Improved oral absorption of enteric coprecipitates of a poorly soluble drug

Molecular Dynamics and Diffusion in Amorphous Solid Dispersions Containing Imidacloprid

The main goal of this study is to develop an experimental toolbox to estimate the self-diffusion coefficient of active ingredients (AI) in single-phase amorphous solid dispersions (ASD) close to the glass transition of the mixture using dielectric spectroscopy (DS) and oscillatory rheology. The proposed methodology is tested for a model system containing the insecticide imidacloprid (IMI) and the copolymer copovidone (PVP/VA) prepared via hot-melt extrusion. For this purpose, reorientational and the viscoelastic structural (α-)relaxation time constants of hot-melt-extruded ASDs were obtained via DS and shear rheology, respectively. These were then utilized to extract the viscosity as well as the fragility index of the dispersions as input parameters to the fractional Stokes-Einstein (F-SE) relation. Furthermore, a modified version of Almond-West (AW) formalism, originally developed to describe charge diffusion in ionic conductors, was exercised on the present model system for the estimation of the AI diffusion coefficients based on shear modulus relaxation times. Our results revealed that, at the calorimetric glass-transition temperature (T_g), the self-diffusion coefficients of the AI in the compositional range from infinite dilution up to 60 wt % IMI content lied in the narrow range of 10^-18-10^-20 m² s^-1, while the viscosity values of the dispersions at T_g varied between 10⁸ Pa s and 10¹⁰ Pa s. In addition, the phase diagram of the IMI-PVP/VA system was determined using the melting point depression method via differential scanning calorimetry (DSC), while mid-infrared (IR) spectroscopy was employed to investigate the intermolecular interactions within the solid dispersions. In this respect, the findings of a modest variation in melting point at different compositions stayed in agreement with the observations of weak hydrogen bonding interactions between the AI and the polymer. Moreover, IR spectroscopy showed the intermolecular IMI-IMI hydrogen bonding to have been considerably suppressed, as a result of the spatial separation of the AI molecules within the ASDs. In summary, this study provides experimental approaches to study diffusivity in ASDs using DS and oscillatory rheology, in addition to contributing to an enhanced understanding of the interactions and phase behavior in these systems.

Super Bioavailable Itraconazole and Its Place and Relevance in Recalcitrant Dermatophytosis: Revisiting Skin Levels of Itraconazole and Minimum Inhibitory Concentration Data

Itraconazole, is the most commonly prescribed oral antifungal agent in India, and has a low minimum inhibitory concentration as compared to other oral antifungals, and in conjunction with the markedly high skin levels, the drug should have a predictably good clinical response which is not the consistent experience of clinicians. Probably the variation in pelletization parameters might affect the bioavailability of the drug and consequently affect the serum levels. The maximum bioavailability of conventional itraconazole is 55 percent, which is neither consistent nor predictable. However, the novel itraconazole (Super bioavailable Itraconazole) with targeted drug release in the small intestine has predictable serum levels with minimum interindividual variability, which could make it a potentially useful drug in recalcitrant dermatophytosis.

Novel thymoquinone lipidic core nanocapsules with anisamide-polymethacrylate shell for colon cancer cells overexpressing sigma receptors

The biggest challenge in colorectal cancer therapy is to avoid intestinal drug absorption before reaching the colon, while focusing on tumor specific delivery with high local concentration and minimal toxicity. In our work, thymoquinone (TQ)-loaded polymeric nanocapsules were prepared using the nanoprecipitation technique using Eudragit S100 as polymeric shell. Conjugation of anisamide as a targeting ligand for sigma receptors overexpressed by colon cancer cells to Eudragit S100 was carried out via carbodiimide coupling reaction, and was confirmed by thin layer chromatography and ¹H-NMR. TQ nanocapsules were characterized for particle size, surface morphology, zeta potential, entrapment efficiency % (EE%), in vitro drug release and physical stability. A cytotoxicity study on three colon cancer cell lines (HT-29, HCT-116, Caco-2) was performed. Results revealed that the polymeric nanocapsules were successfully prepared, and the in vitro characterization showed a suitable size, zeta potential, EE% and physical stability. TQ exhibited a delayed release pattern from the nanocapsules in vitro. Anisamide-targeted TQ nanocapsules showed higher cytotoxicity against HT-29 cells overexpressing sigma receptors compared to their non-targeted counterparts and free TQ after incubation for 48 h, hence delineating anisamide as a promising ligand for active colon cancer targeting.

