Solid State and Dissolution Rate Characterization of Co-Ground Mixtures of Nifedipine and Hydrophilic Carriers

Evaluating the solubility of compounds intended for intramammary infusion based upon tests conducted across a range of milk matrices

The ability to evaluate drug solubility in milk and milk-related products has relevance both to human and veterinary medicine. Model compounds explored in a previous investigation focused on drug solubility assessments when delivered in milk-associated vehicles for administration to human patients. In the current investigation, we focus on the solubility of drugs intended for delivery via intramammary infusion to cattle. Because there are logistic challenges typically associated with obtaining raw milk samples for these tests, there is a need to determine potential alternative media as a substitute for raw bovine milk. Given the complexity of the milk matrix, aqueous media do not reflect the range of factors that could impact these solubility assessments. This led to the current effort to explore the magnitude of differences that might occur when substituting raw bovine milk with off-the-shelf milk products such as whole milk, skim milk, or reconstituted whole milk powder. We considered conclusions based upon the solubility assessments derived from the use of the model compounds studied in our previous report and compared them to conclusions obtained when testing two drugs with differing physicochemical characteristics that are approved for administration via bovine intramammary infusion: cephapirin benzathine and cephapirin sodium. Based upon these results, we recommend that whole milk or reconstituted whole milk can substitute for bovine raw milk for the solubility assessment of compounds intended for administration via intramammary infusion. However, unlike the human drug situation, these tests should be conducted at 38°C.

Comparison study of physicochemical and biopharmaceutics properties of hydrophobic drugs ground by two dry milling processes

1. AbstractThis study focuses on the dry milling of BCS (Biopharmaceutical Classification System) class II molecules. These molecules have a limited bioavailability because of their low aqueous solubility, poor water wettability and low dissolution rate. In order to improve these properties, indomethacin (IND) and niflumic acid (NIF) were milled using two different types of equipment: Pulverisette 0® and CryoMill®. Milled samples were characterized and compared to commercial molecules. IND shows a modified solid state, like surface crystallinity reduction and an increase in water vapor adsorption from to 2 up to 5-fold due to milling processes. The obtained solubility data resulted in an improvement in solubility up to 1.2-fold and an increase in initial dissolution kinetics: 2% of dissolved drug for original crystals against 25% for milled samples. For NIF no crystallinity reduction, no change of surface properties and no solubility improvement after milling were noticed. In addition, milled particles seemed more agglomerated resulting in no changes in dissolution rate compared to the original drug. IND solubility and dissolution enhancement can be attributed to the modification of surface area, drug crystallinity reduction and water sorption increase due to specific behaviour related to the drug crystal disorder induced by milling process.

Intratracheally Inhalable Nifedipine-Loaded Chitosan-PLGA Nanocomposites as a Promising Nanoplatform for Lung Targeting: Snowballed Protection via Regulation of TGF-β/β-Catenin Pathway in Bleomycin-Induced Pulmonary Fibrosis

Pulmonary fibrosis is a serious ailment that may progress to lung remodeling and demolition, where the key participants in its incidence are fibroblasts responding to growth factors and cellular calcium swinging. Calcium channel blockers, like nifedipine (NFD), may represent auspicious agents in pulmonary fibrosis treatment. Unfortunately, NFD bears complicated pharmacodynamics and a diminished systemic bioavailability. Thus, the current study aimed to develop a novel, non-invasive nanoplatform for NFD for direct/effective pulmonary targeting via intratracheal instillation. A modified solvent emulsification–evaporation method was adopted for the fabrication of NFD-nanocomposites, integrating poly(D,L-lactide-co-glycolide) (PLGA), chitosan (CTS), and polyvinyl alcohol, and optimized for different physiochemical properties according to the 3² full factorial design. Additionally, the aerodynamic behavior of the nanocomposites was scrutinized through cascade impaction. Moreover, the pharmacokinetic investigations were conducted in rats. Furthermore, the optimum formulation was tested in bleomycin-induced pulmonary fibrosis in rats, wherein fibrotic and oxidative stress parameters were measured. The optimum nanocomposites disclosed a nanosized spherical morphology (226.46 nm), a high entrapment efficiency (61.81%) and a sustained release profile over 24 h (50.4%). As well, it displayed a boosted in vitro lung deposition performance with a mass median aerodynamic diameter of 1.12 µm. Pharmacokinetic studies manifested snowballed bioavailability of the optimal nanocomposites by 3.68- and 2.36-fold compared to both the oral and intratracheal suspensions, respectively. The intratracheal nanocomposites revealed a significant reduction in lung fibrotic and oxidative stress markers notably analogous to normal control besides repairing abnormality in TGF-β/β-catenin pathway. Our results conferred a compelling proof-of-principle that NFD-CTS-PLGA nanocomposites can function as a promising nanoparadigm for pulmonary fibrosis management.

