Improved oral absorption of a poorly water-soluble drug, HO-221, by wet-bead milling producing particles in submicron region

Matrix effects in nilotinib formulations with pH-responsive polymer produced by carbon dioxide-mediated precipitation

Factors determining the pH-controlled dissolution kinetics of nilotinib formulations with the pH-titrable polymer hydroxypropyl methylcellulose phthalate, obtained by carbon dioxide-mediated precipitation, were mechanistically examined in acid and neutral environment. The matrix effect, modulating the drug dissolution, was characterized with a battery of physicochemical methodologies, including ToF-SIMS for surface composition, SAXS/WAXS and modulated DSC for crystallization characterization, and simultaneous UV-imaging and Raman spectroscopy for monitoring the dissolution process in detail. The hybrid particle formulations investigated consisted of amorphous nilotinib embedded in a polymer matrix in single continuous phase, displaying extended retained amorphicity also under wet conditions. It was demonstrated by Raman and FTIR spectroscopy that the efficient drug dispersion and amorphization in the polymer matrix were mediated by hydrogen bonding between the drug and the phthalate groups on the polymer. Simultaneous Raman and UV-imaging studies of the effect of drug load on the swelling and dissolution of the polymer matrix revealed that high nilotinib load prevented matrix swelling on passage from acid to neutral pH, thereby preventing re-precipitation and re-crystallization of incorporated nilotinib. These findings provide a mechanistic foundation of formulation development of nilotinib and other protein kinase inhibitors, which are now witnessing an intense therapeutic and industrial attention due to the difficulty in formulating these compounds so that efficient oral bioavailability is reached.

Characterization of a riboflavin non-aqueous nanosuspension prepared by bead milling for cutaneous application

The purpose of this study was to characterize the non-aqueous nanosuspension of a hydrophilic drug prepared by bead milling for cutaneous application. Riboflavin was used as the model hydrophilic drug. The non-aqueous nanosuspensions were prepared by grinding riboflavin with zirconia beads using eight non-aqueous bases. The mean particle size of riboflavin in the suspensions ranged from 206 to 469 nm, as determined by the dynamic light scattering method. Among the well-dispersed samples, riboflavin nanosuspension prepared in oleic acid was selected for evaluation of the drug permeability through rat skin. The cumulative amount and permeation rate of riboflavin from the nanosuspension were approximately three times higher than those for unprocessed riboflavin in oleic acid. Fluorescence imaging of the riboflavin nanosuspension suggested improved penetration of riboflavin into the stratum corneum. Furthermore, the addition of polysorbate 65 or polyglyceryl-6 polyricinoleate to the nanosuspension prepared in oleic acid markedly improved the riboflavin dispersibility. These results show that the preparation of a nanosuspension in a non-aqueous base by bead milling is one of the simple methods to improve the skin permeability of hydrophilic drugs.

Heat induced evaporative antisolvent nanoprecipitation (HIEAN) of itraconazole

Itraconazole (ITR) is an antifungal drug with a limited bioavailability due to its poor aqueous solubility. In this study, ITR was used to investigate the impact of nanonisation and solid state change on drug's apparent solubility and dissolution. A bottom up approach to the production of amorphous ITR nanoparticles (NPs), composed of 100% drug, with a particle diameter below 250 nm, using heat induced evaporative antisolvent nanoprecipitation (HIEAN) from acetone was developed. The NPs demonstrated improved solubility and dissolution in simulated gastro-intestinal conditions when compared to amorphous ITR microparticles. The incorporation of polyethylene glycol (PEG) or its methoxylated derivative (MPEG) as a stabiliser enabled the production of smaller NPs with narrower particle size distribution and enhanced apparent solubility. MPEG stabilised NPs gave the greatest ITR supersaturation levels (up to 11.6±0.5 μg/ml) in simulated gastric fluids. The stabilising polymer was in an amorphous state. Dynamic vapour sorption data indicated no solid state changes in NP samples with water vapour at 25 °C, while crystallisation was apparent at 50 °C. HIEAN proved to be an efficient method of production of amorphous ITR NPs, with or without addition of a polymeric stabiliser, with enhanced pharmaceutical properties.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Crystalline nanosuspensions as potential toxicology and clinical oral formulations for BCS II/IV compounds

Nanosuspensions, formulations based on the reduction of the active pharmaceutical ingredient (API) particle size in the sub-micron range and most typically around 100-200 nm, represent a valuable option for formulators to facilitate oral absorption of Biopharmaceutics Classification System class II and IV compounds. Their ability to increase the API dissolution rate and subsequent absorption and thus oral bioavailability has been demonstrated in preclinical and clinical settings. This review summarizes the current experience in the biopharmaceutic field with the use of nanosuspensions as oral delivery formulations. The principles behind nanosuspensions as well as the in vitro and in silico evaluation are discussed, while examples are presented highlighting both successes as well as limitations in their application as either toxicology or clinical formulations.