Design And Characterisation Of Novel Sorafenib-Loaded Carbon Nanotubes With Distinct Tumour-Suppressive Activity In Hepatocellular Carcinoma

PURPOSE

Over the past 30 years, no consistent survival benefits have been recorded for anticancer agents of advanced hepatocellular carcinoma (HCC), except for the multikinase inhibitor sorafenib (Nexavar®), which clinically achieves only ~3 months overall survival benefit. This modest benefit is attributed to limited aqueous solubility, slow dissolution rate and, consequently, limited absorption from the gastrointestinal tract. Thus, novel formulation modalities are in demand to improve the bioavailability of the drug to attack HCC in a more efficient manner. In the current study, we aimed to design a novel sorafenib-loaded carbon nanotubes (CNTs) formula that is able to improve the therapeutic efficacy of carried cargo against HCC and subsequently investigate the antitumour activity of this formula.

MATERIALS AND METHODS

Sorafenib was loaded on functionalized CNTs through physical adsorption, and an alginate-based method was subsequently applied to microcapsulate the drug-loaded CNTs (CNTs-SFN). The therapeutic efficacy of the new formula was estimated and compared to that of conventional sorafenib, both in vitro (against HepG2 cells) and in vivo (in a DENA-induced HCC rat model).

RESULTS

The in vitro MTT anti-proliferative assay revealed that the drug-loaded CNTs formula was at least two-fold more cytotoxic towards HepG2 cells than was sorafenib itself. Moreover, the in vivo animal experiments proved that our innovative formula was superior to conventional sorafenib at all assessed end points. Circulating AFP-L3% was significantly decreased in the CNTs-SFN-MCs-treated group (14.0%) in comparison to that of the DENA (40.3%) and sorafenib (38.8%) groups. This superiority was further confirmed by Western blot analysis and immunofluorescence assessment of some HCC-relevant biomarkers.

CONCLUSION

Our results firmly suggest the distinctive cancer-suppressive nature of CNTs-SFN-MCs, both against HepG2 cells in vitro and in a DENA-induced HCC rat model in vivo, with a preferential superiority over conventional sorafenib.

Parameters that determine dissolution and efficacy of itraconazole and its relevance to recalcitrant dermatophytoses

INTRODUCTION

Recalcitrant dermatophytoses is on the rise. Though myriad factors contribute to recalcitrance including terbinafine resistance, itraconazole largely remains sensitive. However, there are increasing instances of patients not responding adequately to itraconazole despite low MICs, probably due to issues plaguing the pelletization process, resulting in suboptimal quality. Data on this topic was searched on pubmed using the search items: itraconazole, MIC, MFC, quality, assay, pharmacokinetics, pharmacodynamics, dermatophytoses, and recalcitrance. Areas covered: A detailed analysis of the manufacturing process of itraconazole with emphasis on pelletization and parameters affecting the dissolution and bioavailability is presented. Important formulation factors including drug-polymer ratio, polymer type, coating thickness, bead size, and number are discussed. Also covered is the rationale of dosimetry of itraconazole in dermatophytoses based on the skin pharmacokinetics and MIC of the organism. Expert opinion: The process of pelletization has multiple components aiming to achieve maximum dissolution of the drug. Variations in the process, pellet quality, number, and polymer determine absorption. Morphometric analysis of pellets is a simple method to quantify quality of the drug. Once the process has been standardized, dosimetry depends on the route of secretion and site of infection, accounting for the variation of doses from 100 mg to 400 mg/day.

Development, current applications and future roles of biorelevant two-stage in vitro testing in drug development

Objectives

Various types of two stage in vitro testing have been used in a number of experimental settings. In addition to its application in quality control and for regulatory purposes, two-stage in vitro testing has also been shown to be a valuable technique to evaluate the supersaturation and precipitation behavior of poorly soluble drugs during drug development.

