Soluble Active Pharmaceutical Ingredients Research Articles

Determination of Thermodynamic Solubility of Active Pharmaceutical Ingredients for Veterinary Species: A New USP General Chapter

Determination of Thermodynamic Solubility of Active Pharmaceutical Ingredients for Veterinary Species: A New USP General Chapter

Review on: New approaches in self micro-emulsifying drug delivery system

Self Micro-Emulsifying drug delivery system is recent and novel approaches have been attracted to considerable interest as an efficient means for improving solubility, dissolution rate and oral bioavailability of API (Active Pharmaceutical Ingredient). Now a day's up to 40% of new drug chemical entities developed and discovered by pharmaceutical industry by recent years such as poorly soluble and highly permeable lipid based drug delivery system (such as lipophilic compound). SMEDDS are most important approaches for improvement of solubility enhancement of lipid based BCS Class II drug delivery system. SMEDDS is isotropic mixture of oil, hydrophilic surfactant and co-surfactant and solubilised drug. This formulation spontaneously from fine oil-in-water microemulsion upon dilution with water. They can be encapsulated in hard or soft gelatin capsule or to form other solid dosage forms by using various recently developed techniques such as spry drying, adsorption to solid carrier, melt granulation, melt extrusion/extrusion speronization and encapsulation in liquid and semisolid dosage forms. Oral delivery of such drugs is complicated for the reason that of their low bioavailability, high intra and inter-subject variability and not have dose linearity. The article gives complete overview of SMEDDS but special attention has been shown to formulation, design, evaluation and application of SMEDDS.

An investigation into the factors governing the degree of dissolution enhancement of solid dispersion for poorly soluble drugs

AbstractSolid dispersion (SD) formulation has attracted much attention due to its potential in enhancing dissolution performances of poorly soluble active pharmaceutical ingredients (API). Recently, a review on dissolution performances of SDs classifies the improvement into 3 categories, where 82 % of the studies showed improved bioavailability, 8 % showed reduced bioavailability and 10 % revealed similar bioavailability as compared to pure APIs. This indicates the inconsistent degrees of dissolution improvement of poorly soluble APIs in SD. Although a few factors related to the choice of carriers have been suggested to contribute to the dissolution improvement, however, the underlying factor determining the discrepancy in the degree of dissolution improvement remains in vague. It is hypothesized that the API contributes to the degree of dissolution improvement of SD. Hence, the factor of amorphous solubility advantage of API which leads to the different degrees of dissolution enhancement of SD is investigated in this research. Polyvinylpyrrolidone vinyl acetate (PVPVA)-based SD is prepared with three poorly soluble APIs. Physicochemical properties of SD were characterized using infrared spectroscopy, differential scanning calorimetry (DSC) and X-ray powder diffraction. The dissolution efficiency of each SD was calculated and compared to physical mixture and pure API. Theoretical amorphous solubility advantage for each API was calculated using the thermal properties obtained from DSC. The calculated values were found to be correlating well with the dissolution enhancement of the respective SDs. Hence, this theoretical approach can be utilized as an initial screening tool of API candidates in SD formulation during early pharmaceutical development.

Long-Term Physical Stability of PVP- and PVPVA-Amorphous Solid Dispersions.