Preparation and characterization of nimesulide containing nanocrystal formulations

The aim of this study was to develop and characterize nanocrystal formulation containing nimesulide. Physical mixture of drug and excipient (nimesulide:pluronic F127, 1:0.5) was also prepared to compare the efficiency of formulations. The physicochemical characteristics of the formulations were determined by means of Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and X-ray diffractometry. Particle size, saturation solubilities as a function of pH, and permeability across Caco-2 monolayers were determined for nimesulide in powder, physical mixture, and nanocrystal formulations. In FT-IR analysis, the characteristic peaks that belong to nimesulide were seen in all formulations. X-ray diffractograms displayed that crystalline structure of nimesulide was conserved in the nanocrystal formulation. The interaction between nimesulide and pluronic F127 was demonstrated by DSC analysis. In all conditions, the average particle size of the nanocrystal formulations decreased significantly (p < 0.05) as compared with nimesulide and physical mixture. The solubility of nimesulide in nanocrystal formulation was higher than those of nimesulide in powder and physical mixture. Permeability studies revealed that nimesulide is a highly permeable compound whether in powder form or in physical mixture and nanocrystal formulation. All these results clearly demonstrate that aqueous solubility of poorly water-soluble compounds can be improved by preparing nanocrystal formulations.

A smaller particle size improved the oral bioavailability of monkey head mushroom, Hericium erinaceum, powder resulting in enhancement of the immune response and disease resistance of white shrimp, Litopenaeus vannamei

The effects of different particle sizes (100-150, 74-100, and <74 μm) of powder of the dried and ground stipe from the monkey head mushroom, Hericium erinaceum, on the immune response and disease resistance of white shrimp, Litopenaeus vannamei, against the pathogen, Vibrio alginolyticus, were examined. Mushroom powder with a particle size of <74 μm had a significantly higher effect on the disease resistance of shrimp compared to particle sizes of >74 μm. Mortality of shrimp after being injected with V. alginolyticus was particle size-dependent, increasing from 66.7% ± 3.3%-93.3% ± 3.3% with diets containing stipe particle sizes of <74 and 100-150 μm, respectively. The mortality of shrimp fed the diet containing <74-μm stipe powder for 28 days was significant lower than that of shrimp fed with the control diet and the diet containing 74-100-μm stipe powder after being challenged by V. alginolyticus. The optimal concentration of the <74-μm mushroom powder for enhancing the immune response and disease resistance of shrimp was 0.2 μg (g shrimp)(-1) day(-1). No significant change in the total hemocyte count, differential hemocyte count, glutathione reductase, or phagocytic activity was found in shrimp fed the control diet and mushroom powder-containing diet at a level of up to 0.2 μg (g shrimp)(-1) day(-1). Shrimp fed 0.2 μg (g shrimp)(-1) day(-1) of a mushroom-containing diet had a significantly higher disease resistance to V. alginolyticus via an increase in phenoloxidase activity, respiratory bursts, superoxide dismutase activity, and glutathione peroxidase activity. Therefore, a diet containing the stipe powder of monkey head mushroom with a particle size <74 μm at a level of 0.2 μg (g shrimp)(-1) day(-1) was found to enhance the immunity and disease resistance of shrimp.