Key findings

The so-called ‘transfer model’, which is an example of two-stage testing, has provided valuable information about the in vivo performance of poorly soluble, weakly basic drugs by simulating the gastrointestinal drug transit from the stomach into the small intestine with a peristaltic pump. The evolution of the transfer model has resulted in various modifications of the experimental model set-up. Concomitantly, various research groups have developed simplified approaches to two-stage testing to investigate the supersaturation and precipitation behavior of weakly basic drugs without the necessity of using a transfer pump.

Summary

Given the diversity among the various two-stage test methods available today, a more harmonized approach needs to be taken to optimize the use of two stage testing at different stages of drug development.

Population pharmacokinetic modeling of itraconazole and hydroxyitraconazole for oral SUBA-itraconazole and sporanox capsule formulations in healthy subjects in fed and fasted states

Itraconazole is an orally active antifungal agent that has complex and highly variable absorption kinetics that is highly affected by food. This study aimed to develop a population pharmacokinetic model for itraconazole and the active metabolite hydroxyitraconazole, in particular, quantifying the effects of food and formulation on oral absorption. Plasma pharmacokinetic data were collected from seven phase I crossover trials comparing the SUBA-itraconazole and Sporanox formulations of itraconazole. First, a model of single-dose itraconazole data was developed, which was then extended to the multidose data. Covariate effects on itraconazole were then examined before extending the model to describe hydroxyitraconazole. The final itraconazole model was a 2-compartment model with oral absorption described by 4-transit compartments. Multidose kinetics was described by total effective daily dose- and time-dependent changes in clearance and bioavailability. Hydroxyitraconazole was best described by a 1-compartment model with mixed first-order and Michaelis-Menten elimination for the single-dose data and a time-dependent clearance for the multidose data. The relative bioavailability of SUBA-itraconazole compared to that of Sporanox was 173% and was 21% less variable between subjects. Food resulted in a 27% reduction in bioavailability and 58% reduction in the transit absorption rate constant compared to that with the fasted state, irrespective of the formulation. This analysis presents the most extensive population pharmacokinetic model of itraconazole and hydroxyitraconazole in the literature performed in healthy subjects. The presented model can be used for simulating food effects on itraconazole exposure and for performing prestudy power analysis and sample size estimation, which are important aspects of clinical trial design of bioequivalence studies.

Evaluation of a nanoemulsion formulation strategy for oral bioavailability enhancement of danazol in rats and dogs

The objective of this study was to determine whether nanoemulsion formulations constitute a viable strategy to improve the oral bioavailability of danazol, a compound whose poor aqueous solubility limits its oral bioavailability. Danazol-containing oil-in-water nanoemulsions (NE) with and without cosurfactants stearylamine (SA) and deoxycholic acid (DCA) were prepared and characterized. Nanoemulsion droplets size ranging from 238 to 344 nm and with surface charges of -24.8 mV (NE), -26.5 mV (NE-DCA), and +27.8 mV (NE-SA) were reproducibly obtained. Oral bioavailability of danazol in nanoemulsions was compared with other vehicles such as PEG400, 1% methylcellulose (MC) in water (1% MC), Labrafil, and a Labrafil/Tween 80 (9:1) mixture, after intragastric administration to rats and after oral administration of NE-SA, a Labrafil solution, or a Danocrine® tablet to dogs. The absolute bioavailability of danazol was 0.6% (PEG400), 1.2% (1% MC), 6.0% (Labrafil), 7.5% (Labrafil/Tween80), 8.1% (NE-DCA), 14.8% (NE), and 17.4% (NE-SA) in rats, and 0.24% (Danocrine), 6.2% (Labrafil), and 58.7% (NE-SA) in dogs. Overall, danazol bioavailability in any nanoemulsion was higher than any other formulation. Danazol bioavailability from NE and NE-SA was 1.8- to 2.2-fold higher than NE-DCA nanoemulsion and could be due to significant difference in droplet size.

A new protocol to determine the solubility of drugs into polymer matrixes

In this paper we present a new protocol to determine faster the solubility of drugs into polymer matrixes. The originality of the method lies in the fact that the equilibrium saturated states are reached by demixing of supersaturated amorphous solid solutions and not by dissolution of crystalline drug into the amorphous polymer matrix as for usual methods. The equilibrium saturated states are thus much faster to reach due to the extra molecular mobility resulting from the strong plasticizing effect associated with the supersaturation conditions. The method is validated using the indomethacin/polyvinylpyrrolidone mixture whose solubility diagram was previously determined by usual techniques. The supersaturated states have been directly obtained in the solid state by comilling, and the investigations have been performed by differential scanning calorimetry and powder X-ray diffraction.

