International Journal of Pharmaceutics (v.259, #1-2)

Coagulation factor VIII: structure and stability by Wei Wang; Y.John Wang; Drew N Kelner (1-15).
Factor VIII (FVIII), a coagulation factor in the blood, is one of the most complex proteins known today. To facilitate the rapid development of a more convenient and safer FVIII product and to improve the quality of life for hemophilia patients, this short article reviews the recent investigations on the structure, activity, and more importantly, stability of FVIII.
Keywords: FVIII; Structure; Stability; Formulation; Aggregation; Oxidation;

Evaluation of different calorimetric methods to determine the glass transition temperature and molecular mobility below T g for amorphous drugs by I. Weuts; D. Kempen; K. Six; J. Peeters; G. Verreck; M. Brewster; G. Van den Mooter (17-25).
The purpose of the present study was to compare different calorimetric methods used to determine the glass transition temperature (T g) and to evaluate the relaxation behaviour and hence the stability of amorphous drugs below their T g. Data showed that the values of the activation energy for the transition of a glass to its super-cooled liquid state qualitatively correlate with the values of the mean molecular relaxation time constant of ketoconazole, itraconazole and miconazole, three structurally related drugs. Estimation of the molecular mobility by activation energy calculation indicated that loperamide was more stable than its two building blocks T263 and R731. It was further shown that the most commonly used approach to determine T g (T g  1/2c p ) leads to erroneous values when enthalpy recovery is significant. In this case, an alternative method based on enthalpic considerations leads to results in accordance to basic thermodynamics. Estimation of molecular mobility based on activation energy calculations is therefore considered to be a valuable alternative for the method based on measurement of the extent of relaxation. When enthalpy relaxation is important, the use of T g  1/2c p leads to an overestimation of the T g.
Keywords: Differential scanning calorimetry; Molecular mobility; Amorphous drugs; Azole derivates; Loperamide;

The purpose of this study is to characterize the monoclinic crystals in tablets by using X-ray powder diffraction data and to evaluate the deformation feature of crystals during compression. The monoclinic crystals of acetaminophen and benzoic acid were used as the samples. The observed X-ray diffraction intensities were fitted to the analytic expression, and the fitting parameters, such as the lattice parameters, the peak-width parameters, the preferred orientation parameter and peak asymmetric parameter were optimized by a non-linear least-squares procedure. The Gauss and March distribution functions were used to correct the preferred orientation of crystallites in the tablet. The March function performed better in correcting the modification of diffraction intensity by preferred orientation of crystallites, suggesting that the crystallites in the tablets had fiber texture with axial orientation. Although a broadening of diffraction peaks was observed in acetaminophen tablets with an increase of compression pressure, little broadening was observed in the benzoic tablets. These results suggest that “acetaminophen is a material consolidating by fragmentation of crystalline particles and benzoic acid is a material consolidating by plastic deformation then occurred rearrangement of molecules during compression”. A pattern-fitting procedure is the superior method for characterizing the crystalline drugs of monoclinic crystals in the tablets, as well as orthorhombic isoniazid and mannitol crystals reported in the previous paper.
Keywords: X-ray diffraction; Pattern-fitting; Monoclinic crystals; Preferred orientation; Lattice disorder; Tablet;

Convolution method to predict drug concentration profiles of 2,3,5,6-tetramethylpyrazine following transdermal application by Xiaohong Qi; Rong (Ron) Liu; Duxin Sun; Chrisita Ackermann; Huimin Hou (39-45).
The objective of this work is to predict the systemic drug concentration of 2,3,5,6-tetramethylpyrazine (TMP) following transdermal application in rabbits from the in vitro skin permeation data. The in vitro skin permeation was studied in Franz diffusion cells. Pharmacokinetic evaluation of TMP following transdermal application and bolus intravenous administration were carried out in New Zealand White (NZW) rabbits. Drug concentration–time curve following transdermal application was predicted via the convolution procedure using an in vitro skin permeation data as a weighting function, and the intravenous data as an unit impulse response. The results showed that the predicted drug concentration following transdermal application by convolution method was in good agreement with the observed drug absorption profiles. These findings indicated that in vitro skin permeation tests could be useful to predict in vivo drug absorption profiles following transdermal application.
Keywords: In vitro skin permeation; In vivo drug absorption; Transdermal delivery systems; Convolution;