In vitro and in vivo Evaluation of Ibuprofen Nanosuspensions for Enhanced Oral Bioavailability

INTRODUCTION

The objectives were to prepare, characterize, and evaluate different ibuprofen (IBU) nanosuspensions.

METHODS

The nanosuspensions produced by ultrahomogenization were compared with a marketed IBU suspension for particle size, in vitro dissolution, and in vivo absorption. Five groups of rabbits were orally administered with 25 mg/kg of IBU nanosuspension, nanoparticles, unhomogenized suspension, marketed product, and untreated suspension. A sixth group received 5 mg/kg IBU intravenously. Blood samples obtained were analyzed by chromatography.

RESULTS

The nanosuspensions showed significant decrease in particle size. Polyvinylpyrrolidone (PP) K30 profoundly increased aqueous solubility of IBU. Addition of Tween 80 (TW), in equal amount as PP (IBU:PP:TW, 1:2:2 w/w), resulted in much smaller particle size and better dissolution rate. The Cmax values achieved were 14.8 ± 1.64, 11.1 ± 1.37, 9.01 ± 0.761, 7.03 ± 1.38, and 3.23 ± 1.03 μg/mL, and the tmax values were 36 ± 8.2, 39 ± 8.2, 100 ± 17.3, 112 ± 15, and 105 ± 17 min for the nanosuspension, nanoparticle, unhomogenized suspension, marketed IBU suspension, and untreated IBU suspension in water, respectively. Bioavailability of the different formulations relative to the marketed suspension was found to be in the following sequence: nanosuspension > unhomogenized suspension > nanoparticles > untreated IBU suspension.

CONCLUSION

IBU/PP/TW nanosuspension showed enhanced in vitro and in vivo performance as compared to the marketed product. Nanosuspensions prepared by the ultrahigh-pressure homogenization technique can be used as a good formulation strategy to enhance the rate and extent of absorption of poorly soluble drugs.

Hypromellose acetate succinate based amorphous solid dispersions via hot melt extrusion: Effect of drug physicochemical properties

In this study, the impact of drug and hydroxypropyl methylcellulose acetate succinate (HPMCAS) grades physicochemical properties on extrusion process, dissolution and stability of the hot melt extruded amorphous solid dispersions (ASDs) of nifedipine and efavirenz was investigated. Incorporation of drugs affected the extrusion temperature required for solid dispersion preparation. Differential scanning calorimetry and powder X-ray diffraction studies confirmed the amorphous conversion of the drugs in the prepared formulations. The amorphous nature of ASDs was unchanged after 3 months of stability testing at 40 °C and 75% relative humidity. The dissolution efficiency of the ASDs was dependent on the log P of the drug. The inhibitory effect of HPMCAS on drug precipitation was dependent on the hydrophobic interactions between drug and polymer, polymer grade, and dose of the drug. The dissolution efficiency and dissolution rate of the ASDs were dependent on the log P of the drug and solubility and hydrophilicity of the polymer grade respectively. The inhibitory effect of HPMCAS on drug precipitation was dependent on the hydrophobic interactions between drug and polymer, polymer grade, and the dissolution dose of the drug.

Role of wetting agents and disintegrants in development of danazol nanocrystalline tablets

Poor wetting and/or particle aggregation are the shortcomings of the dried nanocrystalline suspensions, which subsequently might hinder the superior dissolution performance of the nano-crystalline suspensions. The objective of this study was to evaluate the effect of wetting agents and disintegrants on the dissolution performance of dried nanocrystals of an active pharmaceutical ingredient (API) with poor wetting property. Danazol, a BCS Class II compound with high LogP and low polar surface area, was chosen as a model compound for this study. Danazol nanocrystalline suspension was prepared by wet-media milling and converted into powder via spray granulation either with mannitol or microcrystalline cellulose as carriers at a drug: carrier ratio of 1:9 w/w. Danazol nanocrystalline suspension showed a superior dissolution performance compared to an un-milled danazol suspension. Dried danazol nanocrystals suffered from poor wetting leading to hindered dissolution performance i.e. ~ 40% and ~ 15% drug dissolution within 15 min for the mannitol and microcrystalline cellulose-based granules, respectively. Addition of a lipophilic surfactant (i.e. docusate sodium) at a surfactant: drug ratio of 0.015: 1 w/w during granulation helped in retaining the superior drug dissolution rates i.e. more than 80% drug dissolution within 15 min for mannitol-based granules by enhancing the wettability of dried danazol nanocrystals when compared to a hydrophilic surfactant (i.e. poloxamer 188) or disintegrant (i.e. sodium starch glycolate or croscarmellose sodium). The fast-dissolving mannitol-based granules containing danazol nanocrystals and docusate sodium were compressed into a tablet dosage form. The tablets containing danazol nanocrystals with docusate sodium showed a superior dissolution performance compared to a tablet containing un-milled danazol with docusate sodium.