Fusion processing of itraconazole solid dispersions by kinetisol dispersing: a comparative study to hot melt extrusion

KinetiSol Dispersing (KSD) is a novel high energy manufacturing process investigated here for the production of pharmaceutical solid dispersions. Solid dispersions of itraconazole (ITZ) and hypromellose were produced by KSD and compared to identical formulations produced by hot melt extrusion (HME). Materials were characterized for solid state properties by modulated differential scanning calorimetry and X-ray diffraction. Dissolution behavior was studied under supersaturated conditions. Oral bioavailability was determined using a Sprague-Dawley rat model. Results showed that KSD was able to produce amorphous solid dispersions in under 15 s while production by HME required over 300 s. Dispersions produced by KSD exhibited single phase solid state behavior indicated by a single glass transition temperature (T(g)) whereas compositions produced by HME exhibited two T(g)s. Increased dissolution rates for compositions manufactured by KSD were also observed compared to HME processed material. Near complete supersaturation was observed for solid dispersions produced by either manufacturing processes. Oral bioavailability from both processes showed enhanced AUC compared to crystalline ITZ. Based on the results presented from this study, KSD was shown to be a viable manufacturing process for the production of pharmaceutical solid dispersions, providing benefits over conventional techniques including: enhanced mixing for improved homogeneity and reduced processing times.

Amorphous compositions using concentration enhancing polymers for improved bioavailability of itraconazole

Amorphous engineered particle compositions of itraconazole (ITZ) and potential concentration enhancing polymers, cellulose acetate phthalate (CAP) and polyvinyl acetate phthalate (PVAP), were produced by ultra-rapid freezing to investigate the effect of these polymers on the bioavailability of ITZ solid dispersions. X-ray diffraction analyses of engineered particle compositions were shown to be amorphous. Modulated differential scanning calorimetry demonstrated that ITZ:CAP engineered particle compositions exhibited a strong correlation with the Gordon-Taylor relationship while ITZ:PVAP formulations exhibited positive deviations from predicted values attributed to hydrogen bonding interactions between the drug and polymer. Energy dispersive spectroscopy mapping demonstrated that the drug was homogenously distributed within all compositions, supporting the miscibility of the drug with the polymers. Scanning electron microscopy imaging of the particles demonstrated that the material existed in two general forms, discrete particles of approximately 5 microm and larger aggregates in excess of 30 microm, with engineered particle compositions having approximately 15 times higher measured specific surfaces areas compared to micronized ITZ. In vitro supersaturated dissolution results showed that all compositions provided significantly lower levels of supersaturation in acidic media and greater extents of supersaturation in neutral media compared to Sporanox pellets. ITZ: CAP formulations provided the greatest degree and extent of supersaturation in neutral media. Dissolution data were fitted to an exponential relationship based on a simplified model of particle growth, allowing for the determination of drug half-life in solution for evaluation of stabilization behavior. 1:2 ITZ:CAP showed superior in vitro performance compared to all other engineered particle compositions and was selected for in vivo testing. Although not fully elucidated, data indicated that the stabilization mechanism was due to interactions between the drug and polymer, primarily attributed to steric hindrance resulting from the molecular weight of the polymer chain and chemical composition of the polymer backbone relative to position of hydrogen bonding sites. In vivo testing conducted in Sprague-Dawley rats (n = 6) demonstrated a significant improvement in oral bioavailability from the 1:2 ITZ:CAP (AUC = 4,516 +/- 1,949 ng x h/mL) compared to the Sporanox pellets (AUC = 2,132 +/- 1,273 ng x h/mL) (p < or = 0.05). Additionally, the more rapid onset of action indicated superior targeting of the upper small intestines, and the prolonged half-life suggested the utility of CAP to maintain supersaturated concentrations, in vivo. These results demonstrated that amorphous compositions of ITZ and enteric concentration enhancing polymers provided improved bioavailability due to enhanced intestinal targeting and increased durations of supersaturation.