Targeted retentive device for oro-dental infections: formulation and development by A. Ahuja; J. Ali; R. Sarkar; A. Shareef; R.K. Khar (47-55).
Fibers loaded with amoxycillin trihydrate were prepared for oro-dental infections using melt spinning technique. Ethylene vinyl acetate, a biocompatible polymer was used for providing controlled release effect over a period of several days. The fibers were evaluated for in vitro release in alkaline borate buffer pH 8.1 in a biological shaker which was rotated at 50 rpm at 37 °C. In situ studies were carried out in continuous flow through apparatus which simulated the conditions of periodontal pocket. Microbiological evaluation was carried out on strains commonly implicated in oro-dental infections namely S. aureus, S. mutans, and Bacteroides cereus. Results of in vitro release studies revealed that the effect was sustained over a period of 6 days and followed Fickian diffusion mechanism. In situ release study samples were well above the minimum inhibitory concentration of the drug. These samples were effective in inhibiting the growth of the above-mentioned strains. The optimized formulation was characterized for general appearance, content uniformity, and SEM. Stability studies carried out on the formulation showed the degradation rate constant value of 2.79×10−4 per day. Retentive fibers were found to be very effective in controlled delivery of amoxycillin, and hence can be feasible alternative to systemic administration.
Keywords: Retentive fiber; Periodontitis; Amoxycillin trihydrate; In vitro studies; In situ studies;

Development and optimisation of alginate-PMCG-alginate microcapsules for cell immobilisation by G Orive; R.M Hernández; A.R Gascón; M Igartua; J.L Pedraz (57-68).
Mechanical stability, uniformity of size, complete encapsulation of cells and optimal microenvironment are major challenges in the design and development of microcapsules for cell immobilisation purposes. In this work, a novel microcapsule chemistry based on polyelectrolyte complexation between alginate and poly(methylene-co-guanidine) (PMCG) is presented. We have characterised the effect of PMCG concentration and time of exposure on microcapsule diameter and membrane thickness, selecting a PMCG concentration of 0.5% (v/v) and an exposure time of 1 min as optimal parameters for a correct coating. Afterwards, the mechanically most resistant alginate-PMCG-alginate (A-PMCG-A) microcapsule type was chosen according to two different stability studies. Beads with a solid core and an inhomogeneous internal configuration resulted in stronger microcapsules. Further, the selected A-PMCG-A beads presented both an increased stability compared to classical Ca2+/alginate and alginate-poly-l-lysine-alginate (APA) microcapsules, and had an adequate microenvironment for cell viability. This new chemistry allows the controlled adjustment of microcapsule size and wall thickness, offering new alternatives for cell transplantation.
Keywords: Microcapsule; Alginate; Mechanical stability; Cell encapsulation;

One-step dry-coated tablets (OSDRC) were prepared using materials which are generally used in pharmaceutical tablets. The radial tensile strength of OSDRC was measured for various compression pressures and core porosities before the final compression to compare with that of conventional dry-coated tablets (DC). Furthermore, stress relaxation in the compression process was investigated. Radial tensile strength and stress relaxation profiles of OSDRC were the same as those of conventional DC. X-ray computerized tomography (CT) of the tablets showed that the density distribution of both tablets was also the same. Thus, we concluded that OSDRC and conventional DC have the same compression characteristics and physical properties. The OSDRC-system was executed by the use of upper and lower punches, which had a double structure, a center punch, and an outer punch surrounding the center punch. The OSDRC process consists of three compressions to make the lower-outer layer (1st-outer layer), the core, and the whole tablet including the upper-outer and side-outer layers (2nd-outer layer). At first, the powder for the 1st-outer layer fills a space, which is made by the lower-center punch and lower-outer punch, and is pre-compressed by the upper-center punch. Then, while the upper-center punch pushes the pre-compressed 1st-outer layer, the lower-center punch is slid down. The upper-center punch is then pulled away to make a space, which is filled with the powder for the core. This is then pre-compressed by the upper-center punch. Finally, the lower-outer punch is slid downward and the powder for the 2nd-outer layer fills and surrounds the pre-compressed core/1st-outer layer completely. The core/1st-outer layer and the 2nd-outer layer complex is then compressed by the upper and lower punches in which the center punches are unified with the outer punches, respectively. This system can be assembled onto the turn table of a rotary tableting machine, and can make a dry-coated tablet in a single turn.
Keywords: One-step dry-coated tablets; Dry-coated tablets; Compression coated tablets; OSDRC-system; Compression test; Stress relaxation; Tensile strength;