Long-term Stabilization of Aqueous Doxycycline Formulations, in Mucoadhesive Hydrogels for Treatment of Oral Mucosal Conditions

BACKGROUND

The main aim of this work was to develop stable (>2 years) doxycycline formulation, at clinically relevant concentrations and using clinically relevant formulation. Doxycycline has a MMP- inhibitory effects that is important for the treatment of various oral mucosal conditions. Therefore, protecting doxycycline from degradation in aqueous formulation requires halting or prevention of oxidation and epimerisation of the active compound.

METHODS

Stabilizing excipients were intuitively put together to enhance the stability as a cumulative effort. A total of 30 hydrogels were compared with different types and concentrations of stability enhancing excipients, pH, storage temperatures (4, 25 and 40°C) and mucoadhesive polymers. The duration of the study was from day 1 and up to 58 months. The gelation temperature was adjusted below the actual body temperature. The complexation efficiency between the doxycycline and HPβCD was studied using the DSC, FTIR and XRPD.

RESULTS

The majority of formulations at 4°C were highly stable by the end of 58 months and their stabilities were improved at all 3 temperatures.

CONCLUSION

In conclusion, it is possible to prevent doxycycline from both oxidation and epimerization in an aqueous formulation, for up to 5 years.

Dissolution Enhancement of Atorvastatin Calcium by Cocrystallization

Purpose: To enhance the dissolution rate of the poorly soluble drug atorvastatin calcium (ATC) by cocrystallization with selected coformers. Enhancement of the dissolution rate and solubility of the drug, which is classified as Class II of the Biopharmaceutical Classification System (BCS), is expected to enhance the bioavailability.

Methods: Two methods were used for preparing the cocrystals, solvent drop grinding (SDG) and solvent evaporation (SE) method using 1:1, 1:3, and 1:10 drug-coformer molar ratios. Glucosamine hydrochloride (GluN) and nicotinamide (NIC) were investigated as coformers. The cocrystals, their physical mixtures, and the raw ATC were characterized by fourier transform infrared (FTIR spectroscopy), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), mass spectroscopy (MS), scanning electron microscopy (SEM), solubility, and dissolution rate studies.

Results: SDG and SE were effective in improving the dissolution rate of ATC with both coformers. Drug: coformer ratio 1:3 was optimum. The solubility values for ATC, GluN-, and NIC-cocrystals were 26, to 35 and 50 µg/mL, respectively. The dissolution rate of ATC from cocrystals was > 90% after 5 minutes, compared to 41% untreated ATC.

Conclusion: Cocrystallization significantly improved the solubility and dissolution, in comparison to the untreated ATC.

Interactions Between Paracetamol and Hypromellose in the Solid State

Hydroxypropyl methylcellulose (hypromellose) is a widely known excipient commonly used in the preparation of drug formulations. It can interact with some active pharmaceutical ingredients (APIs), thereby contributing to a reduction in crystallinity, serve as a solvent for API or form stable dispersion with no tendency to aggregation. The aim of the present study was to investigate the effect of hypromellose on the solubility, miscibility and amorphization of paracetamol in mixture with this polymer. Homogenized mixtures of paracetamol with hypromellose were studied using differential scanning calorimetry (DSC), hot-stage microscopy (HSM), Fourier transform infrared (FT-IR) and Raman methods to obtain a deeper insight into the interactions between ingredients in solid state including phase diagram construction for crystalline API and amorphous polymer. A DSC study revealed potential interaction between ingredients resulting in reduced paracetamol crystallinity. This was proved using heating-cooling-heating test to confirm paracetamol amorphization. FT-IR and Raman investigations excluded chemical reaction and hydrogen bonding between ingredients. The phase diagram developed facilitates predictions on the solubility of API in polymer, on the mutual miscibility of ingredients and on the temperature of mixture glass transition.

Immediate-Release Nifedipine Binary Dry Powder Mixtures with Nanocellulose Featuring Enhanced Solubility and Dissolution Rate

Nifedipine (NIF) is a 1,4-dihydropyridine-based calcium channel blocker with poor solubility, whose bioavailability is highly dependent on the type of formulation. Dry powder mixtures of 20% w/w NIF with microcrystalline cellulose (MCC) and its high surface area nanocellulose analogue, which is namely Cladophora (CLAD) cellulose, were produced by heating at the melting temperature of the drug for 1 h. Non-heated samples were used as a reference. The solid-state properties of the mixtures were characterized by scanning electron microscopy, differential scanning calorimetry and X-ray diffraction. The drug release was studied in biorelevant media, including simulated gastric fluid (SGF), fasted-state simulated intestinal fluid (FaSIF) and fed-state simulated intestinal fluid (FeSIF). An enhanced apparent solubility and faster dissolution rate of NIF were observed in the heated mixture of NIF with CLAD-H in all tested biorelevant media (i.e., SGF, FaSIF and FeSIF), which was due to NIF amorphization in the high surface area nanocellulose powder. Ordinary MCC, which is essentially non-porous, did not produce an enhancement of a similar magnitude. The results of the study suggest that dry powder formulation using high surface area nanocellulose is a facile new strategy for formulating calcium channel blocker drugs, which could potentially be a viable alternative to currently used soft gel liquid capsules.

