Phenazopyridine-phthalimide nano-cocrystal: Release rate and oral bioavailability enhancement

A SWOT analysis of nano co-crystals in drug delivery: present outlook and future perspectives

The formulation of poorly soluble drugs is an intractable challenge in the field of drug design, development and delivery. This is particularly problematic for molecules that exhibit poor solubility in both organic and aqueous media. Usually, this is difficult to resolve using conventional formulation strategies and has resulted in many potential drug candidates not progressing beyond early stage development. Furthermore, some drug candidates are abandoned due to toxicity or have an undesirable biopharmaceutical profile. In many instances drug candidates do not exhibit desirable processing characteristics to be manufactured at scale. Nanocrystals and co-crystals, are progressive approaches in crystal engineering that can solve some of these limitations. While these techniques are relatively facile, they also require optimisation. Combining crystallography with nanoscience can yield nano co-crystals that feature the benefits of both fields, resulting in additive or synergistic effects to drug discovery and development. Nano co-crystals as drug delivery systems can potentially improve drug bioavailability and reduce the side-effects and pill burden of many drug candidates that require chronic dosing as part of treatment regimens. In addition, nano co-crystals are carrier-free colloidal drug delivery systems with particle sizes ranging between 100 and 1000 nm comprising a drug molecule, a co-former and a viable drug delivery strategy for poorly soluble drugs. They are simple to prepare and have broad applicability. In this article, the strengths, weaknesses, opportunities and threats to the use of nano co-crystals are reviewed and a concise incursion into the salient aspects of nano co-crystals is undertaken.

Skin ulcers as a complication of short-term use of phenazopyridine in an old man: A case report

INTRODUCTION

Phenazopyridine is an azo dye, which exerts local anesthetic or analgesic action on urinary tract mucosa through an unknown mechanism. Besides its common complications including orange discoloration of the urine and gastrointestinal problems, it may have rare side effects like hemolytic anaemia, methemoglobinemia, renal failure, and skin changes. We reported a paraplegic man with skin ulcers on scretom and right foot after about 3 days of phenazopyridine use CASE REPORT: A 62-year-old man presented with flesh shaped deep ulcers in lower parts of the body. He declared that at first a bluish discoloration was developed in the lower extremities and scrotum skin after use of eight phenazopyridine tablets (200 mg) and then these lesions turned to blisters and ulcers and they were prurient. The patient underwent sonography and CT-angiography; however, no pathologic findings were found. He just received losartan for many years as past drug history. According to the history, a delayed drug hypersensitivity reaction was suspected and the patient wounds healed after using special type of dressings and antibiotic therapy regarding positive wound cultures.

CONCLUSION

Phenazopyridine severe skin changes are hardly reported. We described a case who experienced severe skin reactions and ulcers following phenazopyridine use not related to other complications including renal dysfunction, methemoglobinemia, and hemolytic anemia.

Crystal Engineering of Pharmaceutical Cocrystals in the Discovery and Development of Improved Drugs

The subject of crystal engineering started in the 1970s with the study of topochemical reactions in the solid state. A broad chemical definition of crystal engineering was published in 1989, and the supramolecular synthon concept was proposed in 1995 followed by heterosynthons and their potential applications for the design of pharmaceutical cocrystals in 2004. This review traces the development of supramolecular synthons as robust and recurring hydrogen bond patterns for the design and construction of supramolecular architectures, notably, pharmaceutical cocrystals beginning in the early 2000s to the present time. The ability of a cocrystal between an active pharmaceutical ingredient (API) and a pharmaceutically acceptable coformer to systematically tune the physicochemical properties of a drug (i.e., solubility, permeability, hydration, color, compaction, tableting, bioavailability) without changing its molecular structure is the hallmark of the pharmaceutical cocrystals platform, as a bridge between drug discovery and pharmaceutical development. With the design of cocrystals via heterosynthons and prototype case studies to improve drug solubility in place (2000-2015), the period between 2015 to the present time has witnessed the launch of several salt-cocrystal drugs with improved efficacy and high bioavailability. This review on the design, synthesis, and applications of pharmaceutical cocrystals to afford improved drug products and drug substances will interest researchers in crystal engineering, supramolecular chemistry, medicinal chemistry, process development, and pharmaceutical and materials sciences. The scale-up of drug cocrystals and salts using continuous manufacturing technologies provides high-value pharmaceuticals with economic and environmental benefits.

