Effect of moisture sorption on the performance of crospovidone

Functionality of wet-granulated disintegrant in comparison to directly incorporated disintegrant in a poorly water-soluble tablet matrix

Tablet disintegration is crucial for drug release and subsequent systemic absorption. Although factors affecting the disintegrant's functionality have been extensively studied, the impact of wet granulation on the performance of disintegrants in a poorly water-soluble matrix has received much less attention. In this study, the disintegrants, crospovidone (XPVP), croscarmellose sodium (CCS) and sodium starch glycolate (SSG), were wet-granulated with dibasic calcium phosphate dihydrate as the poorly water-soluble matrix and polyvinylpyrrolidone as the binder. The effect of wet granulation was studied by evaluating tablet tensile strength and disintegratability. Comparison between tablets with granulated or ungranulated disintegrants as well those without disintegrants were also made. Different formulations showed different degrees of sensitivity to changes in tablet tensile strength and disintegratability post-wet granulation. Tablet tensile strength decreased for tablets with granulated disintegrant XPVP or CCS, but to a smaller extent for SSG. While tablets with granulated XPVP or CCS had increased disintegration time, the increment was lesser than for SSG, suggesting that wet granulation impacted a swelling disintegrant more. The findings showed that tablets with wet-granulated disintegrant had altered the disintegrant's functionality. These findings could provide better insights into changes in the disintegrant's functionality after wet granulation.

Development of a Swellable and Floating Gastroretentive Drug Delivery System (sfGRDDS) of Ciprofloxacin Hydrochloride

Sangelose^® (SGL) is a novel hydroxypropyl methylcellulose (HPMC) derivative that has been hydrophobically modified. Due to its high viscosity, SGL has the potential as a gel-forming and release-rate-controlled material for application in swellable and floating gastroretentive drug delivery systems (sfGRDDS). The aim of this study was to develop ciprofloxacin (CIP)-loaded sfGRDDS tablets comprised of SGL and HPMC in order to extend CIP exposure in the body and achieve optimal antibiotic treatment regimes. Results illustrated that SGL-HPMC-based sfGRDDS could swell to a diameter above 11 mm and showed a short floating lag time (<4 s) and long total floating time (>24 h) to prevent gastric emptying. In dissolution studies, CIP-loaded SGL-HPMC sfGRDDS demonstrated a specific biphasic release effect. Among the formulations, the SGL/type-K HPMC 15,000 cps (HPMC 15K) (50:50) group exhibited typical biphasic release profiles, with F4-CIP and F10-CIP individually releasing 72.36% and 64.14% CIP within 2 h dissolution, and sustaining release to 12 h. In pharmacokinetic studies, the SGL-HPMC-based sfGRDDS demonstrated higher C_max (1.56-1.73 fold) and shorter T_max (0.67 fold) than HPMC-based sfGRDDS. Furthermore, SGL 90L in GRDDS indicated an excellent biphasic release effect and a maximum elevation of relative bioavailability (3.87 fold). This study successfully combined SGL and HPMC to manufacture sfGRDDS that retain CIP in the stomach for an optimal duration while improving its pharmacokinetic characteristics. It was concluded that the SGL-HPMC-based sfGRDDS is a promising biphasic antibiotic delivery system that can both rapidly achieve the therapeutic antibiotic concentration and maintain the plasma antibiotic concentration for an extended period to maximize antibiotic exposure in the body.