Physical properties and solubility studies of Nifedipine-PEG 1450/HPMCAS-HF solid dispersions

Low-order high-energy nifedipine (NIF) solid dispersions (SDs) were generated by melt solvent amorphization with polyethylene glycol (PEG) 1450 and hypromellose acetate succinate (HPMCAS-HF) to increase NIF solubility while achieving acceptable physical stability. HPMCAS-HF was used as a crystallization inhibitor. Individual formulation components, their physical mixtures (PMs), and SDs were characterized by differential scanning calorimetry, powder X-ray diffraction, and Fourier transform infrared spectroscopy (FTIR). NIF solubility and percent crystallinity (PC) were determined at the initial time and after 5 days stored at 25 °C and 60% RH. FTIR indicated that hydrogen bonding was involved with the amorphization process. FTIR showed that NIF:HPMCAS-HF intermolecular interactions were weaker than NIF:PEG 1450 interactions. NIF:PEG 1450 SD solubilities were significantly higher than their PM counterparts (p < 0.0001). The solubilities of NIF:PEG 1450:HPMCAS-HF SDs were significantly higher than their corresponding NIF:PEG 1450 SDs (p < 0.0001-0.043). All the SD solubilities showed a statistically significant decrease (p < 0.0001) after storage for 5 days. SDs PC were statistically lower than their comparable PMs (p < 0.0001). The PCs of SDs with HPMCAS-HF were significantly lower than SDs not containing only PEG 1450. All SDs exhibited a significant increase in PC (p < 0.0001-0.0089) on storage. Thermogravimetric analysis results showed that HPMCAS-HF bound water at higher temperatures than PEG 1450 (p < 0.0001-0.0039). HPMCAS-HF slowed the crystallization process of SDs, although it did not completely inhibit NIF crystal growth.

Raloxifene-/raloxifene-poly(ethylene glycol) conjugate-loaded microspheres: A novel strategy for drug delivery to bone forming cells

Raloxifene (Ral)- or Ral-poly(ethylene glycol) (PEG) conjugate-loaded microspheres were prepared with poly(ε-caprolactone) (PCL) alone or with the blend of PCL and poly(D,L-lactide-co-glycolide) (PLGA) to provide controlled and sustained Ral release systems. Benefits of these formulations were evaluated on bone regeneration. Ral-loaded PCL microspheres had the highest encapsulation efficiency (70.7±5.0%) among all groups owing to high hydrophobic natures of both Ral and PCL. Cumulative amount of Ral released from Ral-PEG (1:2) conjugate-loaded PCL:PLGA (1:1) microspheres (26.9±8.8%) after 60days was significantly higher relative to other microsphere groups. This finding can be ascribed to two factors: i) Ral-PEG conjugation, resulting in increased water-solubility of Ral and increased degradation rates of PCL and PLGA with enhanced water penetration into the polymer matrix, and ii) usage of PLGA besides PCL in the carrier composition to benefit from less hydrophobic and faster degradable nature of PLGA in comparison to PCL. In vitro cytotoxicity studies performed using adipose-derived mesenchymal stem cells (ASCs) demonstrated that all microspheres were non-toxic. Evaluation of intensities of Alizarin red S staining conducted after 7 and 14days of incubation of ASCs in the release media of the different microsphere groups was performed with Image J analysis software. At day 7, it was observed that the matrix deposited by the cells cultivated in the release medium of Ral-PEG (1:2) conjugate-loaded PCL:PLGA (1:1) microspheres had significantly higher mineral content (26.78±6.23%) than that of the matrix deposited by the cells cultivated in the release media of the other microsphere groups except Ral-loaded PCL:PLGA (1:1) microsphere group. At day 14, Ral release from Ral-PEG (1:2) conjugate-loaded PCL:PLGA (1:1) microsphere group resulted with significantly higher mineralization of the matrix (32.31±1.85%) deposited by ASCs in comparison to all other microsphere groups. Alizarin red S staining results eventuated in parallel with the release results. Thus, it can be suggested that Ral-PEG (1:2) conjugate-loaded PCL:PLGA (1:1) microsphere formulation has a potential as an effective controlled drug delivery system for bone regeneration.

