, B, and C in the presence of stressors (iron, peroxide) and/or protectants (EDTA, L-methionine). Residue-specific analysis by automated high-throughput peptide mapping demonstrates differential residue-specific effects of EDTA and methionine in protecting against oxidation, highlighting the need for molecule-specific and product-specific selection of these excipients during formulation development. Computational modeling based on a homology model and the two-shell water coordination method (WCN) was employed to gain mechanistic understanding of residue-specific oxidation susceptibility of methionine residues. The computational determinants of local solvent exposure of methionine residues showed good correlation of WCN with experimentally determined oxidation for corresponding residues. The rapid generation of high-resolution data, statistical data analysis and interactive visualization of the high-throughput residue-level data containing ～200 unique formulations facilitate residue-specific, molecule-specific and product-specific oxidation (global and local) assessment for oxidation protectants during early development for mAbs and related mAb-based modalities.     

Impurities in a lyophilized formulation of BMS-204352: identification and role of sanitizing agents

The purpose of this study was to identify two impurities in the parenteral lyophilized formulation of BMS-204352, investigate the role of sanitizing agents as their potential source, evaluate their effect on drug product stability, and develop a strategy to prevent their contamination of the drug product. The two impurities were identified as o-phenylphenol and 4-t-amylphenol based on liquid chromatography/mass spectroscopy (LC/MS) and chromatographic comparison to authentic samples. The LC/MS spectra of commercially available o-phenylphenol and 4-t-amylphenol showed identical patterns of fragmentation and the same retention times as the impurities identified in the BMS-204352 lyophilized product. Levels of these impurities were low and ranged between 0.2-0.3 microg/vial as determined by HPLC and using an authentic external reference standard. To confirm the hypothesis that the commercial sanitizing agents used in the sterile area were the source of these phenolic impurities, several product samples were spiked with the sanitizing agents. Both o-phenylphenol and 4-t-amylphenol were detected in the spiked samples. Further investigation revealed that o-phenylphenol and 4-t-amylphenol are active ingredients of these commercial sanitizing agents. Drug product samples containing the phenolic impurities showed no potency loss following storage at 30, 50, and 70 degrees C indicating these impurities had no adverse effect on product stability. These studies suggest that sanitizing agents used in the sterile area, although may be present at trace levels below typical cleaning procedure detection methods, need to be properly controlled and closely monitored during the manufacturing of injectable products, particularly highly potent drugs. Sanitizing agents, even though not used on product contact surfaces, may potentially contaminate a product through vapor transfer in an open environment.     

Impurities in a Lyophilized Formulation of BMS-204352: Identification and Role of Sanitizing Agents

The purpose of this study was to identify two impurities in the parenteral lyophilized formulation of BMS-204352, investigate the role of sanitizing agents as their potential source, evaluate their effect on drug product stability, and develop a strategy to prevent their contamination of the drug product. The two impurities were identified as o-phenylphenol and 4-t-amylphenol based on liquid chromatography/mass spectroscopy (LC/MS) and chromatographic comparison to authentic samples. The LC/MS spectra of commercially available o-phenylphenol and 4-t-amylphenol showed identical patterns of fragmentation and the same retention times as the impurities identified in the BMS-204352 lyophilized product. Levels of these impurities were low and ranged between 0.2–0.3 μg/vial as determined by HPLC and using an authentic external reference standard. To confirm the hypothesis that the commercial sanitizing agents used in the sterile area were the source of these phenolic impurities, several product samples were spiked with the sanitizing agents. Both o-phenylphenol and 4-t-amylphenol were detected in the spiked samples. Further investigation revealed that o-phenylphenol and 4-t-amylphenol are active ingredients of these commercial sanitizing agents. Drug product samples containing the phenolic impurities showed no potency loss following storage at 30, 50, and 70°C indicating these impurities had no adverse effect on product stability. These studies suggest that sanitizing agents used in the sterile area, although may be present at trace levels below typical cleaning procedure detection methods, need to be properly controlled and closely monitored during the manufacturing of injectable products, particularly highly potent drugs. Sanitizing agents, even though not used on product contact surfaces, may potentially contaminate a product through vapor transfer in an open environment.     