Relative Humidity Cycling: Implications on the Stability of Moisture-Sensitive Drugs in Solid Pharmaceutical Products

The stability of a moisture-sensitive drug in tablet formulations depends particularly on the environment's relative humidity (RH) and the products' prior exposure to moisture. This study was designed to understand drug stability in relation to the moisture interaction of the excipients, moisture history of the tablets, and RH of the environment. The stability study was performed on tablets containing acetylsalicylic acid (ASA), formulated with common pharmaceutical excipients like native maize starch, microcrystalline cellulose (MCC), partially pregelatinized maize starch (PGS), dicalcium phosphate dihydrate (DCP), lactose, and mannitol. The tablets were subjected to storage conditions with RH cycling alternating between 53% and 75%. Results were also compared to tablets stored at a constant RH of 53% or 75%. The excipients demonstrated marked differences in their interactions with moisture. They could be broadly grouped as excipients with RH-dependent moisture content (native maize starch, MCC, and PGS) and RH-independent moisture content (DCP, lactose, and mannitol). As each excipient interacted differently with moisture, degradation of ASA in the tablets depended on the excipients' ability to modulate the moisture availability for degradation. The lowest ASA degradation was observed in tablets formulated with low moisture content water-soluble excipients, such as lactose and mannitol. The impact of RH cycling on ASA stability was apparent in tablets containing native maize starch, MCC, PGS, or DCP. These findings suggested that the choice of excipients influences the effect of moisture history on drug stability. The results from studies investigating moisture interaction of excipients and drug stability are valuable to understanding the inter-relationship between excipients, moisture history, and drug stability.

Tablet Disintegratability: Sensitivity of Superdisintegrants to Temperature and Compaction Pressure

Tablet disintegration is an important pre-requisite for drug dissolution and absorption. The disintegration test is typically conducted at 37 °C, but the intragastric temperature may vary due to meals or fever. This study investigated the effects of temperature and compaction pressure on tablet disintegratability to gain deeper insights into superdisintegrant sensitivity and function. Tablets with either sodium starch glycolate or crospovidone as disintegrant were prepared at various compaction pressures and subjected to the disintegration test using different medium temperatures. Preheating of tablets was also employed to establish instant temperature equilibrium between the tablet and the disintegration medium. Liquid penetration and disintegration were faster as the medium temperature increased or compaction pressure decreased. Swelling or strain recovery disintegrants exhibited similar sensitivity to variations in the medium temperature. Preheating of the tablets resulted in slower disintegration, but this effect was reversible upon cooling, hence the slower disintegration was unlikely to be attributed to changes in the disintegrant physical state. The temperature difference between the tablet and the disintegration medium likely affected the rate of fluid flow into tablets and influenced disintegration. Understanding disintegrant temperature sensitivity would help to avoid unacceptable fluctuations in disintegration due to temperature variations. The temperature difference effect could also be harnessed to boost disintegrant performance.

Investigating the role of excipients on the physical stability of directly compressed tablets

Stability studies are an integral part of the drug development process for any drug product. In addition to monitoring chemical degradation, the physical stability of a drug product must also be evaluated to ensure that the drug release and performance is not affected by storage. In this study, directly compressed tablets of 16 different formulations were exposed to an accelerated stability program to quantify changes in tablet breaking force, porosity, contact angle and disintegration time. Tablets were exposed to five different storage conditions from 37∘ C/30% relative humidity (RH) to 70∘ C/75%RH with testing after 2 and 4 weeks of storage. Each formulation contained two different fillers (47% w/w each), a disintegrant (5% w/w) and magnesium stearate (1% w/w). The results show that tablets stored at high humidity show increases in porosity and decreases in tensile strength, particularly if they contain a highly hygroscopic filler such as microcrystalline cellulose (MCC). For tablets stored at high temperature, the most commonly affected property was the tablet wettability, measured by sessile drop contact angle measurements. These results are considered in combination with the performance-controlling disintegration mechanism (Maclean et al., 2021) to identify the critical properties which influence the performance after storage.