Combination of co-crystal and nanocrystal techniques to improve the solubility and dissolution rate of poorly soluble drugs

Purpose

Solubility and dissolution rate are essential for the oral absorption and bioavailability of poorly soluble drugs. The aim of this study was to prepare nano-co-crystals by combination of nanocrystal and co-crystal technologies, and investigate its effect, in situ, on increased kinetic solubility and dissolution rate.

Methods

Co-crystals of itraconazole-fumaric acid, itraconazole-succinic acid, indomethacin-saccharin and indomethacin-nicotinamide were prepared and nano-sized by wet milling. The particle size and solid state of the co-crystals were characterized by optical microscope, LD, PCS, DSC and XRPD before and after milling.

Results

300-450 nm sized nano-co-crystals with a stable physical solid state were successfully prepared. Nano-co-crystals exhibited a lower crystallinity reduction than nanocrystals after wet milling. The particle size effect on the kinetic solubility of co-crystals was analysed for macro-, micro- and nano-co-crystals with in situ kinetic solubility studies. The maximum kinetic solubility of nano-co-crystals increased with excess conditions until a plateau. The highest increase was obtained with itraconazole-succinic acid nano-co-crystals with a kinetic solubility of 263.5 ± 3.9 μg/mL which was 51.5 and 6.6 times higher than the solubility of raw itraconazole and itraconazole-succinic acid co-crystal.

Conclusions

The synergistic effect of nanocrystals and co-crystals with regard to increased kinetic solubility and dissolution rate was proven. The combination of the advantages of nanocrystals and co-crystals is a promising formulation strategy to increase both the solubility and dissolution rate of poorly soluble drugs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-022-03243-9.

Kinetic solubility improvement and influence of polymers on controlled supersaturation of itraconazole-succinic acid nano-co-crystals

Nano-co-crystals enhance the solubility and dissolution rate of poorly soluble drugs. The objective of this study was to obtain a better understanding of the dissolution process of nano-co-crystals and of the precipitation inhibition by various polymers. Itraconazole-succinic acid (ITZ-SUC) nano-co-crystal was chosen as model drug formulation to investigate the supersaturation and precipitation inhibition capabilities of various polymers (HPMC E5, HPMC E50, HPMCAS, HPC-SSL, PVPK30 and PVPVA64). The kinetic concentration-time profiles of nano-co-crystal were measured under non-sink conditions with in situ UV-VIS spectroscopy. HPMC E5 performed best by achieving the greatest extended supersaturation/precipitation inhibition. The precipitation inhibition capacity of HPMC E5 was proportional to its concentration. The maximum achievable supersaturation was proportional to the dissolution rate which can be modulated by the rate of supersaturation generation (i.e., addition rate or dose). Supersaturation could be prolonged significantly resulting in 2-5-fold increased area under the dissolution curves compared to nano-co-crystals alone. This effect was limited by a critical excess of undissolved particles with high specific surface area which acted as crystallization seeds resulting in faster precipitation. The study highlighted that a faster dissolution rate and the use of precipitation inhibitors were two key factors determining the extent and time of supersaturation of nano-co-crystals.

Pharmaceutical nanococrystal synthesis: a novel grinding approach

Nanococrystals – a new green in situ surfactant-assisted mechanochemical synthesis.