Towards improved solubility of poorly water-soluble drugs: cryogenic co-grinding of piroxicam with carrier polymers

Amorphous solid dispersions (SDs) open up exciting opportunities in formulating poorly water-soluble active pharmaceutical ingredients (APIs). In the present study, novel catalytic pretreated softwood cellulose (CPSC) and polyvinylpyrrolidone (PVP) were investigated as carrier polymers for preparing and stabilizing cryogenic co-ground SDs of poorly water-soluble piroxicam (PRX). CPSC was isolated from pine wood (Pinus sylvestris). Raman and Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) were used for characterizing the solid-state changes and drug-polymer interactions. High-resolution scanning electron microscope (SEM) was used to analyze the particle size and surface morphology of starting materials and final cryogenic co-ground SDs. In addition, the molecular aspects of drug-polymer interactions and stabilization mechanisms are presented. The results showed that the carrier polymer influenced both the degree of amorphization of PRX and stabilization against crystallization. The cryogenic co-ground SDs prepared from PVP showed an enhanced dissolution rate of PRX, while the corresponding SDs prepared from CPSC exhibited a clear sustained release behavior. In conclusion, cryogenic co-grinding provides a versatile method for preparing amorphous SDs of poorly water-soluble APIs. The solid-state stability and dissolution behavior of such co-ground SDs are to a great extent dependent on the carrier polymer used.

Evaluation of drug-polymer solubility curves through formal statistical analysis: comparison of preparation techniques

In this study, the influence of the preparation technique (ball milling, spray drying, and film casting) of a supersaturated amorphous dispersion on the quality of solubility determinations of indomethacin in polyvinylpyrrolidone was investigated by means of statistical analysis. After annealing of the amorphous dispersions above the crystallization temperature for 2 h, the solubility curve was derived from the glass transition temperature of the demixed material using the Gordon-Taylor relationship and fitting with the Flory-Huggins model. The study showed that the predicted solubility from the ball-milled mixtures was not consistent with those from spray drying and film casting, indicating fundamental differences between the preparation techniques. Through formal statistical analysis, the best combination of fit to the Flory-Huggins model and reproducibility of the measurements was analyzed. Ball milling provided the best reproducibility of the three preparation techniques; however, an analysis of residuals revealed a systematic error. In contrast, film casting demonstrated a good fit to the model but poor reproducibility of the measurements. Therefore, this study recommends that techniques such as spray drying or potentially film casting (if experimental reproducibility can be improved) should be used to prepare the amorphous dispersions when performing solubility measurements of this kind.

Cyclodextrin and phospholipid complexation in solubility and dissolution enhancement: a critical and meta-analysis

INTRODUCTION

Poor solubility and dissolution of drugs are the major challenges in drug formulation and delivery. In order to improve the solubility and dissolution profile of drugs, various methods have been investigated so far. The cyclodextrin (CD) complexation and phospholipid (PL) complexation are among the exhaustively investigated methods employed for more precise improvement of the solubility and dissolution of poorly water-soluble drugs.

AREAS COVERED

The article discusses the CD and PL complexation techniques of solubility and dissolution enhancement. Various studies reporting the CD and PL complexation as the potential approaches to improve the dissolution, absorption and the bioavailability of the drugs have been discussed. The article critically reviews the physicochemical properties of CDs and PLs, eligibility of drugs for both the complexation, thermodynamics of complexation, methods of preparation, characterization, advantages, limitation and the meta-analysis of some studies for both the techniques.

EXPERT OPINION

The CD and PL complexation techniques are very useful in improving solubility and dissolution (and hence the bioavailability) of biopharmaceutical classification system Class II and Class IV drugs. The selection of a particular kind of complexation can be made on the basis of eligibility criteria (of drugs) for the individual techniques, cost, stability and effectiveness of the complexes.

Formulation and evaluation of sustained release enteric-coated pellets of budesonide for intestinal delivery

Introduction:

The aim of present work was to develop intestinal-targeted pellets of Budesonide, a potent glucocorticoid, used for the treatment of ulcerative colitis and Crohn's disease by extrusion and spheronization method. Current available oral formulations of Budesonide have low efficacy because of the premature drug release in the upper part of the gastrointestinal tract. In this study, a pH-controlled intestinal-targeted pellet of budesonide was established using 3² full factorial design by giving an enteric coating with Eudragit S100.

Materials and Methods:

Budesonide-sustained release pellets were prepared by extruder and spheronization technique using a combination of water-soluble and permeable polymers by applying 3² full factorial design. The pellets were coated by spray coating technique using Eudragit S100 as an enteric polymer. The pellets were characterized for its flowability, sphericity, friability, and in vitro drug release. Release behaviour was studied in different pH media. The release profile was studied for the mechanism of drug release.

Result:

The optimized formulation showed negligible drug release in the stomach followed by release for 12 h in the intestinal pH. Differential scanning calorimetry and Fourier Transform Infrared Spectroscopy studies indicated no interaction between drug and polymer. Scanning Electron Microscopy image of coated pellets suggested a uniform and smooth coat over the surface of pellets. Accelerated stability studies showed a stable nature of drug in the formulation. All evaluation parameter showed that pellets were good in spherocity and flowability.

Conclusion:

Sustained release pellets of Budesonide could be prepared by extrusion and spheronization which released the drug in intestinal pH for an intestine to treat inflammatory bowel disease. A ratio of polymer combination could be decided using a full factorial design.