Preparation and Characterization of Solid Dispersions of Dipyridamole with a Carrier “Copolyvidonum Plasdone®S-630”

Solid dispersions (SDs) of dipyridamole (DIP) with a novel carrier copolyvidonum Plasdone S-630 (CoPVP) were developed by solvent evaporation method. The solid state of SDs of DIP with CoPVP (SDs CoPVP) was characterized by fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarizing microscopy, compared with that of SDs of DIP with polyvinylpyrrolidone Plasdone K-29/32 (SDs PVP). FT-IR analysis demonstrated the presence of intermolecular hydrogen bonding between DIP and CoPVP or PVP in SDs. DSC and XRD studies indicated that DIP presented in amorphous state in both SDs CoPVP and SDs PVP at higher weight ratios. The dissolution property of SDs CoPVP was significantly improved in comparison of pure DIP and physical mixtures with CoPVP (PM CoPVP). Both SDs CoPVP and SDs PVP powder showed the favorable flowability. However, SDs CoPVP showed better compressibility than SDs PVP. The lower hydroscopicity of SDs CoPVP could be advantageous to the stability to SDs. This study proves the potential of CoPVP as a carrier in the formulations of SDs for poorly soluble drugs.

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.

Bioavailability of the amino acid-attached prodrug as a new anti-HIV agent in rats

The primary objective of this study was to compare the pharmacokinetics of a new anti-human immunodeficiency virus agent 1-(2-amino-pyridin-4-ylmethyl)-6-(3,5-dimethyl-benzoyl)-5-isopropyl-1H-pyrimidine-2,4-dione (VP-0502) with its amino acid prodrug alanine amide of VP-0502 (VP-0502AL), following intravenous and oral administrations to rats. The plasma concentrations of both analytes were analyzed via high-performance liquid chromatography coupled with photodiode-array detection (HPLC-DAD). When VP-0502 was intravenously administered at 20 mg/kg, the analyte appeared in low levels with an AUC of 0.3 µg · h/ml, and C₀ of 0.2 µg/ml in plasma. However, both the prodrug VP-0502AL and its metabolite VP-0502 appeared at comparatively higher levels following intravenous injection of VP-0502AL at the same dose. VP-0502AL's pharmacokinetic parameters were V_d: 4.6 l/kg; AUC: 3 µg · h/ml; t_1/2: 0.5 h; C₀: 6 µg/ml; CL_tot: 7 l/h/kg; and MRT: 0.6 h. Following oral administration of VP-0502 (100 mg/kg), it was not detectable in plasma (<50 ng/ml), while after the oral administration of VP-0502AL, VP-0502 was quantitatively detected as an active metabolite for the first 7 h, with a maximum plasma concentration (C_max) of 0.8 µg/ml, and an area under the concentration-time curve (AUC) of 2 µg · h/ml. The oral pharmaco-kinetic parameters of VP-0502AL were calculated to be: maximum concentration time (t_max) 2.7 h; C_max 0.2 µg/ml; elimination half-life (t_1/2): 0.8 h; and AUC 0.5 µg · h/ml. Overall the findings indicate that VP-0502AL has a favorable pharmacokinetic profile as a prodrug with rapid transformation into the active metabolite, and that the attachment of the amino acid alanine to VP-0502 is an effective approach to improve its oral bioavailability. VP-0502AL is predicted to become a new highly bioavailable anti-AIDS drug candidate and/or lead compound.

Solid dispersions of itraconazole and enteric polymers made by ultra-rapid freezing

The primary objective of the study is to investigate the influence of composition parameters including drug:polymer ratio and polymer type, and particle structure of enteric solid dispersions on the release of ITZ under sink and supersaturated dissolution conditions. Modulated differential scanning calorimetry (MDSC) was utilized to define the level of ITZ miscibility with each polymer. The compositions were completely miscible at 60% ITZ for both polymers and as high as 70% in HP-55. High potency composition glass transition temperatures (T(g)) correlated with predicted T(g)'s from the Gordon-Taylor equation, however, recrystallization exotherms revealed pure amorphous regions indicating that phase separation occurred during particle formation. Furthermore, in vitro studies including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), surface area analysis (BET), and dissolution were performed to determine differences between low potency (completely miscible) and high potency (partially miscible) compositions. Dissolution studies on low potency ITZ compositions revealed that miscibility plays an active role in ITZ release under sink conditions, and square root diffusion through the enteric polymer is observed. Supersaturated dissolution profiles revealed high potency compositions had maximum saturation levels (C/Ceq(max)) between 10.6- and 8-times equilibrium solubility, but had higher cumulative extents of supersaturation, compared to low potency compositions which had C/Ceq(max) values of 15-19.6. However, these low potency compositions rapidly precipitated leading to significantly lower AUCs (p<0.05). The change in the miscibility of the solid dispersion had a pronounced effect of drug release (sink) while differences in potency influenced supersaturated dissolution profiles.