Novel crystalline solid dispersion of tranilast with high photostability and improved oral bioavailability

Tranilast (TL) is an anti-allergic agent and widely used in the clinical treatment of bronchial asthma, atopic rhinitis, atopic dermatitis and keloids. However, therapeutic potential of TL could be partly limited because of its poor solubility, bioavailability, and photostability. To overcome these drawbacks, crystalline solid dispersion of TL (CSD/TL) was prepared by wet-milling technique with aim of improving physicochemical and pharmacokinetic properties. Physicochemical properties of the formulations prepared were characterized by laser diffraction and dynamic light scattering for particle size analysis, scanning electron microscope for morphological analysis, and powder X-ray diffraction and differential scanning calorimetry for crystallinity assessment. TL particles in CSD/TL appeared to be crystalline with diameter of 122 nm, and CSD/TL exhibited marked improvement in the dissolution behavior as compared to crystalline TL. Under irradiation of UVA/B (250 W/m(2)), solution and amorphous solid dispersion of TL were found to be highly photodegradable, whereas high photochemical stability was seen in CSD/TL. After oral administration of CSD/TL, enhanced TL exposure was observed with increase of C(max) and AUC by 60- and 32-fold, respectively, as compared to crystalline TL. According to these observations, taken together with dissolution and pharmacokinetic behaviors, crystalline solid dispersion strategy would be efficacious to enhance bioavailability of TL with high photochemical stability.

Role of nanotechnology in pharmaceutical product development

A number of new molecular entities (NMEs) selected for full-scale development based on their safety and pharmacological data suffer from undesirable physicochemical and biopharmaceutical properties, which lead to poor pharmacokinetics and distribution after in vivo administration. An optimization of the preformulation studies to develop a dosage form with proper drug delivery system to achieve desirable pharmacokinetic and toxicological properties can aid in the accelerated development of these NMEs into therapies. Nanoparticulate drug delivery systems show a promising approach to obtain desirable druglike properties by altering the biopharmaceutics and pharmacokinetics properties of the molecule. Apart from the advantages of enhancing potential for systemic administration, nanoparticulate drug delivery systems can also be used for site-specific delivery, thus alleviating unwanted toxicity due to nonspecific distribution, improve patient compliance, and provide favorable clinical outcomes. This review summarizes some of the parameters and approaches that can be used to evaluate nanoparticulate drug delivery systems in early stages of formulation development.

Solubility and dissolution profile assessment in drug discovery

The purposes of the review are to: a) Provide a comprehensible introduction of the-state-of-the-art sciences of solubility and dissolution, b) introduce typical technologies to assess solubility and dissolution, and c) propose the best practice strategy. The theories of solubility and dissolution required in drug discovery were reviewed especially from the view point of oral absorption. The physiological conditions in the gastrointestinal fluid in humans and animals were then briefly summarized. Technologies to assess solubility and dissolution in drug discovery were then introduced. Recently, these technologies have been improved by the laboratory automation and computational technologies. Finally, the strategies to apply these technologies for a drug discovery project were discussed.

Molecular Interaction among Probucol/PVP/SDS Multicomponent System Investigated by Solid-State NMR

PURPOSE

Effects of polyvinylpyrrolidone (PVP) molecular weight on the solid-state intermolecular interactions among probucol/PVP/sodium dodecyl sulfate (SDS) ternary ground mixtures (GM) and the formation of nanoparticles were investigated by solid-state NMR spectroscopy.

MATERIALS AND METHODS

Ternary GMs of probucol were prepared with PVP (K12, K17, K30 or K90) and SDS at a weight ratio of 1:3:1 and were ground for 15, 30 and 60 min. Solid-state interactions were evaluated using powder X-ray diffraction (PXRD) and solid-state cross polarization/magic angle spinning (CP/MAS) (13)C NMR spectroscopy. A high resolution scanning electron microscopy (SEM) was employed to observe nanoparticles of probucol in the GM.

RESULTS

The solid-state (13)C CP/MAS NMR results indicate that the low molecular weight PVP interacts with probucol and SDS more strongly than the high molecular weight PVP in the ternary GM. This finding was consistent with the result that smaller drug nanoparticles were obtained using low molecular weight of PVP. SEM images of probucol/PVP K12/SDS confirmed the presence of nanoparticles (15-25 nm) in the GM.

CONCLUSIONS

Grinding-induced solid-state interactions among drug, PVP and SDS could be detected using solid state (13)C NMR. The interactions in both probucol-PVP and PVP-SDS should occur simultaneously to generate nanometer-sized particles of probucol.

