Dissolution and solid-state characterization of poorly water-soluble drugs in the presence of a hydrophilic carrier

Advances in the development of amorphous solid dispersions: The role of polymeric carriers

Amorphous solid dispersion (ASD) is one of the most effective approaches for delivering poorly soluble drugs. In ASDs, polymeric materials serve as the carriers in which the drugs are dispersed at the molecular level. To prepare the solid dispersions, there are many polymers with various physicochemical and thermochemical characteristics available for use in ASD formulations. Polymer selection is of great importance because it influences the stability, solubility and dissolution rates, manufacturing process, and bioavailability of the ASD. This review article provides a comprehensive overview of ASDs from the perspectives of physicochemical characteristics of polymers, formulation designs and preparation methods. Furthermore, considerations of safety and regulatory requirements along with the studies recommended for characterizing and evaluating polymeric carriers are briefly discussed.

Variability in the substitution pattern of hydroxypropyl cellulose affects its physico-chemical properties

Hydroxypropyl cellulose (HPC) is a water-soluble polymer with many applications in food, pharmaceutical, medical, or paints industries. Past studies have reported that differences in functionality can occur between products of similar pharmaceutical grades. Understanding the origin of these differences is a major challenge for the industry. In this work, the structure and physico-chemical properties of several HPC samples of the same commercial grade were studied. Structural analysis by NMR and enzymatic hydrolysis were performed to study molar substitution and distribution of substituents along the polymer chain respectively. Water-polymer interactions, surface properties as well as rheological and thermal behavior were characterized to tentatively correlate them with the structure, and gain new insights into the structure-function relationship of this polymer. The differences in structure revealed between the samples affect their properties. The unexpected behavior of one sample was attributed to a more heterogeneous substitution pattern, with the coexistence of highly and weakly substituted regions along the same polymer chain. The more block-like distribution of substituents has a great effect on the clouding behavior and surface tension reduction ability of the polymer.

A Full Factorial Design to Optimize Aminexil Nano Lipid Formulation to Improve Skin Permeation and Efficacy Against Alopecia

Aminexil (AMX) is considered to be one of the most widely used hair growth promoters. Nanostructured lipid carriers (NLC) are employed to increase the permeation of both lipophilic and hydrophilic drugs. Aminexil nanostructured lipid carrier (NLC) designed by pre-emulsion/ultrasonication method was utilized for alopecia treatment. For selecting optimum excipients, a solubility study was executed in liquid lipids, solid lipids, surfactants, and co-surfactants. A 2³ full factorial design was utilized for NLC optimization. Characterization of the developed formulas was performed. The penetration of the optimized formula across cuticle tissues was studied using confocal laser scanning microscopy (CLSM). AMX showed high solubility in glyceryl monostearate (GMS) and stearic acid, 28.87 ± 2.17 and 58.06 ± 2.227 mg/g, respectively. The results of physicochemical characterization showed that formula A7 was the optimized one. It is composed of GMS (solid lipid), oleic acid:garlic oil (1:1 v/v) (liquid lipid), and a surfactant/co-surfactant mixture (Cremophor EL/Transcutol HP). The particle size (PS) was 238.0 ± 2.13 nm, entrapment efficiency (EE) 100.535 ± 6.73%, and zeta potential (ZP) - 29.3 ± 0.93 mv. Ex vivo permeation study demonstrates the potential of AMX-NLC (formula A7) as a delivery system for AMX. The CLSM highly proved AMX-loaded NLC penetration through the skin. The histological study clearly demonstrated that AMX-loaded NLC promoted hair growth more effectively than the market product in chemotherapy-induced alopecia rats. The acquired findings revealed that targeting of AMX-loaded NLC into hair follicles was improved.

Elucidating the Impact of Surfactants on the Performance of Dissolving Microneedle Array Patches