Nanoconfinement of a Pharmaceutical Cocrystal with Praziquantel in Mesoporous Silica: The Influence of the Solid Form on Dissolution Enhancement

Nanoconfinement is a recent strategy to enhance solubility and dissolution of active pharmaceutical ingredients (APIs) with poor biopharmaceutical properties. In this work, we combine the advantage of cocrystals of racemic praziquantel (PZQ) containing a water-soluble coformer (i.e., increased solubility and supersaturation) and its confinement in a mesoporous silica material (i.e., increased dissolution rate). Among various potential cocrystalline phases of PZQ with dicarboxylic acid coformers, the cocrystal with glutaric acid (PZQ-GLU) was selected and successfully loaded by the melting method into nanopores of SBA-15 (experimental pore size of 5.6 nm) as suggested by physical and spectroscopic characterization using various complementary techniques like N₂ adsorption, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), solid-state NMR (ss-NMR), differential scanning calorimetry (DSC), and field emission-scanning electron microscopy (FE-SEM) analysis. The PZQ-GLU phase confined in SBA-15 presents more mobility according to ss-NMR studies but still retains its cocrystal-like features in the IR spectra, and it also shows depression of the melting transition temperature in DSC. On the contrary, pristine PZQ loaded into SBA-15 was found only in the amorphous state, according to the aforementioned studies. This dissimilar behavior of the composites was attributed to the larger crystal lattice of PZQ over the PZQ-GLU cocrystal (3320.1 vs 1167.9 ų) and to stronger intermolecular interactions between PZQ and GLU, facilitating the confinement of a more mobile solid-like phase in the constrained channels. Powder dissolution studies under extremely nonsink conditions (SI = 0.014) of the confined PZQ-GLU and amorphous PZQ phases embedded in mesoporous silica showed transient supersaturation behavior when dissolving in simulated gastric fluid (HCl pH 1.2 at 37 ± 0.5 °C) in a similar fashion to the bare cocrystal PZQ-GLU. A comparison of the area under the curve (AUC_0-90 min) of the dissolution profiles afforded a dissolution advantage of 2-fold (p < 0.05) of the new solid phases over pristine racemic PZQ after 90 min; under these conditions, the solubilized API reprecipitated as the recently discovered PZQ hemihydrate (PZQ-HH). In the presence of a cellulosic polymer, sustained solubilization of PZQ from composites SBA-15/PZQ or SBA-15/PZQ-GLU was observed, increasing AUC_0-90 min up to 5.1-fold in comparison to pristine PZQ. The combination of a confined solid phase in mesoporous silica and a methylcellulose polymer in the dissolution medium effectively maintained the drug solubilized during times significant to promote absorption. Finally, powder dissolution studies under intermediate nonsink conditions (SI = 1.99) showed a fast release profile from the nanoconfined PZQ-GLU phase in SBA-15, which reached rapid saturation (95% drug dissolved at 30 min); the amorphous PZQ composite and bare PZQ-GLU also displayed an immediate release of the API but at a lower rate (69% drug dissolved at 30 min). In all of these cases, a large dissolution advantage was observed from any of the novel solid phases over PZQ.

Design of ultra-fine carvedilol nanococrystals: Development of a safe and stable injectable formulation

Carvedilol (CAR) is a strategic beta-blocker agent which its application has been limited by its very low water solubility. The present study describes a soluble form of drug based on nano-cocrystal (NCC) anti-solvent precipitation technique. The COSMOquick software was employed to select the optimum coformer (tartaric acid, TA) and organic solvent (acetone) relying on the enthalpy changes of cocrystallization and solubilization. Central Composite Design (CCD) considering the impact of CAR, TA, poloxamer 188 (stabilizer) concentrations, and anti-solvent/solvent ratio on CAR NCCs particle size (PS) could produce ultra-fine NCCs (about 1 nm). The lyophilization of NCCs investigating slow/fast freezing rates, various types and concentrations of cryprotectants and lyoprotectants indicated that PEG and trehalose (5 % w/vconcentration) under slow freezing rate could re-produce the initial PSs successfully. CAR NCCs indicated about 2000 fold increase in solubility compared with pure CAR. DSC and PXRD experiments proved that the formulations containing trehalose led to more crystalline and the ones comprising PEG led to more amorphous structures. Interestingly, the slow freezed PEG protected NCCs were physically stable for at least 18 months. In conclusion, the NCC technology could produce the first safe soluble form of CAR for treating hypertension urgencies easy for industrial scale-up.