Effect of particle size reduction on dissolution and oral absorption of a poorly water-soluble drug, cilostazol, in beagle dogs

The purpose of the present study was to investigate the effects of particle size on the dissolution and oral absorption of cilostazol. Three types of suspensions having different particle size distributions were prepared of the hammer-milled, the jet-milled cilostazol crystals and the NanoCrystal spray-dried powder of cilostazol. In vitro dissolution rate of cilostazol was significantly increased by reducing the particle size. The dissolution curves of the cilostazol suspensions were in good agreement with the simulation based on the Noyes-Whitney equation. The bioavailability of cilostazol after oral administration to dogs was increased with reducing the particle size. While positive food effect on the absorption was observed for the suspensions made of the hammer-milled and the jet-milled crystals, no significant food effect was found for the suspension made of the NanoCrystal cilostazol spray-dried powder. These results could be qualitatively predicted from the in vitro dissolution data using the bio-relevant media, FaSSIF and FeSSIF. In conclusion, the NanoCrystal technology is found to be efficient to improve the oral bioavailability of cilostazol and to avoid the food effect on the absorption.

Preparation and characterization of nanocrystals for solubility and dissolution rate enhancement of nifedipine

Poorly water-soluble drugs such as nifedipine (NIF) (approximately 20 microg/ml) offer challenging problems in drug formulation as poor solubility is generally associated to poor dissolution characteristics and thus to poor oral bioavailability. In order to enhance these characteristics, preparation of nifedipine nanoparticles has been achieved using high pressure homogenization. The homogenization procedure has first been optimized in regard to particle size and size distribution. Nanoparticles were characterized in terms of size, morphology and redispersion characteristics following water-removal. Saturation solubility and dissolution characteristics were investigated and compared to the un-milled commercial NIF to verify the theoretical hypothesis on the benefit of increased surface area. Crystalline state evaluation before and following particle size reduction was also conducted through differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) to denote eventual transformation to amorphous state during the homogenization process. Through this study, it has been shown that initial crystalline state is maintained following particle size reduction and that the dissolution characteristics of nifedipine nanoparticles were significantly increased in regards to the commercial product. The method being simple and easily scaled up, this approach should have a general applicability to many poorly water-soluble drug entities.

The role of biopharmaceutics in the development of a clinical nanoparticle formulation of MK-0869: a Beagle dog model predicts improved bioavailability and diminished food effect on absorption in human

MK-0869 (aprepitant), a potent substance P antagonist, is the active ingredient of EMEND which has recently been approved by the FDA for the prevention of chemotherapy-induced nausea and vomiting. Early clinical tablet formulations of MK-0869 showed significant food effects on absorption, suggesting that formulation could have a significant role in improving bioavailability. A Beagle dog model was developed in an effort to guide novel formulation development. Using the suspension of the micronized bulk drug used for the tablet formulations, the food effect on absorption was confirmed in the dog at a similar magnitude to that observed in humans. Further dog studies demonstrated a clear correlation between particle size and in vivo exposures, with the nanoparticle (NanoCrystal) colloidal dispersion formulation providing the highest exposure, suggesting dissolution-limited absorption. The NanoCrystal dispersion also eliminated the food effect on oral absorption in the dog at a dose of 2mg/kg. Regional absorption studies using triport dogs indicated that the absorption of MK-0869 was limited to the upper gastrointestinal tract. These results provided strong evidence that the large increase in surface areas of the drug nanoparticles could overcome the narrow absorption window and lead to rapid in vivo dissolution, fast absorption, and increased bioavailability. In addition, the dog model was used for optimizing formulation processes in which the nanoparticles were incorporated into solid dosage forms, and for selecting excipients to effectively re-disperse the nanoparticles from the dosage units. The human pharmacokinetic data using the nanoparticle formulation showed excellent correlations with those generated in the dog.

Micron-size drug particles: common and novel micronization techniques

Drug powders containing micron-size drug particles are used in several pharmaceutical dosage forms. Many drugs, especially newly developed substances, are poorly water soluble, which limits their oral bioavailability. The dissolution rate can be enhanced by using micronized drugs. Small drug particles are also required in administration forms, which require the drug in micron-size size due to geometric reasons in the organ to be targeted (e.g., drugs for pulmonary use). The common technique for the preparation of micron-size drugs is the mechanical comminution (e.g., by crushing, grinding, and milling) of previously formed larger particles. In spite of the widespread use of this technique, the milling process does not represent the ideal way for the production of small particles because drug substance properties and surface properties are altered in a mainly uncontrolled manner. Thus, techniques that prepare the drug directly in the required particle size are of interest. Because physicochemical drug powder properties are decisive for the manufacturing of a dosage form and for therapeutic success, the characterization of the particle surface and powder properties plays an important role. This article summarizes common and novel techniques for the production of a drug in small particle size. The properties of the resulting products that are obtained by different techniques are characterized and compared.