Sustained-release pellets of nifedipine using microcrystals combined with MCC-based matrix

The purpose of this study was to prepare sustained-release pellets of nifedipine (NSPs) based on MCC matrix. Wet-milling and extrusion-spheronization techniques were employed to prepare the microcrystals and pellets, respectively. The drug release mechanism and the influencing factors were investigated. After milled with HPMC (E5), the mean particle size of nifedipine in co-grinding mixture (CGM) was 5 μm, which is 15-fold smaller than that of raw material. DSC, X-ray powder diffraction and microscopic observation confirmed the microcrystals of drug were maintained in the CGM. With increased milling time and the content of HPMC, the dissolution rate was greatly enhanced compared with the raw material. The NSPs prepared by MCC and the CGM, which was obtained by cogrinding nifedipine with 5% HPMC solution for 210 min, exhibited sustained release pattern within 8 h. Nifedipine release from MCC-based NSPs followed the Korsmeyer model and closely related to the microstructure of pellet. High stability of NSPs was confirmed after 6 months of accelerated stability test. Using commercially available sustained product as reference, bioequivalence study in beagle dogs was executed and two formulations were bioequivalent. This sustained release pellet formulation of nifedipine was advantageous with convenient and easy scaled-up preparation process.

Dissolution Rate Enhancement, Design and Development of Buccal Drug Delivery of Darifenacin Hydroxypropyl β-Cyclodextrin Inclusion Complexes

Darifenacin is a urinary antispasmodic. The oral absorption of darifenacin is poor due to its low solubility and poor bioavailability (15–19%). Darifenacin was complexed with hydroxylropyl beta-cyclodextrin (Hpβ-CD). The best results were obtained with the coevaporation that interacts in a 1 : 1 drug : cyclodextrin molar ratio. The solid inclusion complexes were found to be amorphous in the characterization. The dissolution rate of darifenacin from the Hpβ-CD solid inclusion complex was increased compared to the powdered drug. The controlled release buccoadhesive patches for the delivery of darifenacin were prepared using HPMC K100M CR and HPMC K15. The coevaporation complex of the drug was used in the formulation due to its increased saturation solubility and increased ease of dissolution. The patches were evaluated for their surface pH, folding endurance, swelling, mucoadhesive properties, in vitro residence time, vapour transmission test, and in vitro and ex vivo release studies. Formulations Hb2 (2%) and Pb4 (4%) were found to be optimized. These two formulations can be used for buccal delivery of darifenacin which avoids first pass effect and leads to increased bioavailability of darifenacin.

Solubility enhancement, physicochemical characterization and formulation of fast-dissolving tablet of nifedipine-betacyclodextrin complexes

The main objective of the study was to enhance the dissolution of nifedipine, a poorly water soluble drug by betacyclodextrin complexation and to study the effect of the preparation method on the in vitro dissolution profile. The stoichiometric ratio determined by phase solubility analysis for inclusion complexation of nifedipine with β-cyclodextrin was 1:1. Binary complex was prepared by different methods and was further characterized using XRD, DSC and FT-IR. A saturation solubility study was carried out to evaluate the increase in solubility of nifedipine. The optimized complex was formulated into fast-dissolving tablets by using the superdisintegrants Doshion P544, pregelatinized starch, crospovidone, sodium starch glycolate and croscarmellose sodium by direct compression. Tablets were evaluated for friability, hardness, weight variation, disintegration and in vitro dissolution. Tablets showed an enhanced dissolution rate compared to pure nifedipine.

Effect of drug-carrier interaction on the dissolution behavior of solid dispersion tablets

The objective of this study was to compare the dissolution behavior of tablets prepared from solid dispersions with and without drug-carrier interactions. Diazepam and nifedipine were used as model drugs. Two types of carriers were used; polyvinylpyrrolidone (PVP K12, K30 and K60) and saccharides (inulin 1.8 kDa, 4 kDa and 6.5 kDa). Solid dispersions with various drug loads were prepared by lyophilization. It was found that the drug solubility in aqueous PVP solutions was significantly increased indicating the presence of drug-carrier interaction while the drug solubility was not affected by the saccharides indicating absence of drug-carrier interaction. X-ray powder diffraction and modulated differential scanning calorimetry revealed that all solid dispersions were fully amorphous. Dissolution behavior of solid dispersion tablets based on either the PVPs or saccharides was governed by both dissolution of the carrier and drug load. It was shown that a fast drug dissolution of solid dispersions with a high drug load could be obtained with carrier that showed interaction with the drug.