Impact of Amylose-Amylopectin Ratio of Starches on the Mechanical Strength and Stability of Acetylsalicylic Acid Tablets

The two main components of starch - amylose and amylopectin, are responsible for its interaction with moisture. This study investigated how moisture sorption properties of the starches with different amylose-amylopectin ratio impacted tablet properties including drug stability. The starch samples were equilibrated to 33, 53, and 75% relative humidity (RH) and then assessed for tabletability, compactibility, and yield pressure. Effect of humidity on viscoelastic recovery was also evaluated. Tabletability and compactibility of high-amylose starch were better than that of high-amylopectin starch at 33 and 53% RH. However, at 75% RH, the reverse was observed. In terms of yield pressure, high-amylose starch had lower yield pressure than high-amylopectin starch. High-amylose starch tablets also exhibited lower extent of viscoelastic recovery than high-amylopectin starch tablets. The variations in the tableting properties were found to be related to relative locality of the sorbed moisture. Degradation of acetylsalicylic acid in high-amylose starch tablets at 75% RH, 40°C was less than the tablets with high-amylopectin starch. This observation could be attributed to the greater amount of water molecules binding sites in high-amylose starch. Furthermore, most of the sorbed moisture of high-amylose starch was internally absorbed moisture, therefore limiting the availability of diffusible sorbed moisture for degradation reaction. Findings from this study could provide better insights on the influence of amylose-amylopectin ratio on tableting properties and stability of moisture-sensitive drugs. This is of particular importance as starch is a common excipient in solid dosage forms.

Time-domain NMR analysis for the determination of water content in pharmaceutical ingredients and wet granules

The application of time-domain NMR (TD-NMR) analysis to quantify water content in pharmaceutical ingredients is demonstrated. The initial phase of the study employed a range of disintegrants with defined amounts of added water (0-30% of the total weight) as samples; the disintegrants included croscarmellose sodium, corn starch, low-substituted hydroxypropyl cellulose, and crospovidone. After acquisition of the T₂ relaxation curves of the samples by TD-NMR measurements, these curves were analyzed by partial least squares (PLS) regression. According to the analysis, accurate and reliable PLS models were created that enabled accurate assessment of water content in the samples. A powder blend consisting of acetaminophen (paracetamol) and tablet excipients was also examined. Both a physical mixture of the powder blend and a wet granule prepared with a high-speed granulator were tested as samples in this study. Precise determination of water content in the powder blend was achieved by using the TD-NMR method. The accuracy of water content determination was equivalent to or better than that of the conventional loss on drying method. TD-NMR analysis samples were measured nondestructively and rapidly with low cost; thus, it could be a powerful quantitative method for determining water content in pharmaceuticals.

Investigation on the impact of different proportions of components in formulations on stability of a moisture sensitive drug

Physicochemical and mechanical properties of tablets are largely dictated by formulation compositions. Different excipients possess different tableting and moisture sorption behaviors. Therefore, this study was designed to elucidate the relative influence of the proportion of components in formulations on tablet properties. Acetylsalicylic acid (ASA) tablets containing different proportions of starch, microcrystalline cellulose (MCC) and calcium hydrogen phosphate dihydrate (DCP) were prepared. The excipients were evaluated for their moisture sorption properties. Mechanical strength of the tablets was determined alongside with ASA stability, by storing the tablets at 75% RH, 25 °C. The stability study showed the importance of drug loading level on its stability. For a fixed ASA proportion, formulations with more starch were able to absorb more moisture and possessed larger areas of hysteresis loop in their moisture sorption isotherms. The presence of starch contributed positively to ASA stability although increasing proportions of starch compromised the tablet mechanical properties. Contrastingly, MCC produced mechanically stronger tablets as its plastically deforming and fibrous properties contributed to a good structural network. The findings provide a deeper understanding of the dichotomous effect by the proportion of components in formulations containing a moisture sensitive drug on drug stability and mechanical strength of the resultant tablets.