Enhancement of the dissolution and permeation rates of meloxicam by formation of its freeze-dried solid dispersions in polyvinylpyrrolidone K-30

Freeze-drying (FD) and solvent evaporation (SE) were used to prepare solid dispersions (SDs) of meloxicam (MX) in polyvinylpyrrolidone K-30 (PVP). The SDs were prepared at different ratios, namely 1:1, 1:3, and 1:5 MX:PVP weight ratio. Differential scanning calorimetry (DSC), infrared absorption spectroscopy (IR), and x-ray powder diffractometry (XPD) were utilized to characterize the physicochemical properties of the SDs. Meloxicam (MX) in the solid dispersions appeared with less crystallinity form and was present in a complete amorphous form at higher PVP ratio. Dissolution rates of MX as a pure drug, physical mixtures (PMs), and SDs indicated a marked increase of the dissolution rate of MX in presence of PVP. The increase in the dissolution rate was dependent on the ratio of PVP and the method of preparation. In addition, the permeability of the drug through standard cellophane membrane and hairless mouse skin was also evaluated. The permeation rate of MX was significantly increased in the case of SDs and was dependent on the ratio of PVP. The results were primarily due to increase wettability, the solubilization of the drug by the carrier, and formation of MX amorphous form.

Solvent change co-precipitation with hydroxypropyl methylcellulose phthalate to improve dissolution characteristics of a poorly water-soluble drug

Research compound GWX belongs to biopharmaceutical classification system type II, and hence shows dissolution-rate-limited absorption. To improve its dissolution performance, GWX was formulated as a co-precipitate with hydroxypropyl methylcellulose phthalate (HPMCP). Co-precipitates with various drug-HPMCP ratios were prepared and characterised using modulated differential scanning calorimetry (MDSC), X-ray powder diffraction, HPLC and dissolution testing. Co-precipitates with 1:9 and 2:8 drug-HPMCP ratios showed the highest extent of dissolution after both 5 and 90 min, followed by 3:7, 4:6, and 5:5 drug-HPMCP co-precipitates, in respective order. Co-precipitates with drug-HPMCP ratios of 6:4 and greater showed no significant improvement in dissolution over crystalline drug alone. The amounts of crystalline and amorphous drug in co-precipitates, as determined by MDSC, and HPLC quantification of the total amount of drug in co-precipitates were used to determine the amount of drug incorporated into solid solution. It was found that dissolution rate and extent was correlated to the amount of drug incorporated into amorphous solid solution for the 1:9 to 5:5 drug-HPMCP ratio co-precipitates. Amorphous drug alone and physical mixtures of drug and HPMCP showed very little and no significant improvement in dissolution rate or extent, respectively, above crystalline drug alone. Amorphous drug alone re-crystallized to a large extent within 1 min of contact with the dissolution medium, whereas 4:6 drug-HPMCP co-precipitate showed a lower degree of re-crystallization and 2:8 drug-HPMCP co-precipitate showed very little re-crystallization. It was concluded that the likely mechanisms of improved dissolution of low drug-HPMCP ratio co-precipitates were improved wetting or increased surface area for mass transfer, thermodynamically enhanced dissolution of a higher energy amorphous form and inhibition of re-crystallization, when drug was incorporated into solid solution.

Solubility of solid dispersions of pizotifen malate and povidone

We analyzed the physicochemical characteristics of solid dispersions of pizotifen malate and povidone (Kollidon 12) at different proportions; we used X-ray diffraction, infrared spectrometry and differential scanning calorimetry (DSC) and tested the solubility of the solid dispersions in equilibrium. The results were compared with findings for physical mixtures with the same proportions. A solid dispersion with a drug proportion of 16%-17% formed a eutectic mixture. Solubility of pizotifen malate increased with the proportion of drug in the solid dispersion up to a drug:polymer ratio of 40:60. The hydrotropic effect of the polymer also favored solubility: In physical mixtures, this effect was greatest at a drug:polymer ratio of 10:90; solubility at this proportion was equal to that of the solid dispersion at the same proportion.