Enhanced dissolution and bioavailability of raloxifene hydrochloride by co-grinding with different superdisintegrants

The present study investigated the effect of co-grinding raloxifene HCL (RHCL) with different superdisintegrants, namely crospovidone (CP), croscarmellose sodium (CCS) and sodium starch glycolate (SSG), using a ball mill, in order to determine the potential effect on dissolution rate and bioavailability of raloxifene hydrochloride (RHCL). The dissolution studies of the co-ground compositions and the corresponding physical mixtures were carried out in U.S. Pharmacopeia (USP) Type II apparatus. The solid state interactions of the co-ground and the physical mixtures were evaluated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The pharmacokinetics of co-ground mixture (1 : 5 RHCL : CP) and milled RHCL was evaluated following oral administration (25 mg/kg) in healthy female Sprague-Dawley rats. DSC studies showed that the crystalline nature of RHCL was reduced after co-grinding with superdisintegrants, while co-grinding with CP resulted in significant particle-size reduction of the mixture. Significant enhancement in dissolution rate was observed with co-ground mixture of RHCL with CP (1 : 5). The extent of the mean plasma exposures of RHCL was 7-fold higher in animals treated with co-ground mixture of RHCL, CP (1 : 5) compared to animals treated with milled RHCL. Co-grinding of RHCL with CP, reduced drug crystallinity, increased the rate and extent of dissolution, and improved bioavailability.

Solid state interaction of raloxifene HCl with different hydrophilic carriers during co-grinding and its effect on dissolution rate

This study investigated the effects of different classes of hydrophilic carriers (poly vinyl pyrrolidones [PVPs] [Plasdone K-25 and Plasdone S-630], cellulosic polymers [hydroxypropyl methyl cellulose and hydroxy propyl cellulose], and Sodium Alginate) on the solid state and dissolution rate of Raloxifene hydrochloride (R-HCl). Solid state characterizations of co-ground mixtures and physical mixtures in 1:1 and 1:2 ratios of drug to polymer were performed by employing laser diffractometer for particle size and differential scanning calorimetry (DSC) for solid state interactions. The results of particle size studies showed that only co-grinding with PVPs was more effective in the reduction of particle size than the milling of drug alone. DSC study indicated that the crystalline nature of the drug was reduced after co-grinding with PVPs when compared with their corresponding physical mixtures. The hydrophilic carriers other than PVPs did not reduce the crystalline nature of the drug significantly. X-ray diffraction and scanning electron microscopy were carried out for selected batches to confirm DSC results. Significant enhancement in dissolution rate and extent was observed with co-ground mixtures of drug and PVPs. Plasdone S-630 was found to be a better carrier for R-HCl in terms of achieving improvement in dissolution. In vitro dissolution data can be described by Hixson-Crowell model, indicating the drug release mechanism predominated by erosion.

Preparation and characterization of co-grinded mixtures of aceclofenac and neusilin US2 for dissolution enhancement of aceclofenac

The present study was carried out with a view to enhance the dissolution of poorly water-soluble BCS-class II drug aceclofenac by co-grinding with novel porous carrier Neusilin US(2.) (amorphous microporous granules of magnesium aluminosilicate, Fuji Chemical Industry, Toyama, Japan). Neusilin US(2) has been used as an important pharmaceutical excipient for solubility enhancement. Co-grinding of aceclofenac with Neusilin US(2) in a ratio of 1:5 was carried out by ball milling for 20 h. Samples of co-ground mixtures were withdrawn at the end of every 5 h. and characterized for X-ray powder diffraction, differential scanning calorimetry, and Fourier-transform infrared spectroscopy. The analysis revealed the conversion of crystalline aceclofenac to its amorphous form upon milling with Neusilin US(2). Further, in vitro dissolution rate of aceclofenac from co-ground mixture was significantly higher compared to pure aceclofenac. The accelerated stability study of co-ground mixture was carried out at 40 degrees C/75%RH for 4 weeks, and it showed that there was no reversion from amorphous to crystalline form. Thus, it is advantageous to use a porous carrier like Neusilin US(2) in improvement of dissolution of poorly soluble drugs.

Nifedipine nanoparticle agglomeration as a dry powder aerosol formulation strategy

Efficient administration of drugs represents a leading challenge in pulmonary medicine. Dry powder aerosols are of great interest compared to traditional aerosolized liquid formulations in that they may offer improved stability, ease of administration, and simple device design. Particles 1-5microm in size typically facilitate lung deposition. Nanoparticles may be exhaled as a result of their small size; however, they are desired to enhance the dissolution rate of poorly soluble drugs. Nanoparticles of the hypertension drug nifedipine were co-precipitated with stearic acid to form a colloid exhibiting negative surface charge. Nifedipine nanoparticle colloids were destabilized by using sodium chloride to disrupt the electrostatic repulsion between particles as a means to achieve the agglomerated nanoparticles of a controlled size. The aerodynamic performance of agglomerated nanoparticles was determined by cascade impaction. The powders were found to be well suited for pulmonary delivery. In addition, nanoparticle agglomerates revealed enhanced dissolution of the drug species suggesting the value of this formulation approach for poorly water-soluble pulmonary medicines. Ultimately, nifedipine powders are envisioned as an approach to treat pulmonary hypertension.