Effect of irradiation on parathyroid hormone PTH(1–34) coated on a novel transdermal microprojection delivery system to produce a sterile product—adhesive compatibility

Terminal sterilization via γ‐irradiation or e‐beam and aseptic processing were evaluated as a means to manufacture the sterile product of parathyroid hormone 1–34 coated on a novel transdermal microprojection delivery system. The main difference of the two methods is the inclusion and exclusion of the coated formulation for irradiation during terminal sterilization and aseptic processing, respectively. Both γ‐irradiation and e‐beam of the final product resulted in increased PTH(1–34) oxidation, which could be reduced by lowering the irradiation dose or the irradiation temperature. Minimizing moisture and oxygen levels inside the primary packaging could effectively limit PTH oxidation to <2% initially, but the stability continued deteriorating to fall below the purity specification over 3‐month storage. Aseptic processing has its own challenge as one of the device components, acrylic‐based adhesive, was found to be incompatible with the peptide due to volatile compound(s) released from the irradiated adhesive. Although the nature of the volatile compounds was not fully understood, we developed a screening method capable of rapidly and effectively identifying an alternate adhesive. This study proved that aseptic processing is the choice of the sterile manufacturing approach and wouldn't compromise the target of achieving ≥2‐year, ambient‐temperature storage stability. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2123–2134, 2010     

Stability of aqueous solutions of mibolerone.

The kinetics and mechanism of degradation of mibolerone were studied in aqueous buffered solutions in the pH range of 1-8 at 67.5 degrees. Mibolerone showed maximum stability between pH 5.5 and 6.4. At pH 1-2, the major degradative pathway was dehydration followed by migration of the 18-methyl group to form 7alpha,17,17-trimethylgona-4,13-dien-3-one. While there was only one degradation product at pH 1-2, the degradation at pH 7-8 was complex. As many as 12 degradation products were detected by GLC. Mass spectral data indicated that the majority of these products were either oxidation products or isomers. At pH 7.6, the apparent first-order rate constants exhibited marked dependency on buffer concentration. Incorporation of a sequestering agent into the solutions eliminated this dependency, suggesting that trace metal impurities from the buffer reagents were catalyzing the degradation. This was confirmed by degradation studies of solutions in water for injection containing 5 ppm of trace metal ions. Sn+2, Cu"2, and Fe+2 accelerated the degradation, with Fe+2 having the most catalytic effect. The temperature dependence of the rate of degradation was studied in 0.05 M phosphate buffer at pH 6.4. The activation energy was 19.6 +/- 1.63 kcal/mole.     

High speed development work by preparation of an "in-hand" library of NMR-quantified degradation products

Standard materials of impurities are needed in pharmaceutical development such as for validating impurity analytical methods. Most often the impurities possess structures, which are difficult and very time consuming to synthesize. In the present work, we demonstrate that a library of degradation products of ragaglitazar--a novel tricyclic-gamma-alkyloxyphenylpropionic acid with hypolipidemic and antidiabetic activity--observed in stability indicating samples of a solid dosage formulation by LC-MS can be produced in a one pot oxidation reaction. The library entities were isolated in small quantities (microg-mg) by preparative HPLC and structurally characterized by NMR spectroscopy and mass spectrometry. The concentrations of the library entities were determined in solution by NMR using an internal standard method. The library was successfully used in the validation work of a newly developed purity method for the drug product providing useful response factors and relative retention times (RRTs) of the degradation products.     

复方苯酚溶液中抗氧剂的筛选

目的:筛选复方苯酚溶液的抗氧剂,以提高其稳定性。方法:采用经典恒温法和留样观察法对7份含有不同抗氧剂(0、0.1%、0.15%、0.2%浓度的硫代硫酸钠和亚硫酸钠)的复方苯酚溶液中苯酚含量、溶液pH值及外观颜色进行考察,并预测溶液的有效期,优选出有效期最长的处方;采用稀释法测定优选处方及未加抗氧剂的对照处方的最低杀菌浓度(MBC),考察抗氧剂的加入对杀菌作用的影响。结果:以0.1%硫代硫酸钠为抗氧剂的处方中苯酚含量、pH值及外观颜色的变化均较其它6份处方小,有效期为8.5个月,MBC值与对照处方相同。结论:复方苯酚溶液中加入0.1%硫代硫酸钠作为抗氧剂可提高溶液稳定性且不影响杀菌效果。     