The preparation of amorphous solid dispersion (ASD) formulations is a promising strategy to improve the bioavailability of an active pharmaceutical ingredient (API). By dissolving the API in a polymer it is stabilized in its amorphous form, which usually shows higher water solubility than its crystalline counterpart. To prevent recrystallization, the long-term physical stability of ASD formulations is of big interest. In this work, the solubility of the APIs acetaminophen and naproxen in the excipient polymers poly(vinylpyrrolidone) (PVP K25) and poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA64) was calculated with three models: the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), the Flory-Huggins model (FH), and an empirical model (Kyeremateng et al., J. Pharm. Sci, 2014, 103, 2847-2858). PC-SAFT and FH were further used to predict the influence of relative humidity (RH) on the API solubility in the polymers. The Gordon-Taylor equation was applied to model the glass-transition temperature of dry ASD and at humid conditions. The calculations were validated by 18 months-long stability studies at standardized storage conditions, 25 °C/0% RH, 25 °C/60% RH, and 40 °C/75% RH. The results of the three modeling approaches for the API solubility in polymers agreed with the experimental solubility data, which are only accessible at high temperatures in dry polymers. However, at room temperature FH resulted in a lower solubility of the APIs in the dry polymers than PC-SAFT and the empirical model. The impact of RH on the solubility of acetaminophen was predicted to be small, but naproxen solubility in the polymers was predicted to decrease with increasing RH with both, PC-SAFT and FH. At 25 °C/60% RH and 40 °C/75% RH, PC-SAFT is in agreement with all results of the long-term stability studies, while FH underestimates the acetaminophen solubility in PVP K25 and PVPVA64.

Regenerated cellulose capsules for controlled drug delivery: Part IV. In-vitro evaluation of novel self-pore forming regenerated cellulose capsules

In the present work, the release mechanisms of active pharmaceutical ingredients (APIs) enclosed in self-pore forming regenerated cellulose (RC) two-piece hard shell capsules are described. The RC capsules were fabricated using a modified dip-coating approach, which yielded an assembled dosage form that was equivalent in size and shape to a conventional gelatin two-piece hard shell capsule. Drug release characteristics from RC capsules were evaluated using potassium chloride, diphenhydramine hydrochloride, tramadol hydrochloride, niacinamide, acetaminophen and ketoprofen as model APIs. The RC capsules act as a barrier coated reservoir device that releases the enclosed API at a zero order release rate. When comparing all the API's release behavior from RC capsules, a power-law relationship was observed between their zero-order release rates and their respective aqueous solubilities. Osmotic as well as diffusive mechanisms are involved in the release of the enclosed API. The osmotic mechanism's contribution to zero order release rate increases as the aqueous solubility of the tested APIs inside the capsule increases. The osmotic mediated flux and the apparent diffusivity of the APIs through the capsule wall is a competitive process and the osmotic mediated flux of the enclosed API begins to override its diffusivity through the capsule wall as the API solubility increases. This behavior is attributed to the wide range of pore sizes observed in RC membranes, from our prior analysis. The fluid permeability analysis shows that the RC capsules presented in this work may be better suited for osmotic drug delivery applications than conventional encapsulated systems described in the literature.

Analysis of spironolactone polymorphs in active pharmaceutical ingredients and their effect on tablet dissolution profiles

Spironolactone (SPR) is a steroidal drug administered as a potassium-sparing diuretic for high blood pressure treatment. The drug shows incomplete gastrointestinal absorption due to its poor aqueous solubility. The physicochemical properties of SPR in crystal forms I and II suggest that differences in their aqueous solubility may lead to a lack of bioequivalence between solid-state formulations. In this study, SPR polymorphs in five batches of active pharmaceutical ingredients (APIs) from three manufacturers were characterized using powder X-ray diffraction, infrared spectroscopy, thermal analysis, and solubility measurements. SPR tablets (50 mg) were manufactured in our laboratory using API in pure form II, and API in form II contaminated with form I, which was found in a commercial batch. Physicochemical quality evaluations of the manufactured tablets, along with five SPR tablets marketed in Brazil, were performed, and results indicated differences in their dissolution profiles. In the manufactured tablets, differences were associated with the increased solubility of API in form II contaminated with form I compared to API in pure form II. In the marketed SPR tablets, the formulation composition demonstrated an important role in the dissolution rate of the drug, leading to lack of pharmaceutical equivalence among the drug products.

ChemInform Abstract: Characterization and Quality Control of Pharmaceutical Cocrystals

AbstractReview: 106 refs.