Kinetic Analysis of Chlorpropamide Dissolution from Solid Dispersions

Solid dispersions (SDs) of chlorpropamide were prepared by the solvent deposition technique using two grades of microcrystalline cellulose as carrier materials with different ratios of drug to carrier. The dissolution rate of chlorpropmide from the SDs was carried out at two physiological pH values of 1.1 and 7.25 simulating gastric and intestinal environments. The dissolution was dependent on the grade, the ratio of drug to carrier and pH. The higher dissolution was observed for more hydrophilic grade of the carrier as well as the higher ratio of carrier to drug. At the higher pH the drug dissolved much faster than the lower pH. X-ray diffraction showed some reduced drug crystallinity in SDs whereas infrared spectroscopy revealed no drug interactions with solvent and the carriers. The enhanced dissolution was attributed to the reduced drug crystallinity, decreased particle size, increased wettability and reduced aggregation of the hydrophobic drug particles. A novel model denoted as reciprocal powered time model with its theoretical justification was employed to analyze the dissolution data and proved to be superior to commonly used models for the analysis of the data. There was a quantitative relation between the model parameter and the ratio of carrier to drug which could be of value in dissolution rate prediction.

Studies on biodegradable polymeric nanoparticles of risperidone: in vitro and in vivo evaluation

AIM

The aim of this work was to develop extended-release risperidone nanoparticles for parenteral delivery (intravenous) and to reduce the dose-dependent extrapyramidal side effects of risperidone.

METHODS

Polymeric nanoparticles containing risperidone made of poly (epsilon-caprolactone) were designed by the nanoprecipitation method using polymeric stabilizers (poloxamers). The in vivo efficacy of prepared formulations and the risperidone solution was studied by administering them intravenously to apomorphine-treated mice. Extrapyramidal side effects of the risperidone and its formulations were also studied.

RESULTS

The particle size of the prepared nanoparticles ranged between 99 and 304 nm. Approximately 78-85% drug-encapsulation efficiency was achieved when risperidone was loaded at 1.7-4.1% by weight of the polymer. During in vivo studies, prepared risperidone-containing formulations showed a significant prolonged antipsychotic effect than that of risperidone solution, also having less extrapyramidal side effects.

CONCLUSION

The prolonged effect of risperidone was obtained from the nanoparticles of risperidone administered by the intravenous route and this may improve the treatment of psychotic disorders by dose reduction.

Preparation of glass solutions of three poorly water soluble drugs by spray drying, melt extrusion and ball milling

The aim of this study was to investigate the influence of the manufacturing process on the physicochemical properties of three poorly water soluble compounds (carbamazepine, dipyridamole, and indomethacin) when processed with a polymer (polyvinylpyrrolidone K30 (PVP)) at a 1:2 drug to polymer ratio. Melt extrusion, spray drying, and ball milling techniques were used to prepare glass solutions. Product homogeneity, dissolution, physical stability, and drug/polymer interactions were investigated. Particular attention was paid to solid phase analysis using XRPD, modulated temperature DSC, optical microscopy, and Raman microscopy and the importance of using a combination of techniques was demonstrated. The latter technique when applied to freshly ball milled samples exhibited the presence of drug and polymer rich areas, indicating that complete glass solution formation had not occurred. The three compounds produced products with differing physical stability with indomethacin proving the most physically stable. These differences in physical stability were attributed to hydrogen bonding of drug and polymer. The manufacturing technique did not influence physical stability, but it did affect dissolution. The dissolution of the spray-dried material was generally poor, compared to melt extruded and ball milled products. This was probably due to rapid dissolution of PVP from the small particles of the spray-dried products.

Preparation of Drug Nanoparticles by Co-grinding with Cyclodextrin: Formation Mechanism and Factors Affecting Nanoparticle Formation

The aim of this study was to investigate the factors affecting the formation of pranlukast nanoparticle prepared by co-grinding with beta-cyclodextrin (beta-CD) and to elucidate the mechanism of nanoparticle formation. The effects of grinding time, moisture content and CD content on the nanoparticle formation were evaluated by means of UV quantitative determination and particle size analysis. High-resolution scanning electron microscopy (HRSEM) was employed to observe drug nanoparticles in the ground mixture. Nanoparticle recovery was higher than 95% for 2 : 1 molecular mixtures of beta-CD : pranlukast which had been ground for 10 min with moisture levels between 10 and 15%. While that of the 1 : 2 ground mixture prepared at 8% moisture level was only 57%. Nanoparticle recovery from beta-CD : pranlukast 2 : 1 mixture ground for 1 min was 2.5%, while that of the 10 min ground mixture was as high as 95%. HRSEM demonstrated that primary drug nanoparticles having a particle size around 50 nm were observed in the ground mixture. The grinding time, the moisture content, and the CD content had significant influences on the formation of drug nanoparticles. The CD matrix may form and stabilize primary particles by its interaction with the particle surface through water molecules. Primary nanoparticles existed in the ground mixture as 50 nm drug nanocrystallites.