硫酸庆大霉素注射液处方和工艺研究

目的 研究硫酸庆大霉素注射液的处方和工艺,提高其Ph稳定性.方法 考察了配制浓料的注射用水温度、抗氧剂用量及其加入顺序对Ph稳定性的影响,按照最终确定的处方和工艺配制3批样品进行加速试验及长期稳定性试验.结果 在硫酸庆大霉素注射液生产中,配制浓料的注射用水温度和抗氧剂的加入顺序对Ph稳定性有影响,抗氧剂用量对Ph稳定性几乎无影响.结论 最终确定的处方和工艺比较合理,适用于大规模生产.     

Formulation of a stable parenteral product; Clonidine Hydrochloride Injection

Clonidine Hydrochloride Injection (Duraclon) is a clear, colorless, preservative-free, pyrogen free, aqueous solution of clonidine hydrochloride. The indication for this product is for use as an adjunct in pain management, administered epidurally, when opiates are insufficient. The drug formulation was evaluated under both normal and stress conditions in the preformulation/formulation studies. The list of studies conducted includes a light sensitivity study, an oxygen sensitivity study, a pH/stability study, a stopper compatibility evaluation, a freeze-thaw study, and a stability study. Samples from the light, oxygen, pH/stability, and stability studies were evaluated for color, visual clarity, pH, potency, and chromatographic purity. Samples from the freeze-thaw study were evaluated for all of the above except chromatographic purity. The results for these studies demonstrate the stability of the product as formulated. The pH of this unbuffered product was consistently within the acceptance criteria. The product remained clear and colorless for the duration of each study. The values obtained for the potency and chromatographic purity assays showed no evidence of degradation. The reasons for the lack of degradation can be found in the molecular structure of the drug substance and the formulation of the drug product. Since the molecular structure is that of a Schiff base, it is theoretically possible, although difficult, to cleave the molecule. A catalyst would be required, and none of the possible catalysts are present in the formulation. The molecule could also be cleaved upon exposure to light, and the evidence indicates that the molecule does interact with light. This interaction is not to the degree, however, that product stability is affected. The formulation contains only the active drug substance and sodium chloride in water for injection with a pH of approximately 6. Although the product is unbuffered, the influence of the stoppers and glass vials upon the formulation pH was minimal. In addition, the stopper compatibility of the product is enhanced by the absence of chelating agents, preservatives, acids, and bases. Since the dilute concentrations of both the active and excipient are well below their solubility limits, no solubility related issues would be expected upon freezing and subsequent thawing. Clonidine Hydrochloride Injection, as formulated, does not require protection from light, oxygen, or freezing. The product shows acceptable stability within the pH range, and the rubber closure is compatible with the product. Real time stability data combined with statistical projections support a 36-month expiration date.     

注射用泮托拉唑钠的稳定性考察

目的:考察注射用泮托拉唑钠在4种输液中的稳定性。方法:采用高效液相色谱法测定注射用泮托拉唑钠与4种输液配伍 后在4h内的含量变化,并观察溶液外观;同时考察钾、镁、钙离子及pH值变化对注射用泮托拉唑钠稳定性的影响。结果:注射用泮 托拉唑钠在4种常用输液以及钾、镁、钙离子水溶液中于4h内其含量、外观、pH值、最大紫外吸收波长均无明显改变。溶液pH值 低于7．0时泮托拉唑钠极不稳定;pH值为7．0时,颜色可出现微黄变化,但含量降低不明显;溶液pH值在8．0以上时泮托拉唑钠 在4h内稳定。结论:注射用泮托拉唑钠在4种常用输液以及钾、镁、钙离子水溶液中于4h内可保持稳定,pH值对泮托拉唑钠溶液 的稳定性影响较大。     

The Effects of Formulation Additives on the Degradation of Freeze-Dried Ribonuclease A