Enhancing the oral bioavailability of the poorly soluble drug dicumarol with a bioadhesive polymer

This article investigates the effect of particle size and the incorporation of a bioadhesive polymer, poly(fumaric-co-sebacic) anhydride p(FA:SA), on the relative bioavailability of dicumarol. A novel method was used to reduce particle size of the drug, and encapsulated formulations were fabricated using a phase inversion technique to produce nanospheres and microspheres with varying size. Groups of Yorkshire swine were catheterized and gavaged after fasting for 12 h with each formulation in a 50 mg/mL suspension. Blood was collected at different time points, from 0 to 96 h, and pharmacokinetic analysis revealed that formulations incorporating the smaller drug particles showed the highest bioavailability: micronized drug with 7% p(FA:SA) 17:83 polymer had 190% relative bioavailability, and phase inverted p(FA:SA) 17:83 microspheres with 31% (w/w) loading had 198% relative bioavailability to spray dried formulation. Formulations with larger drug particles achieved 71% relative bioavailability. A nonadhesive formulation, fabricated with poly(lactic acid) (PLA), showed 91% relative bioavailability. Both particle size and polymer composition play a role in oral absorption of dicumarol.

Nanoparticle formation of poorly water-soluble drugs from ternary ground mixtures with PVP and SDS

Poorly water-soluble drugs N-5159, griseofulvin (GFV), glibenclamide (GBM) and nifedipine (NFP) were ground in a dry process with polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS). Different crystallinity behavior of each drug during grinding was shown in the ternary Drug/PVP/SDS system. However, when each ternary Drug/PVP/SDS ground mixture was added to distilled water, crystalline nanoparticles which were 200 nm or less in size were formed and had excellent stability. Zeta potential measurement suggested that the nanoparticles had a structure where SDS was adsorbed onto the particles that were formed by the adsorption of PVP on the surface of drug crystals. Stable existence of crystalline nanoparticles was attributable to the inhibition of aggregation caused by the adsorption of PVP and SDS on the surface of drug crystals. Furthermore, the electrostatic repulsion due to the negative charge of SDS on a shell of nanoparticles could be assumed to contribute to the stable dispersion.

Novel benzoylurea derivatives as potential antitumor agents; synthesis, activities and structure-activity relationships

A series of pyrazoloxyphenyl benzoyl urea derivatives was designed and synthesized for cytotoxic evaluation as potential antitumor agents. The synthetic compounds were evaluated for in vitro cytotoxicity against five human tumor cell lines, including A-549, SKOV-3, SK-MEL-2, XF-498 and HCT-15. Among others, compound 11 exhibited 50-100 times greater antitumor activities than the commercial product, Cisplatin.

Formation of fine drug particles by cogrinding with cyclodextrins. I. The use of beta-cyclodextrin anhydrate and hydrate

PURPOSE

To improve the micromeritical properties of pranlukast (PRK) hydrate, a cogrinding process with cyclodextrin was used, and the formation of fine drug particles was investigated.

METHODS

PRK crystals were ground with either beta-cyclodextrin (beta-CD) anhydrate or beta-CD hydrate crystals at a mixing molar ratio of 2:1 (beta-CD:PRK) to prepare the ground mixtures (GMs). Powder X-ray diffraction measurement and particle size analysis were performed.

RESULTS

The two GMs differed from one another in appearance, wettability, and fine particle production. Quantitative determination demonstrated that when the beta-CD hydrate/PRK GM was dispersed in water, 96% of PRK loaded in GM became fine particles smaller than 0.8 microm. In contrast, only 1.4% of PRK in GM transformed to fine particles in the case of beta-CD anhydrate/PRK GM. The PRK fine particles were considered to be dispersed as small crystals. The stability of PRK particles in the aqueous solution was improved by the addition of a water-soluble polymer.

CONCLUSION

Cogrinding with a beta-CD of higher water content can be an effective method to prepare fine drug particles at the submicron level.