Physicochemical properties of amorphous precipitates of cimetidine-indomethacin binary system

We have found that the binary system, consisting of a precipitate of cimetidine and naproxen, became amorphous due to intermolecular interaction. In order to clarify the interaction between cimetidine and other drugs, the physicochemical properties of binary systems consisting of cimetidine and drugs, phenacetin, salicylamide or indomethacin, were investigated. X-ray powder diffraction patterns and thermal analysis findings for the precipitates indicated that the cimetidine-indomethacin system has an amorphous structure, whereas the cimetidine-phenacetin and cimetidine-salicylamide systems do not. Fourier-transform infra-red (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy findings suggested that there is an intermolecular interaction between a proton in the imidazole ring of cimetidine and the C=O in the COOH of indomethacin. Since an interaction by the hydrogen bond between cimetidine and indomethacin would prevent three-dimensional arrangements of the molecules, the precipitate would be amorphous. In the cimetidine-indomethacin system, decarboxylation of indomethacin occurred below the melting temperature, indicating that the chemical stability decreased upon precipitation. Cimetidine was found to interact with drugs with a carboxyl group. The interaction would be applicable to make the amorphous system of the drugs and increase the solubility of the drugs.

Relative bioavailability of danazol in dogs from liquid-filled hard gelatin capsules

Danazol was dissolved in non-aqueous mixtures containing either polyethylene glycol 400 or polysorbate 80, and filled into hard gelatin capsules at 50 mg concentrations. The bioavailability of these formulations was compared with commercial danazol capsules in a two-way crossover study using young female beagle dogs. Both formulations showed greater oral bioavailability when compared with either the 100 or 200 mg commercial brand of danazol. The bioavailability of the polyethylene glycol 400 and polysorbate 80 formulations was enhanced 3.7 and 15.8 times, respectively, when compared at the 100 mg dose level.

Improving the oral bioavailability of albendazole in rabbits by the solid dispersion technique

We have investigated the oral bioavailability of granules of albendazole, a drug used for treating echinococcosis in man, prepared by the solid dispersion technique. Rapid dissolution and supersaturation were observed when hydroxypropylmethylcellulose and hydroxypropylmethylcellulose phthalate were used as carriers in the solid dispersion. They inhibited the crystallization of albendazole from the supersaturated solution and maintained an amorphous state for 8 h. Gastric acidity-controlled rabbits were used to evaluate the variation in absorption after oral administration of the albendazole solid dispersion. For rabbits with low gastric acidity the bioavailability of orally administered albendazole in the granular form prepared by solid dispersion was more than three times that of albendazole in physical mixtures. These results suggest that the bioavailability of albendazole in solid dispersions might be high even if there is a great variation in the gastric pH of patients.

Pharmacokinetics of a novel HIV-1 protease inhibitor incorporated into biodegradable or enteric nanoparticles following intravenous and oral administration to mice

CGP 57813 is a peptidomimetic inhibitor of human immunodeficiency virus type 1 (HIV-1) protease. This lipophilic compound was successfully entrapped into poly(D,L-lactic acid) (PLA) and pH sensitive methacrylic acid copolymers nanoparticle. The intravenous administration to mice of PLA nanoparticles loaded with CGP 57813 resulted in a 2-fold increase of the area under the plasma concentration-time curve, compared to a control solution. An increase in the elimination half-life (from 13 to 61 min) and in the apparent volume of distribution (1.7-3.6 L/kg) was observed for the nanoparticle incorporated compound vs control solution. Following oral administration, only nanoparticles made of the methacrylic acid copolymer soluble at low pH provided sufficient plasma levels of CGP 57813. In vitro, these nanoparticles dissolved completely within 5 min at pH 5.8. PLA nanoparticles, which are insoluble in the gastrointestinal tract, did not provide significant plasma concentrations of CGP 57813. From these observations, one can conclude that the passage of intact PLA nanoparticles across the gastrointestinal mucosa appears to be very low.