The need for biocompatible polymers capable of dissolving in the skin while exhibiting reasonable mechanical features and delivery efficiency limits the range of materials that could be utilized in fabricating dissolving microneedle array patches (MAPs). The incorporation of additives, such as surfactants, during microneedle fabrication might be an alternative solution to overcome the limited range of materials used in fabricating dissolving MAPs. However, there is a lacuna in the knowledge on the effect of surfactants on the manufacture and performance of dissolving MAPs. The current study explores the role of surfactants in the manufacture and performance of dissolving MAPs fabricated from poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) loaded with the model drugs, ibuprofen sodium and itraconazole. Three nonionic surfactants, Lutrol F108, Pluronic F88, and Tween 80, in solutions at varying concentrations (0.5, 1.0, and 2.0% w/w) were loaded into these dissolving MAPs. It was discovered that all of the dissolving MAPs that incorporated surfactant displayed a lower reduction in the microneedle height (≈10%) relative to the control formulation (≈20%) when subjected to a compressive force of 32 N. In addition, the incorporation of surfactants in some instances enhanced the insertion profile of these polymeric MAPs when evaluated using ex vivo neonatal porcine skin. The incorporation of surfactant into ibuprofen sodium-loaded dissolving MAPs improved the insertion depth of MAPs from 400 μm down to 600 μm. However, such enhancement was not apparent when the MAPs were loaded with the model hydrophobic drug, itraconazole. Skin deposition studies highlighted that the incorporation of surfactant enhanced the delivery efficiency of both model drugs, ibuprofen sodium and itraconazole. The incorporation of surfactant enhanced the amount of ibuprofen sodium delivered from 60.61% up to ≈75% with a majority of the drug being delivered across the skin and into the receptor compartment. On the other hand, when surfactants were added into MAPs loaded with the model hydrophobic drug itraconazole, we observed enhancement in intradermal delivery efficiency from 20% up to 30%, although this did not improve the delivery of the drug across the skin. This work highlights that the addition of nonionic surfactant is an alternative formulation strategy worth exploring to improve the performance and delivery efficiency of dissolving MAPs.

Supersaturated formulations of poorly soluble weak acid drugs evaluated in rodents; a case study

In the present study we describe a way of working to overcome oral administration challenges in an early preclinical project. As candidate drugs were obtained, the preclinical delivery route was replaced by the intended route of the product and resources were allocated to optimize the oral absorption. Two main approaches were followed in order to formulate a selected weak acid, AZ'403, for oral administration in large scale toxicological studies and the early clinical phases. Both approaches relies on the suppression of precipitation from obtained supersaturated solutions achieved either by amorphous solid dispersions (using hydroxypropyl methylcellulose acetate succinate, HPMC-AS) or crystalline salts (sodium and potassium salts). In vivo studies in rodents were performed to evaluate oral AZ'403 absorption from amorphous and crystalline formulations, using nano- and micro crystalline particles of the neutral form, as references. The oral absorption of AZ'403 formulated using both approaches was significantly higher compared with the references. The improvements in overall exposures were 7-100 times during the investigated conditions. The pharmacokinetic profiles implied that both solid dispersions and crystalline salts of AZ'403 generated supersaturation in the small intestine in rodents and indicated that both approaches may be ways forward for subsequent late stage product development.

Enhanced solubility and biopharmaceutical performance of atorvastatin and metformin via electrospun polyvinylpyrrolidone-hyaluronic acid composite nanoparticles

The study was aimed to improve the aqueous solubility of atorvastatin (AT) and ameliorate permeability of metformin (MT) in a combination formulation, improving their oral bioavailability. Several AT-MT loaded polyvinylpyrrolidone (PVP) and hyaluronic acid (HA) based nanoparticles were prepared through electrospraying method (ES-NPs), and tested for physicochemical, in vitro, and in vivo parameters. Among the trialed formulations, a sample consisting of AT, MT, PVP, and HA at the weight ratio of 1/6.25/3.75/15 furnished the most satisfying solubility and release rate results. It enhanced approximately 10.3-fold and 3.6-fold solubility of AT as compared with AT powder and marketed product (Lipilow) in phosphate buffer pH = 6.8, respectively. Whereas, permeation of MT was 1.60-fold and 1.47-fold improved as compared with MT powder and marketed product (Glucophage), respectively. As compared with Lipilow, AUC _(0-∞) and C_max of AT with ES-NPs in rats were improved to 3.6-fold and 3.2-fold, respectively. Similarly, as compared with Glucophage, AUC _(0-∞) and C_max of MT were improved to 2.3-fold and 1.8-fold, respectively. Thus, ES-NPs significantly enhanced the solubility of AT (a BCS class II drug) and permeability of MT (a BCS class III drug) and might be a promising drug delivery system for co-delivery of these drugs.

Influence of high pressure compaction on solubility and intrinsic dissolution of ibuprofen binary mixtures employing standard excipients

Enabling formulations often depend on functional excipients. However, the question remains whether excipients regarded as standard establish similar interactions and subsequently improvement of solubility when employed at unusual manufacturing process conditions. In this study, compaction of API under high pressure in the presence of hydrophilic excipients is proposed as a technique to improve the solubility and/or dissolution rate with an acceptable preservation of the supersaturation state. Binary mixtures of ibuprofen (IBU) with hydroxypropyl cellulose, isomalt, mannitol and sorbitol were compacted applying high pressure (500 MPa) with and without a previous co-milling step. Intrinsic dissolution rate (IDR) was selected to characterize and evaluate dissolution performance. The IDR of neat IBU increased from 5 to 88 fold and the aqueous solubility in the range of 3 to 54%. Regarding the polyols isomalt showed the highest impact on solubility and dissolution, without changing the crystallinity of IBU independent of a co-milling step. Even higher impact was achieved in combination with HPC. However, only without a previous co-milling step, ibuprofen remained crystalline, while co-milling induced an amorphous IBU-content of 38%. Based on XRPD and DSC findings, higher IDR and solubility values correlated with crystal modifications as well as IBU/excipient interactions.