Effect of Pharmaceutical Excipients on Intestinal Absorption of Metformin via Organic Cation-Selective Transporters

Growing evidence has shown that some pharmaceutical excipients can act on drug transporters. The present study was aimed at investigating the effects of 13 commonly used excipients on the intestinal absorption of metformin (MTF) and the underlying mechanisms using Caco-2 cells and an ex vivo mouse non-everted gut sac model. First, the uptake of MTF in Caco-2 cells was markedly inhibited by nonionic excipients including Solutol HS 15, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 80, and crospovidone. Second, transport profile studies showed that MTF was taken up via multiple cation-selective transporters, among which a novel pyrilamine-sensitive proton-coupled organic cation (H⁺/OC⁺) antiporter played a key role. Third, Solutol HS 15, polysorbate 40, and polysorbate 60 showed cis-inhibitory effects on the uptake of either pyrilamine (prototypical substrate of the pyrilamine-sensitive H⁺/OC⁺ antiporter) or 1-methyl-4-phenylpyridinium (substrate of traditional cation-selective transporters including OCTs, MATEs, PMAT, SERT, and THTR-2), indicating that their suppression on MTF uptake is due to the synergistic inhibition toward multiple influx transporters. Finally, the pH-dependent mouse intestinal absorption of MTF was significantly decreased by Solutol HS 15, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 80, and pyrilamine. In conclusion, this study revealed that a novel transport process mediated by the pyrilamine-sensitive H⁺/OC⁺ antiporter contributes to the intestinal absorption of MTF in conjunction with the traditional cation-selective transporters. Mechanistic understanding of the interaction of excipients with cation-selective transporters can improve the formulation design and clinical application of cationic drugs.

Advancing the understanding of the tablet disintegration phenomenon - An update on recent studies

Disintegration is the de-aggregation of particles within tablets upon exposure to aqueous fluids. Being an essential step in the bioavailability cascade, disintegration is a fundamental quality attribute of immediate release tablets. Although the disintegration phenomenon has been studied for over six decades, some gaps of knowledge and research questions still exist. Three reviews, published in 2015, 2016 and 2017, have discussed the literature relative to tablet disintegration and summarised the understanding of this topic. Yet, since then more studies have been published, adding to the established body of knowledge. This article guides a step forward towards the comprehension of disintegration by reviewing, concisely, the most recent scientific updates on this topic. Initially, we revisit the mechanisms of disintegration with relation to the three most used superdisintegrants, namely sodium starch glycolate, croscarmellose sodium and crospovidone. Then, the influence of formulation, storage, manufacturing and media conditions on disintegration is analysed. This is followed by an excursus on novel disintegrants. Finally, we highlight unanswered research questions and envision future research venues in the field.

From the laboratory to the end-user: a primary packaging study for microneedle patches containing amoxicillin sodium

Abstract

As microneedle (MN) patches progress towards commercialisation, there is a need to address issues surrounding their translation from the laboratory to the end-user. One important aspect of MN patches moving forward is appropriate primary packaging. This research focuses on MN patches containing amoxicillin (AMX) sodium for the potential treatment of neonatal sepsis in hot and humid countries. A MN patch consists of a hydrogel-forming MN array and a drug-containing reservoir. Improper primary packaging in hot and humid countries may result in degradation of active pharmaceutical ingredients, with the use of substandard medicines a major health concern. The research presented here, for the first time, seeks to investigate the integrity of MN patches in different primary packaging when stored under accelerated storage conditions, according to international guidelines. At pre-defined intervals, the performance of the MN patch was investigated. Major causes of drug instability are moisture and temperature. To avoid unnecessary degradation, suitable primary packaging was sought. After 168 days, the percentage of AMX sodium recovered from drug-containing reservoirs packaged in Protect™ 470 foil was 103.51 ± 7.03%. However, packaged in poly(ester) foil, the AMX sodium content decreased significantly (p = 0.0286), which is likely due to the degradation of AMX sodium by the imbibed moisture. Therefore, convincing evidence was provided as to the importance of investigating the stability of MN patches in primary packaging intended for MN-mediated transdermal delivery so that they are ‘fit for purpose’ when it reaches the end-user. Future work will include qualitative studies to assess MN patch usability.