Development of a novel physico-chemically and microbiologically stable oral solution of flecainide for pediatrics

There is as yet no commercialized preparation for oral administration of flecainide acetate (FA) to children. In such cases, manipulation of commercial tablets is the usual practice in pharmacy services of hospitals and compounding pharmacies, to provide a suitable dosage form for this vulnerable pediatric population group. In this study, we have formulated FA as an oral solution, as an alternative to the suspension elaborated from commercial tablets. Due to this sensitivity of young patients, we have used the pure active pharmaceutical ingredient (API) and the lowest permitted levels of pediatric excipients. Despite being a highly soluble API, only one of the formulations appears as a transparent solution due to complete FA solubilization. The proposed formulation is physico-chemically and microbiologically stable and the mass and dose uniformity is appropriate for 30 days’ storage at 25 °C.

Double Salt Ionic Liquids Containing the Trihexyl(tetradecyl)phosphonium Cation: The Ability to Tune the Solubility of Aromatics, Ethers, and Lipophilic Compounds

Ionic liquids (ILs) certainly have some interesting properties and this has led to tremendous growth in interest, knowledge, and applications of these materials in a diverse array of science and technology. However, the field is still dominated by study of the simplest binary salts and an over reliance on ‘magic’ solvent properties which currently limits their creative use for new technologies. Lately, the scientific community has been attracted towards “IL/IL mixtures” prepared by mixing two or more ILs, and (as was the case with the early studies of the binary salts), a focus on specific physicochemical properties. Interestingly, crystalline salts dissolved in ILs are seen as a different class of liquids (e.g., high ionicity ILs). We have found that the physical, chemical, and biological (i.e., the materials) properties of IL/IL mixtures (or Double Salt Ionic Liquids, DSILs, as we like to call them) seem to be mainly controlled by the intrinsic ion interactions which are influenced by the exact ion composition. Perhaps, a new way of thinking about these multi-ion fluids is needed in order to direct research toward an understanding of the complex and varied types of interionic forces possible in a liquid. We have proposed the DSIL concept to help guide our work towards obtaining this deeper understanding. In this nomenclature, any homogeneous liquid containing three or more ions (no matter how they are prepared) are described as DSILs and are defined by the specific ion combinations present. In this presentation, these concepts will be illustrated by discussion of the chemical, physical, and biological properties of several DSIL systems chosen to explore different interactions between the ions (i.e., Coulombic, hydrogen bonding, dispersion, etc.). While we will present physical properties as a function of composition, we will focus more on chemical properties illustrated by the solubilities of pharmaceuticals and on biological properties illustrated by changes in membrane transport, both as a function of ion composition. Spectroscopic studies will be presented to provide insight into specific ion-ion interactions. For example, the solubility of active pharmaceutical ingredients with different acidity and lipophilicity are finely tunable by varying the ratio of the ions (Figure 1). Such studies support the concept that each DSIL is a unique ionic fluid that is able to provide tunable property sets derived from the ions present and that these properties can be controlled by choosing the nature and the abundance of the ions. Figure 1

Continuous reactive crystallization of pharmaceuticals using impinging jet mixers

For reactive crystallization of pharmaceuticals that show a rapid reaction rate, low solubility of active pharmaceutical ingredient and hence a large supersaturation, it was found in a recent study that a process design which integrates an impinging jet mixer and batch stirred tank produces high quality crystals. The current investigation examines if the short processing time of reactive crystallization permits the impinging jet mixer—stirred tank design to be modified to operate in a continuous mode. The new design combines an impinging jet mixer for feed introduction and reaction with a continuous stirred tank reactor (CSTR) and tubular reactor for crystal growth. A study of reactive crystallization of sodium cefuroxime (an antibiotic), using first a 1L CSTR then scaling to a 50L CSTR, found that the new design produces crystals of higher crystallinity, narrower particle size, and improved product stability, than batch crystallizers. © 2016 American Institute of Chemical Engineers AIChE J, 63: 967–974, 2017