Influence of Polyvinyl Alcohol (PVA) on PVA-Poly-N-hydroxyethyl-aspartamide (PVA-PHEA) Microcrystalline Solid Dispersion Films

This study was conducted to formulate buccal films consisting of polyvinyl alcohol (PVA) and poly-N-hydroxyethyl-aspartamide (PHEA), to improve the dissolution of the drug through the oral mucosa. Ibuprofen sodium salt was used as a model drug, and the buccal film was expected to enhance its dissolution rate. Two different concentrations of PVA (5% w/v and 7.5% w/v) were used. Solvent casting was used to prepare films, where a solution consisting of drug and polymer was cast and allowed to dry. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to investigate the properties of films. In vitro dissolution studies were also conducted to investigate drug release. SEM studies showed that films containing a higher concentration of PVA had larger particles in microrange. FTIR studies confirmed the presence of the drug in films and indicated that ibuprofen sodium did not react with polymers. DSC studies confirmed the crystalline form of ibuprofen sodium when incorporated within films. In vitro dissolution studies found that the dissolution percentage of ibuprofen sodium alone was increased when incorporated within the film from 59 to 74%. This study led to the development of solid microcrystalline dispersion as a buccal film with a faster dissolution rate than the drug alone overcoming problem of poor solubility.

Bioavailability Enhancement of Poorly Water-Soluble Drugs via Nanocomposites: Formulation⁻Processing Aspects and Challenges

Drug nanoparticles embedded in a dispersant matrix as a secondary phase, i.e., drug-laden nanocomposites, offer a versatile delivery platform for enhancing the dissolution rate and bioavailability of poorly water-soluble drugs. Drug nanoparticles are prepared by top-down, bottom-up, or combinative approaches in the form of nanosuspensions, which are subsequently dried to prepare drug-laden nanocomposites. In this comprehensive review paper, the term “nanocomposites” is used in a broad context to cover drug nanoparticle-laden intermediate products in the form of powders, cakes, and extrudates, which can be incorporated into final oral solid dosages via standard pharmaceutical unit operations, as well as drug nanoparticle-laden strip films. The objective of this paper is to review studies from 2012⁻2017 in the field of drug-laden nanocomposites. After a brief overview of the various approaches used for preparing drug nanoparticles, the review covers drying processes and dispersant formulations used for the production of drug-laden nanocomposites, as well as various characterization methods including quiescent and agitated redispersion tests. Traditional dispersants such as soluble polymers, surfactants, other water-soluble dispersants, and water-insoluble dispersants, as well as novel dispersants such as wet-milled superdisintegrants, are covered. They exhibit various functionalities such as drug nanoparticle stabilization, mitigation of aggregation, formation of nanocomposite matrix⁻film, wettability enhancement, and matrix erosion/disintegration. Major challenges such as nanoparticle aggregation and poor redispersibility that cause inferior dissolution performance of the drug-laden nanocomposites are highlighted. Literature data are analyzed in terms of usage frequency of various drying processes and dispersant classes. We provide some engineering considerations in comparing drying processes, which could account for some of the diverging trends in academia vs. industrial practice. Overall, this review provides rationale and guidance for drying process selection and robust nanocomposite formulation development, with insights into the roles of various classes of dispersants.

Preparation of Nanoparticles Including Antisolvent Drugs by the Combination of Roll Milling and High-pressure Homogenization

DESCRIPTION

Design methods of nanoparticle formulations are divided into break-down methods and build-up methods. The former is further divided into dry and wet processes. For drug nanoparticle preparations, the wet process is generally employed, and organic solvents are used in most formulations.

METHOD

In this study, we investigate the preparation of nifedipine (IB) and griseofulvin (GF) nanoparticles without using organic solvent. Both IB and GF nanoparticles, with a mean particle size of approximately 50 nm, were prepared without organic solvent by employing a combination of roll milling and high-pressure homogenization.

RESULT

The X-ray diffraction peak of the IB and GF samples prepared by roll milling was present at a position (2θ) identical to that of IB and GF crystals, indicating that no peak shift was induced by interaction with phospholipids.

CONCLUSION

These findings demonstrate that most IB and GF nanoparticles exist as crystals in phospholipids.