Graphical abstract

Insights into the Moisture Scavenging Properties of Different Types of Starch in Tablets Containing a Moisture-Sensitive Drug

Starch is a commonly used excipient in the pharmaceutical industry. However, information on the effect of the moisture scavenging properties of starch to protect moisture-sensitive drugs is limited. The interaction between starch and moisture is of particular interest as moisture fugacity can impact drug stability. In this study, the moisture behavior of different starches was examined for an understanding of its role in the degradation of acetylsalicylic acid. The starches were characterized for their dimensional- and moisture-related properties. Stability testing was carried out on tablets containing acetylsalicylic acid and different starches. Although moisture sorption processes were visually comparable for the different starches, quantitative differences were found in their moisture interaction and distribution. From the sorption isotherms, moisture monolayer coverage and area of hysteresis were found to correlate well with the percentage of acetylsalicylic acid degradation. The lowest percentage of acetylsalicylic acid degradation was observed in starch that exhibited high monolayer coverage, large area of hysteresis, and good capacity for internally absorbed moisture. Findings from this study highlighted the value of moisture scavenging excipients when formulating moisture-sensitive drug products. Clearly, the assessment of moisture sorption properties of excipients during the preformulation phase can be an invaluable exercise for identifying the best possible ingredients in formulations where moisture sensitivity is an area of concern.

Disintegrant Selection in Hydrophobic Tablet Formulations

The hydrophobicity of poorly soluble drugs can delay tablets disintegration. We probed here the influence of different disintegrants on the disintegration of challenging hydrophobic formulations. Tablets containing diluents, hydrogenated vegetable oil and either sodium starch glycolate (SSG), croscarmellose sodium (CCS) or crospovidone (XPVP) were prepared. The disintegration time of tablets was tested immediately and after storage at 40 °C and 75% RH in sealed bags. Results show that storage and compression force had a negative effect on disintegration, particularly with 1% disintegrant. The performance of the three disintegrants was in the following order: CCS (best) > SSG > XPVP. For example, tablets containing 1% CCS, SSG and XPVP, compressed at 20 kN, disintegrated in ≈3, ≈12 and ≈69 min, respectively, after two months storage. Settling volume, liquid uptake and effect of storage on physical properties of the pure disintegrants were also studied and revealed that the reduced performance of XPVP is related to: 1) its rapid, yet short-range expansion upon liquid exposure and 2) its change of behaviour on storage. In conclusion, CCS ensured rapid disintegration at low concentration across various compression forces and storage times. Thus, the use of CCS in hydrophobic tablet formulations is recommended.

A study of the impact of excipient shielding on initial drug release using UV imaging

Knowledge on the dissolution behaviour of a drug is critical for efficient and effective product development. As the drug has almost always to be formulated with excipients in the design of a dosage form, it is important to examine the implications of the choice of excipients on the dissolution of the drug, among others, especially in the case of an immediate release dosage form. The objective of this study was to explore the potential of using an ultraviolet (UV) imaging technique to examine the effect of drug-excipient ratio on the initial dissolution of the drug, when formulated with a hydrophilic, water insoluble excipient. A series of drug-excipient binary blends with different ratios were prepared and compacted into 2 mm compacts, and their dissolution profiles captured with a UV imager. Chemical imaging via Raman spectroscopy was also performed on the compacts to quantify the fraction of drug presented on the compact surface. At low drug concentrations, a suppression in drug dissolution was observed, but beyond a critical drug-excipient ratio, the concentration of the excipient no longer played a role in affecting drug dissolution rates. Drug particle size was found to affect the critical drug-excipient ratio required to negate the shielding effect exerted by the excipient, such that a higher proportion of drug was required. It is postulated that the excipient served as a physical barrier, as well as competitor for water required for wetting during initial dissolution, thereby causing a delay in the wetting and dissolution of the drug.