Micro-scale prediction method for API-solubility in polymeric matrices and process model for forming amorphous solid dispersion by hot-melt extrusion

A new predictive micro-scale solubility and process model for amorphous solid dispersions (ASDs) by hot-melt extrusion (HME) is presented. It is based on DSC measurements consisting of an annealing step and a subsequent analysis of the glass transition temperature (Tg). The application of a complex mathematical model (BCKV-equation) to describe the dependency of Tg on the active pharmaceutical ingredient (API)/polymer ratio, enables the prediction of API solubility at ambient conditions (25°C). Furthermore, estimation of the minimal processing temperature for forming ASDs during HME trials could be defined and was additionally confirmed by X-ray powder diffraction data. The suitability of the DSC method was confirmed with melt rheological trials (small amplitude oscillatory system). As an example, ball milled physical mixtures of dipyridamole, indomethacin, itraconazole and nifedipine in poly(vinylpyrrolidone-co-vinylacetate) (copovidone) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus®) were used.

Influence of Coformer Stoichiometric Ratio on Pharmaceutical Cocrystal Dissolution: Three Cocrystals of Carbamazepine/4-Aminobenzoic Acid.

Cocrystallization is a technique to optimize solid forms that shows great potential to improve the solubility of active pharmaceutical ingredients (APIs). In some systems, an API can form cocrystals in multiple stoichiometries with the same coformer. However, it remains unclear how coformer stoichiometry influences solubility. This paper investigates the pharmaceutical:coformer pair carbamazepine (CBZ)/p-aminobenzoic acid (PABA); both CBZ/PABA 1:1 and 2:1 cocrystals are known, and a novel 4:1 CBZ/PABA cocrystal is reported here. The 4:1 cocrystal is structurally characterized, and phase stability data suggest that it is a thermodynamically unstable form. Dissolution experiments show that there is no correlation between the cocrystal stoichiometry and dissolution rate in this system. On the other hand, with the relatively weak intermolecular interactions, metastable forms can be beneficial to dissolution rate, which suggests that more effort should be devoted to cocrystal production with kinetic growth methods.

Ibuprofen-Amino Acids Co-Crystal Screening Via Co-Grinding Methods

The importance of pharmaceutical co-crystals now has been recognized in order to improve the research and development in pharmaceutical industries. Low solubility of active pharmaceutical ingredient (API) has led to the growth of new pharmaceutical co-crystals formation as it enhances the physicochemical properties of the API. In this works, preparation of new co-crystal formation between ibuprofen (IBP) with selected amino acid compounds were performed by using dry grinding and liquid assisted grinding (LAG) techniques. Ibuprofen (IBP) was selected as the API meanwhile glycine (GLY), L-alanine (ALA) and L-proline (PRO) were selected as co-crystal former (CCF) agents. The products of IBP-co-former from grinding experiments for the formation of co-crystals were characterized and verified using X-Ray Powder Diffraction (XRPD), Differential Scanning Calorimetry (DSC) and Fourier Transform Infra-Red Spectroscopy (FTIR). The finding reveals that the IBP-PRO co-crystals have successfully formed. For IBP-PRO system, new crystalline peaks from XRPD were recorded at 2θ values of 4.374°, 5.436° and 10.944° from dry grinding technique and 4.41°, 5.436° and 10.962° for liquid assisted grinding (LAG) technique. A new melting point of 257.49 °C was discovered for IBP-ALA indicates the possibility of co-crystals formation. On the other hand, the analysis for IBP-GLY shows that no co-crystals formed in the system.

Characterization and Quality Control of Pharmaceutical Cocrystals.