The stability of a freeze-dried model protein, ribonuclease A (RNase), was investigated under accelerated storage conditions at 45°C for time periods up to 60 days. Because RNase is a fairly stable molecule around pH 7, lyophilization was performed in phosphate buffers at pH 4.0 or 10.0 to accelerate degradation kinetics. Degradation was studied by measuring enzymatic activity, the concentrations of soluble monomeric RNase, soluble aggregated (polymerized) RNase, and insoluble aggregated RNase following reconstitution of the lyophilized material at different times. The presence of air in the vial headspace accelerated degradation in the solid state in all cases. When argon or nitrogen was employed in the headspace, degradation kinetics were reduced, implying that molecular oxygen was involved in the degradation process. This interpretation was supported by the observation that 0.05% (w/v) EDTA in the formulation prior to freeze-drying retarded RNase degradation dramatically. EDTA was believed to chelate cations which may have been introduced with the buffer salts in trace quantities sufficient to catalyze autoxidation reactions. Incorporation of antioxidants ascorbic acid (at pH 4.0) and POBN (a spin trap which could have functioned as an antioxidant at pH 10.0) accelerated the degradation of RNase and appeared, in both cases, to be involved in interactions with the protein molecules. Additionally, in the presence of the antioxidants RNase degradation appeared to be accelerated by light. Although there is strong support for the oxidative hypothesis, the possibility of other competing reactions cannot be discounted. These investigations demonstrate the importance of challenging the extrapolation of some of our well-established ideas concerning small molecule solution kinetics to macromolecules in the solid state.     

The safety,stability, and compatibility of fragrances in skin and hair products†

Abstract

The efforts of the formulating chemist, perfumer, and toxicologist represent the creative forces that ultimately merge to accomplish a finished formulation. Because the ingredients in a compounded fragrance are proprietary to the company that produces them, the formulating chemist must add a mixture of unknown substances to his basic formulation with the hope that they will be compatible in functionality, stability, and safety. A well-controlled stability and safety testing program is needed to assure complete compatibility between the base formulation and the fragrance.

Potential stability problems include changes in viscosity, color, odor, clarity of transparent systems, and emulsion stability. These changes may be caused by hydrolysis, oxidation, reaction to light, reaction to metals, insolubilities, reaction to processing conditions, and packaging materials. The interactions which occur during these changes can cause the formation of new materials that may have irritation or sensitization potential. We recommend that samples of product that have successfully passed shelf-life testing be furnished to the toxicologist for a complete battery of safety tests, including controlled use testing. This procedure should help to assure that untoward reactions do not occur during consumer use.     

On Developing a Process for Conducting Extractable–Leachable Assessment of Components Used for Storage of Biopharmaceuticals

Extractables and leachables are product‐related impurities that result from product contact with components such as gaskets, stoppers, storage bags, cartridges, and prefilled syringes that are used for processing, storage, and/or delivery of biopharmaceuticals. These impurities are a concern for patients due to potential effects on product quality and safety. It is possible that such an impurity could directly impact the patient or indirectly impact the patient by interacting with the protein therapeutics and forming protein adducts. Adducts and leachables may or may not be detected as product‐related impurities in routine stability indicating assays depending on the rigor of the analytical program. The need for the development of a thorough and holistic extractable and leachable program based on risk assessment, review of existing literature, and consolidation of industry best practices is discussed. Standardizing component use within an organization enables streamlining of the extractable–leachable program. Our strategy for an extractable–leachable program is divided into different stages, each stage detailing the activities and the department within the organization that is responsible for execution of these activities. The roles and responsibilities of the key stakeholders are identified. The integration of analytical activities with health‐based risk‐assessment information into the design of an extractable–leachable program is highlighted. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2209–2218, 2010     

清炒法炮制粉葛过程中主要化学成分与工艺、物性及颜色变化的相关性分析

目的：研究清炒法炮制过程中粉葛主要化学成分与工艺、物性及颜色的动态变化,以及其相关性。方法：测定不同炮制阶段粉葛样品的物性参数（氧化值、膨胀度、堆密度、pH值）,利用影像设备、Photoshop软件等获取炮制品图片的颜色变化值,采用紫外分光光度苯酚-硫酸显色法测定粉葛中可溶性多糖的含量,运用双波长法测定粉葛中总淀粉含量,最后对参数进行配对样本t检查、方差分析及线性回归分析。结果：随着炮制程度的加强,粉葛中总淀粉含量降低,水溶性多糖的含量先增高再降低,两者呈负相关。粉葛中可溶性多糖的含量与氧化性、红-绿色轴值呈明显正相关性,与膨胀度成明显负相关,淀粉含量与堆密度呈明显负相关。主要化学成分与部分物性参数及色度值线性回归显著。结论：粉葛在清炒法炮制过程中,参数间可能存在转化。部分颜色变化和物性参数数据可以作为评价炮制程度及合格与否的标准,弥补传统人为判断造成炮制品质量无法统一的不足,从而规范生产工艺。     