An industrial perspective on co-crystals: Screening, identification and development of the less utilised solid form in drug discovery and development

Active pharmaceutical ingredients are commonly marketed as a solid form due to ease of transport, storage and administration. In the design of a drug formulation, the selection of the solid form is incredibly important and is traditionally based on what polymorphs, hydrates or salts are available for that compound. Co-crystals, another potential solid form available, are currently not as readily considered as a viable solid form for the development process. Even though co-crystals are gaining an ever-increasing level of interest within the pharmaceutical community, their acceptance and application is still not as standard as other solid forms such as the ubiquitous pharmaceutical salt and stabilised amorphous formulations. Presented in this chapter is information that would allow for a co-crystal screen to be planned and conducted as well as scaled up using solution and mechanochemistry based methods commonly employed in both the literature and industry. Also presented are methods for identifying the formation of a co-crystal using a variety of analytical techniques as well as the importance of confirming the formation of co-crystals from a legal perspective and demonstrating the legal precedent by looking at co-crystalline products already on the market. The benefits of co-crystals have been well established, and presented in this chapter are a selection of examples which best exemplify their potential. The goal of this chapter is to increase the understanding of co-crystals and how they may be successfully exploited in early stage development.

A Review of Pharmaceutical Nano-Cocrystals: A Novel Strategy to Improve the Chemical and Physical Properties for Poorly Soluble Drugs

Nowadays, many commercial drugs have poor solubility and bioavailability. Cocrystals are formulated to modulate active pharmaceutical ingredients’ properties with improved solubility, dissolution, and bioavailability compared to their pristine individual components in the pharmaceutical industry. Nano-cocrystals, crystals in the nano range, can further enhance these properties because of not only the cocrystal structure, but also the large surface to volume ratio of nanocrystals. Even though there are many studies on cocrystals, the research of pharmaceutical nano-cocrystals is still in the initial stage. Thus, it is necessary to conduct a systematic study on pharmaceutical nano-cocrystals. In this review, the possible preparation approaches of nano-cocrystals have been reported. To have a comprehensive understanding of nano-cocrystals, some analytical techniques and characterizations will be discussed in detail. In addition, the feasible therapeutic application of nano-cocrystals will be presented. This work is expected to provide guidance to develop new nano-cocrystals with commercial value in the pharmaceutical industry.

Application of Fundamental Techniques for Physicochemical Characterizations to Understand Post-Formulation Performance of Pharmaceutical Nanocrystalline Materials

Nanocrystalline materials (NCM, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from drug delivery and electronics to optics. Drug nanocrystals (NC) and nano co-crystals (NCC) are examples of NCM with fascinating physicochemical properties and have attracted significant attention in drug delivery. NCM are categorized by advantageous properties, such as high drug-loading efficiency, good long-term physical stability, steady and predictable drug release, and long systemic circulation time. These properties make them excellent formulations for the efficient delivery of a variety of active pharmaceutical ingredients (API). In this review, we summarize the recent advances in drug NCM-based therapy options. Currently, there are three main methods to synthesize drug NCM, including top-down, bottom-up, and combination methods. The fundamental characterization methods of drug NCM are elaborated. Furthermore, the applications of these characterizations and their implications on the post-formulation performance of NCM are introduced.