Recent active research and new regulatory guidance on pharmaceutical cocrystals have increased the rate of their development as promising approaches to improve handling, storage stability, and bioavailability of poorly soluble active pharmaceutical ingredients (APIs). However, their complex structure and the limited amount of available information related to their performance may require development strategies that differ from those of single-component crystals to ensure their clinical safety and efficacy. This article highlights current methods of characterizing pharmaceutical cocrystals and approaches to controlling their quality. Different cocrystal regulatory approaches between regions are also discussed. The physical characterization of cocrystals should include elucidating the structure of their objective crystal form as well as their possible variations (e.g., polymorphs, hydrates). Some solids may also contain crystals of individual components. Multiple processes to prepare pharmaceutical cocrystals (e.g., crystallization from solutions, grinding) vary in their applicable ingredients, scalability, and characteristics of resulting solids. The choice of the manufacturing method affects the quality control of particular cocrystals and their formulations. In vitro evaluation of the properties that govern clinical performance is attracting increasing attention in the development of pharmaceutical cocrystals. Understanding and mitigating possible factors perturbing the dissolution and/or dissolved states, including solution-mediated phase transformation (SMPT) and precipitation from supersaturated solutions, are important to ensure the bioavailability of orally administrated lower-solubility APIs. The effect of polymer excipients on the performance of APIs emphasizes the relevance of formulation design for appropriate use.

Solubility Measurement and Simulation of Rivaroxaban (Form I) in Solvent Mixtures from 273.15 to 323.15 K

The solubility of active pharmaceutical ingredients in various solvents is crucial to their industrial production and the development to final formulations. In this work, the solubility of rivaroxaban (form I) in the binary solvent mixtures of 1-methyl-2-pyrrolidinone with water, methanol, ethanol, and isopropanol from 273.15 to 323.15 K has been experimentally measured. Meanwhile, the dependence of the measured solubility on the temperature as well as on the composition of solvent mixtures has been simulated by Jouyban-Acree (JA) and nonrandom two liquid (NRTL) equations, respectively. The results show that as to the solubility simulation of the studied system JA and NRTL give average relative deviations of 0.1081 and 0.1064, respectively, suggesting that both JA and NRTL can act as an efficient simulation tool for the solubility of rivaroxaban (form I) in pure and mixture solvents at various temperatures.

Understanding Critical Quality Attributes for Nanocrystals from Preparation to Delivery.

Poor solubility of active pharmaceutical ingredients (APIs) is a great challenge for the pharmaceutical industry and, hence, drug nanocrystals are widely studied as one solution to overcome these solubility problems. Drug nanocrystals have comparatively simple structures which make them attractive for the formulation for poorly soluble drugs, and their capability to improve the dissolution in vitro is easily demonstrated, but turning the in vitro superior properties of nanocrystals to success in vivo, is often demanding: controlled (including enhanced) drug dissolution followed by successful permeation is not guaranteed, if for example, the dissolved drug precipitates before it is absorbed. In this review critical quality attributes related to nanocrystal formulations from production to final product performance in vivo are considered. Many important parameters exist, but here physical stability (aggregation tendency and solid state form), solubility properties influencing dissolution and supersaturation, excipient use to promote the maintenance of supersaturation, and finally the fate of nanocrystals in vivo are the main subjects of our focus.

Use of Polyvinyl Alcohol as a Solubility-Enhancing Polymer for Poorly Water Soluble Drug Delivery (Part 1).

Polyvinyl alcohol (PVAL) has not been investigated in a binary formulation as a concentration-enhancing polymer owing to its high melting point/high viscosity and poor organic solubility. Due to the unique attributes of the KinetiSol® dispersing (KSD) technology, PVAL has been enabled for this application and it is the aim of this paper to investigate various grades for improvement of the solubility and bioavailability of poorly water soluble active pharmaceutical ingredients. Solid amorphous dispersions were created with the model drug, itraconazole (ITZ), at a selected drug loading of 20%. Polymer grades were chosen with variation in molecular weight and degree of hydroxylation to determine the effects on performance. Differential scanning calorimetry, powder X-ray diffraction, polarized light microscopy, size exclusion chromatography, and dissolution testing were used to characterize the amorphous dispersions. An in vivo pharmacokinetic study in rats was also conducted to compare the selected formulation to current market formulations of ITZ. The 4-88 grade of PVAL was determined to be effective at enhancing solubility and bioavailability of itraconazole.