Succinate Buffer in Biologics Products: Real-world Formulation Considerations,Processing Risks and Mitigation Strategies

The succinic acid/succinate system has an excellent buffering capacity at acidic pH values (4.5-6.0), promising to be a buffer of choice for biologics having slightly acidic to basic isoelectric points (pI 6 – 9). However, its prevalence in drug products is limited due to the propensity (risk) of its components to crystallize during freezing and the consequent shift in the pH which might affect the product stability. Most of these previous assessments have been performed under operational conditions that do not simulate typical drug product processing conditions. In this work, we have characterized the physicochemical behavior of succinate formulations under representative pharmaceutical conditions. Our results indicate that the pH increases by ～ 1.2 units in 25 mM and 250 mM succinate buffers at pharmaceutically relevant freezing conditions. X-ray diffractometry studies revealed selective crystallization of monosodium succinate, which is posed as the causative mechanism. This salt crystallization was not observed in the presence of 2% w/v sucrose, suggesting that this pH shift can be mitigated by including sucrose in the formulation. Additionally, three monoclonal antibodies (mAbs) that represent different IgG subtypes and span a range of pIs (5.9 - 8.8) were formulated with succinate and sucrose and subjected to freeze-thaw, frozen storage and lyophilization. No detrimental impact on quality attributes (QA) such as high molecular weight (HMW) species, turbidity, alteration in protein concentration and sub-visible particles, was observed of any of the mAbs tested. Lastly, drug formulations lyophilized in succinate buffer with sucrose demonstrated acceptable QA profiles upon accelerated kinetic storage stability, supporting the use of succinate buffers in mAb drug products.     

Assays of physical stability and antioxidant activity of a topical formulation added with different plant extracts

In the present investigation the changes on physical stability (pH, viscosity, flow index and tixotropy) of topical formulations were evaluated following inclusion of different plant extracts containing flavonoids. Also, the antioxidant effect of these plant extracts alone and after addition in the formulation was evaluated using chemiluminescence and the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH(.-)) assays, as well as the inhibition of lipid peroxidation. Formulation added with dl-alpha-tocopherol was used to compare the physical stability and antioxidant activity. Formulations with plant extracts showed pseudoplastic behavior with decreasing on viscosity and tixotropy. The Glycyrrhiza glabra (GG) and Ginkgo biloba (GB) extracts alone and the formulations containing these extracts showed great antioxidant and free radical scavenging activities while the other extracts studied (mixture of Glycyrrhiza glabra, Symphytum officinale L and Arctium majus root, Nelumbium speciosum and soybean) showed lower activity. The results suggest that GG and GB extracts may be used in topical formulations in order to protect skin against damage caused by free radical and reactive oxygen species.     

Chemical stability of an ester prodrug of a glycoprotein IIb/IIIa receptor antagonist in solid dosage forms

DMP 754 is an ester prodrug of a glycoprotein IIb/IIIa receptor antagonist that undergoes ester and amidine hydrolysis in the presence of excipients. A means for the stabilization of DMP 754 was needed for the formulation of a stable drug product. Incorporation of a pH modifier in the formulation was used to control the microenvironment pH to coincide with that of maximum stability for DMP 754. Stability of tablets and capsules manufactured by (a) trituration process, (b) dry granulation process, and (c) wet granulation process was evaluated in HDPE bottles. Formulations manufactured by the dry and wet granulation processes contained disodium citrate as the pH modifier. Although aqueous wet granulation of a hydrolyzable drug is usually avoided, tablets and capsules manufactured by wet granulation were more stable in this case than those manufactured by the dry granulation process. This was attributed to the more uniform distribution of the pH modifier. Although the compression process resulted in enhanced degradation of the binary blend of DMP 754 and anhydrous lactose, tablets manufactured by the wet granulation process were more stable than capsules manufactured by the same process. Decreasing excipient-to-drug ratio enhanced the stability of tablets manufactured by the wet granulation process.