Synthesis and Characterization of Nano-Sized 4-Aminosalicylic Acid-Sulfamethazine Cocrystals

Drug–drug cocrystals are formulated to produce combined medication, not just to modulate active pharmaceutical ingredient (API) properties. Nano-crystals adjust the pharmacokinetic properties and enhance the dissolution of APIs. Nano-cocrystals seem to enhance API properties by combining the benefits of both technologies. Despite the promising opportunities of nano-sized cocrystals, the research at the interface of nano-technology and cocrystals has, however, been described to be in its infancy. In this study, high-pressure homogenization (HPH) and high-power ultrasound were used to prepare nano-sized cocrystals of 4-aminosalysilic acid and sulfamethazine in order to establish differences between the two methods in terms of cocrystal size, morphology, polymorphic form, and dissolution rate enhancement. It was found that both methods resulted in the formation of form I cocrystals with a high degree of crystallinity. HPH yielded nano-sized cocrystals, while those prepared by high-power ultrasound were in the micro-size range. Furthermore, HPH produced smaller-size cocrystals with a narrow size distribution when a higher pressure was used. Cocrystals appeared to be needle-like when prepared by HPH compared to those prepared by high-power ultrasound, which had a different morphology. The highest dissolution enhancement was observed in cocrystals prepared by HPH; however, both micro- and nano-sized cocrystals enhanced the dissolution of sulfamethazine.

Cocrystal engineering of pharmaceutical solids: therapeutic potential and challenges

This highlight presents an overview of pharmaceutical cocrystal production and its potential in reviving problematic properties of drugs in different dosage forms. The challenges and future outlook of its translational development are discussed.

Diclofenac-proline nano-co-crystal development, characterization, in vitro dissolution and diffusion study

Nanotechnology has been widely developed to improve the solubility of active pharmaceutical ingredients. Co-crystal discovery has also taken much attention in drug design and development. A combination of the two techniques generates “nano-co-crystallization”, a new approach to obtaining the superior character of drugs. Previously, a new diclofenac-proline co-crystal (DPC) arrangement has been reported. The present research attempted to develop a nano-diclofenac-proline-co-crystal (NDPC) and to evaluate its formation kinetics, and dissolution-diffusion improvements. Both top-down and bottom-up methods optimized nano-co-crystal production. The top-down technique was used through the wet milling procedure and neat grinding procedures, while the bottom-up technique was performed through the globule inversion phase and fast evaporation assisted microwaving. The NDPCs obtained were then characterized by dynamic light scattering, binocular microscope, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, powder x-ray diffractometry, and Fourier transform infrared spectrophotometry. The kinetics of NDPC formation was determined based on the difference of microwaving versus the co-crystal yield, which was analyzed using Fourier transform infrared spectroscopy. Dissolution was tested by type 2 apparatus, and diffusion was tested using Franz diffusion cells. The bottom-up method by fast evaporation assisted microwaving provided the best nano-co-crystal with a mean diameter of 598.2 ± 63.2 nm and a polydispersity index of 0.278 ± 0.062. Nano-co-crystal formation kinetic, which was evaluated by FTIR, indicated to follow first order. Finally, NDPC showed the superior dissolution and diffusion profile than conventional-DPC. In this study, we demonstrate a promising alternative for improving the dissolution and diffusion of the drug by nano-co-crystallization.

Preparation and optimization of nano-sized cocrystals using a quality by design approach

Nano-cocrystals were optimized using the L-18 Hunter design. Selection of solvent and antisolvent was made using the Damkohler number.

Bioavailability Enhancement of Poorly Soluble Drugs: The Holy Grail in Pharma Industry

Background:

Bioavailability, one of the prime pharmacokinetic properties of a drug, is defined as the fraction of an administered dose of unchanged drug that reaches the systemic circulation and is used to describe the systemic availability of a drug. Bioavailability assessment is imperative in order to demonstrate whether the drug attains the desirable systemic exposure for effective therapy. In recent years, bioavailability has become the subject of importance in drug discovery and development studies.

Methods:

A systematic literature review in the field of bioavailability and the approaches towards its enhancement have been comprehensively done, purely focusing upon recent papers. The data mining was performed using databases like PubMed, Science Direct and general Google searches and the collected data was exhaustively studied and summarized in a generalized manner.

Results:

The main prospect of this review was to generate a comprehensive one-stop summary of the numerous available approaches and their pharmaceutical applications in improving the stability concerns, physicochemical and mechanical properties of the poorly water-soluble drugs which directly or indirectly augment their bioavailability.