In vitro and in vivo investigation of the gastrointestinal behavior of simvastatin

Simvastatin (SV) is marketed as a lactone ester prodrug which is hydrolyzed to the active simvastatin hydroxyacid (SVA). SV is characterized by a low solubility and undergoes extensive first-pass metabolism. In this study, the influence of the upper gastrointestinal environment on the intraluminal behavior of simvastatin was investigated by a series of in vitro experiments. Dissolution, stability and two-stage dissolution tests were performed using simulated and human gastrointestinal fluids. The dissolution studies revealed a relatively slow dissolution of SV as well as conversion of SV to SVA. The hydrolysis of SV was further examined and stability studies indicated a faster conversion in gastric fluids than in intestinal fluids. These isolated phenomena were then confirmed by the more integrative two-stage dissolution studies. To estimate the predictive value of the in vitro tests, an additional in vivo study was performed in which the gastrointestinal concentration-time profiles also revealed a slow dissolution of SV and faster degradation of SV to SVA in the stomach than in the intestinal tract. However, the plasma concentrations of SV and SVA did not directly correlate with the observed gastrointestinal concentrations, suggesting that gut wall and hepatic metabolism have a greater impact on systemic exposure of SV than the intraluminal interconversion between SV and SVA.

Deposition of Ibuprofen Crystals on Hydroxypropyl Cellulose/Polyacrylamide Gel: Experimental and Mathematic Modeling Releasing

The crystallization of nonsteroidal anti-inflammatory drug [2-(4-isobutyl-phenyl) propionic acid] ibuprofen (IBP) on a hydroxypropyl cellulose (HPC) and polyacrylamide (PAAm) gel was studied as well as the release kinetics of the drug. The IBP was crystallized on the gel surface of HPC/PAAm. It had a prismatic shape and the growth was made in an aqueous medium; the crystallinity grade of the gels HPC/PAAm and HPC/PAAm-IBU increased to 68% and to 58%, respectively. The release of IBP is performed by two means: by a non-Fickian diffusion process and by relaxation of the chains of the gel; without regard to temperature and the diffusion media, this correlates with the lower critical solution temperature (LCST) of the proposed gel. This polymer matrix provides an option for releasing nonsteroidal anti-inflammatory drugs in a temperature range of 35–39°C. Korsmeyer and Peppas mathematical model was simulated for data releases, statistically significant at 95% confidence level.

Topical cream-based dosage forms of the macrocyclic drug delivery vehicle cucurbit[6]uril

The macrocycle family of molecules called cucurbit[n]urils are potential drug delivery vehicles as they are able to form host-guest complexes with many different classes of drugs. This study aimed to examine the utility of Cucurbit[6]uril (CB[6]) in topical cream-based formulations for either localised treatment or for transdermal delivery. Cucurbit[6]uril was formulated into both buffered cream aqueous- and oily cream-based dosage forms. The solid state interaction of CB[6] with other excipients was studied by differential scanning calorimetry and the macrocycle's transdermal permeability was determined using rat skin. Significant solid state interactions were observed between CB[6] and the other dosage form excipients. At concentrations up to 32% w/w the buffered aqueous cream maintained its normal consistency and could be effectively applied to skin, but the oily cream was too stiff and is not suitable as a dosage form. Cucurbit[6]uril does not permeate through skin; as such, the results imply that cucurbituril-based topical creams may potentially only have applications for localised skin treatment and not for transdermal drug delivery.

Improvement of Physico-mechanical Properties of Partially Amorphous Acetaminophen Developed from Hydroalcoholic Solution Using Spray Drying Technique

OBJECTIVE(S)

This study was performed aiming to investigate the effect of particle engineering via spray drying of hydroalcoholic solution on solid states and physico-mechanical properties of acetaminophen.

MATERIALS AND METHODS

Spray drying of hydroalcoholic solution (25% v/v ethanol/water) of acetaminophen (5% w/v) in the presence of small amounts of polyninylpyrrolidone K30 (PVP) (0, 1.25, 2.5 and 5% w/w based on acetaminophen weight) was carried out. The properties of spray dried particles namely morphology, surface characteristics, particle size, crystallinity, dissolution rate and compactibility were evaluated.

RESULTS

Spray drying process significantly changed the morphology of acetaminophen crystals from acicular (rod shape) to spherical microparticle. Differential scanning calorimetery (DSC) and x-ray powder diffraction (XRPD) studies ruled out any polymorphism in spray dried samples, however, a major reduction in crystallinity up to 65%, especially for those containing 5% w/w PVP was observed. Spray dried acetaminophen particles especially those obtained in the presence of PVP exhibited an obvious improvement of the dissolution and compaction properties. Tablets produced from spray dried samples exhibited excellent crushing strengths and no tendency to cap.

CONCLUSIONS

The findings of this study revealed that spray drying of acetaminophen from hydroalcoholic solution in the presence of small amount of PVP produced partially amorphous particles with improved dissolution and excellent compaction properties.