High-Throughput Raman Spectroscopy Screening of Excipients for the Stabilization of Amorphous Drugs.

Low aqueous solubility of active pharmaceutical ingredients (APIs) is an enduring problem in pharmaceutical development, and it is becoming increasingly prevalent among new drug candidates. It is estimated that about 40% of drugs in the development pipeline and approximately 60% of the drugs coming directly from discovery suffer from poor aqueous solubility and slow dissolution, thereby reducing their bioavailability and efficacy and thus preventing their commercialization. It is well known that utilizing the amorphous form of a drug can be a useful approach to improve the dissolution rate and solubility of poorly water-soluble APIs. Amorphous compounds are thermodynamically unstable, but they can be stabilized by combining them with a carrier polymer (excipient) to form a solid dispersion. High-throughput Raman spectroscopy was used in this study to identify excipients that promote formation and stabilization of the amorphous drug form in solid dispersions. Four model APIs were used as poorly soluble drug candidates: ketoprofen, danazol, griseofulvin, and probucol. The Raman signals of excipients were generally negligible, and therefore Raman bands from the drugs were used with minimal spectral pre-processing. By comparing Raman spectra collected from the APIs in the crystalline and molten state, appropriate spectral features and regions were identified for the development of semi-quantitative methods to determine the amorphous content for each API. It is demonstrated that methods based on peak intensity ratio, peak width, peak distance, and classical least squares can all be effective methods for the screening of excipients. Interesting excipient-dependent phase transformation behavior was also observed for probucol.

Salt-kneading: alternative sizing of active pharmaceutical ingredients?

The most of currently produced active pharmaceutical ingredients (APIs) are poorly soluble in the human body. One of the options how to increase their dissolution rate is reducing their particle size. If very small particles of API are desired, traditional milling methods often cause smeared, agglomerated or non-flowing particles due to the forces applied. We tried to compare some of milling methods with the salt-kneading method, which is not typically used in the pharmaceutical industry. Salt-kneading process is driven by several variable parameters (e.g. the amount, hardness and particle size of the salt-kneading material), which influence the degree of size reduction of API particles which are chafed by a surplus of salt-kneading material. A model poorly-soluble API was separately processed with oscillation mill, vibratory mill and kneader; and the morphology, size distribution and solid form of prepared particles were analyzed. Our basic variation of salt-kneading parameters showed the potential of the salt-kneading method, which appears a very effective method of API controlled reduction. The final size can be modified according to the amount and properties of the salt-kneading material. The availability of such a method equips pharmaceutical scientists with a size-reduction method that provides very small, rounded and free-flowing particles of the poorly soluble API and reduces non-preferred needle shape.

Determination and prediction of solubilities of active pharmaceutical ingredients in selected organic solvents

The aim of this work was to measure the solubilities of active pharmaceutical ingredients (APIs) in various organic solvents using the synthetic-visual method. Two non-steroidal anti-inflammatory drugs, i.e., acetylsalicylic acid and acetaminophen, and two histamine H2 receptor antagonists, i.e., cimetidine and famotidine, were selected as the APIs. The solubilities of these APIs in different organic solvents, namely methanol, ethanol, 2-propanol, 1-octanol, and poly(ethylene glycol) 400, were determined in the temperature range of 260–360K. Cimetidine and famotidine, which have several polymorphs, were characterized using powder X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry before the solubility measurements. The experimental results for the APIs except famotidine show that the solubilities at a given temperature decreased with increasing carbon number of the alcohol. The solubility data were represented by two activity coefficient models: NRTL and UNIQUAC. In addition, predictions of the solubilities using the group contribution models Pharma Modified UNIFAC and modified UNIFAC (Dortmund) were also performed. The predictions obtained using Pharma Modified UNIFAC were better than those obtained using modified UNIFAC (Dortmund).