Theoretical predictions of drug absorption in drug discovery and development

The clinical development of new drugs is often terminated because of unfavourable pharmacokinetic properties such as poor intestinal absorption after oral administration. Intestinal permeability and solubility are two of the most important factors that determine the absorption properties of a compound. Efficient and reliable computational models that predict these properties as early as possible in drug discovery and development are therefore desirable. In this review, we first discuss the implementation of predictive models of intestinal drug permeability and solubility in drug discovery and development. Secondly, we discuss the mechanisms of intestinal drug permeability and computational methods that can be used to predict it. We then discuss factors influencing drug solubility and models for predicting it. We finally speculate that once these and other predictive computational models are implemented in drug discovery and development, these processes will become much more effective. Further, an increased fraction of drug candidates that are less likely to fail during clinical development will be selected.

Improvement of dissolution rates of poorly water soluble APIs using novel spray freezing into liquid technology

PURPOSE

To develop and demonstrate a novel particle engineering technology, spray freezing into liquid (SFL), to enhance the dissolution rates of poorly water-soluble active pharmaceutical ingredients (APIs).

METHODS

Model APIs, danazol or carbamazepine with or without excipients, were dissolved in a tetrahydrofuran/water cosolvent system and atomized through a nozzle beneath the surface of liquid nitrogen to produce small frozen droplets, which were subsequently lyophilized. The physicochemical properties of the SFL powders and controls were characterized by X-ray diffraction, scanning electron microscopy (SEM), particle size distribution, surface area analysis, contact angle measurement, and dissolution.

RESULTS

The X-ray diffraction pattern indicated that SFL powders containing either danazol or carbamazepine were amorphous. SEM micrographs indicated that SFL particles were highly porous. The mean particle diameter of SFL carbamazepine/SLS powder was about 7 microm. The surface area of SFL danazol/poloxamer 407 powder was 11.04 m2/g. The dissolution of SFL danazol/poloxamer 407 powder at 10 min was about 99%. The SFL powders were free flowing and had good physical and chemical stability after being stored at 25 degrees C/60%RH for 2 months.

CONCLUSIONS

The novel SFL technology was demonstrated to produce nanostructured amorphous highly porous particles of poorly water soluble APIs with significantly enhanced wetting and dissolution rates.

Formulation and antitumor activity evaluation of nanocrystalline suspensions of poorly soluble anticancer drugs

PURPOSE

Determine if wet milling technology could be used to formulate water insoluble antitumor agents as stabilized nanocrystalline drug suspensions that retain biological effectiveness following intravenous injection.

METHODS

The versatility of the approach is demonstrated by evaluation of four poorly water soluble chemotherapeutic agents that exhibit diverse chemistries and mechanisms of action. The compounds selected were: piposulfan (alkylating agent), etoposide (topoisomerase II inhibitor), camptothecin (topoisomerase I inhibitor) and paclitaxel (antimitotic agent). The agents were wet milled as a 2% w/v solids suspension containing 1% w/v surfactant stabilizer using a low energy ball mill. The size, physical stability and efficacy of the nanocrystalline suspensions were evaluated.

RESULTS

The data show the feasibility of formulating poorly water soluble anticancer agents as physically stable aqueous nanocrystalline suspensions. The suspensions are physically stable and efficacious following intravenous injection.

CONCLUSIONS

Wet milling technology is a feasible approach for formulating poorly water soluble chemotherapeutic agents that may offer a number of advantages over a more classical approach.

Improved oral absorption of enteric coprecipitates of a poorly soluble drug

An anticancer agent, N-[[[4-(5-bromo-2-pyrimidinyloxy)-3-chlorophenyl]amino]carbonyl]-2 - nitrobenzamide (HO-221, 1), shows poor oral absorption and is only slightly soluble in water (0.055 microgram/mL at 37 degrees C). The coprecipitates with polyvinylpyrrolidone or a vinylpyrrolidone and vinylacetate copolymer (copolyvidone) showed a marked increase of the dissolution rate and attainment of temporary supersaturation of 1. The oral bioavailability of these preparations in dogs at a dose of 1 of 5 mg/kg was approximately 60%, which was 3.5 times greater than that of a micronized preparation. Further, the enteric coprecipitate with hydroxypropyl methylcellulose phthalate 200731, which showed a dissolution profile similar to that of the copolyvidone preparation at pH 6.5 but no dissolution at pH 1.2, revealed the almost complete oral absorption. Because intraduodenal administration of the copolyvidone coprecipitate showed a higher absorption than that of per oral administration, it was suggested that the partial precipitation of crystallites in the nonenteric coprecipitates occurred before reaching the absorption site, the small intestine.