Conclusion:

The use of novel methods, including but not limited to, nano-based formulations, bio-enhancers, solid dispersions, lipid-and polymer-based formulations which provide a wide range of applications not only increases the solubility and permeability of the poorly bioavailable drugs but also improves their stability, and targeting efficacy. Although, these methods have drastically changed the pharmaceutical industry demand for the newer potential methods with better outcomes in the field of pharmaceutical science to formulate various dosage forms with adequate systemic availability and improved patient compliance, further research is required.

Recent advances in improving oral drug bioavailability by cocrystals

Introduction: Oral drug delivery is the most favored route of drug administration. However, poor oral bioavailability is one of the leading reasons for insufficient clinical efficacy. Improving oral absorption of drugs with low water solubility and/or low intestinal membrane permeability is an active field of research. Cocrystallization of drugs with appropriate coformers is a promising approach for enhancing oral bioavailability.

Methods: In the present review, we have focused on recent advances that have been made in improving oral absorption through cocrystallization. The covered areas include supersaturation and its importance on oral absorption of cocrystals, permeability of cocrystals through membranes, drug-coformer pharmacokinetic (PK) interactions, conducting in vivo-in vitro correlations for cocrystals. Additionally, a discussion has been made on the integration of nanocrystal technology with supramolecular design. Marketed cocrystal products and PK studies in human subjects are also reported.

Results: Considering supersaturation and consequent precipitation properties is necessary when evaluating dissolution and bioavailability of cocrystals. Appropriate excipients should be included to control precipitation kinetics and to capture solubility advantage of cocrystals. Beside to solubility, cocrystals may modify membrane permeability of drugs. Therefore, cocrystals can find applications in improving oral bioavailability of poorly permeable drugs. It has been shown that cocrystals may interrupt cellular integrity of cellular monolayers which can raise toxicity concerns. Some of coformers may interact with intestinal absorption of drugs through changing intestinal blood flow, metabolism and inhibiting efflux pumps. Therefore, caution should be taken into account when conducting bioavailability studies. Nanosized cocrystals have shown a high potential towards improving absorption of poorly soluble drugs.

Conclusions: Cocrystals have found their way from the proof-of-principle stage to the clinic. Up to now, at least two cocrystal products have gained approval from regulatory bodies. However, there are remaining challenges on safety, predicting in vivo behavior and revealing real potential of cocrystals in the human.

A nano-cocrystal strategy to improve the dissolution rate and oral bioavailability of baicalein

Baicalein (BE) is one of the main active flavonoids representing the variety of pharmacological effects including anticancer, anti-inflammatory and cardiovascular protective activities, but it's very low solubility, dissolution rate and poor oral absorption limit the therapeutic applications. In this work, a nano-cocrystal strategy was successfully applied to improve the dissolution rate and bioavailability of BE. Baicalein-nicotinamide (BE-NCT) nano-cocrystals were prepared by high pressure homogenization and evaluated both in vitro and in vivo. Physical characterization results including scanning electron microscopy, dynamic light scattering, powder X-ray diffraction and differential scanning calorimetry demonstrated that BE-NCT nano-cocrystals were changed into amorphous state with mean particle size of 251.53 nm. In the dissolution test, the BE-NCT nano-cocrystals performed 2.17-fold and 2.54-fold enhancement than BE coarse powder in FaSSIF-V2 and FaSSGF. Upon oral administration, the integrated AUC_0 − t of BE-NCT nano-cocrystals (6.02-fold) was significantly higher than BE coarse powder (1-fold), BE-NCT cocrystals (2.87-fold) and BE nanocrystals (3.32-fold). Compared with BE coarse powder, BE-NCT cocrystals and BE nanocrystals, BE-NCT nano-cocrystals possessed excellent performance both in vitro and in vivo evaluations. Thus, it can be seen that nano-cocrystal is an appropriate novel strategy for improving dissolution rate and bioavailability of poor soluble natural products such as BE.