Preparation of poly(dl-lactide-co-glycolide) microspheres encapsulating all-trans retinoic acid by Young-Il Jeong; Jin-Gyu Song; Sam-Suk Kang; Hyang-Hwa Ryu; Young-Hwa Lee; Chan Choi; Boo-Ahn Shin; Kyung-Keun Kim; Kyu-Youn Ahn; Shin Jung (79-91).
Poly(dl-lactide-co-glycolide) (PLGA) microspheres containing all-trans retinoic acid (atRA) were prepared by o/w solvent evaporation method and various preparation parameters, such as poly(vinyl alcohol) (PVA) concentration in aqueous solution, PVA MW, drug weight, solvent, polymer MW, and polymer weight, on the characteristics of microspheres and drug release were investigated. PVA concentration in water phase was a critical factor in making microspheres consistently with smooth surface and round shape. In our study, at least 2% (w/v) of PVA in aqueous solution was necessary for making microspheres with round shape. The particle size of microspheres ranged 10–100 μm. AtRA was slowly released from PLGA microspheres over 30 days. Sterilization of microspheres by ethylene oxide (EO) gas at 37 °C did not significantly affect the characteristics of drug release or its morphology. Cell growth inhibition of atRA was affected by preparation process of microspheres rather than the EO-gas sterilization process. These results indicate that PLGA microspheres containing atRA are acceptable for controlled release devices for use in the treatment of brain tumor.
Keywords: All-trans retinoic acid; Poly(dl-lactide-co-glycolide); Controlled release; Biodegradable microspheres; Brain tumor;

Nanoparticles bearing polyethyleneglycol-coupled transferrin as gene carriers: preparation and in vitro evaluation by Yaping Li; Manfred Ogris; Ernst Wagner; Jaroslav Pelisek; Martina Rüffer (93-101).
The aims of this work were to determine the stability of pDNA against various conditions during microencapsulation, prepare transferrin (TF)-conjugated PEGylated polycyanoacrylate nanoparticles (TF–PEG-nanoparticles), and assess its physicochemical characteristics and in vitro targeting cells association. The open circular forms of pDNA obviously increased when pDNA was emulsified into organic solution under sonification. When pDNA solution (pH 7.0) contained 1, 3 or 5% (w/v) PVA, after sonification, average 48.2, 59.4 and 62.1% of double-supercoiled DNA (dsDNA) were preserved, respectively. When medium of pDNA was 0.9% NaCl (pH 7.0), 0.1 M NaHCO3 (pH 8.0) or phosphate buffer (pH 8.0), average 53.1, 69.3 and 56.9% of dsDNA remained after sonification, respectively. Poly(aminopoly(ethylene glycol)cyanoacrylate-co-hexadecyl cyanoacrylate) (poly(H2NPEGCA-co-HDCA)) showed a slight influence on pDNA in 0.1 M NaHCO3 (pH 8.0) when its concentration increased from 0.5 to 4% (w/v). TF–PEG-nanoparticles loading pDNA were spherical in shape with size under 200 nm and entrapment efficiency 35–50%. 0.1 M NaHCO3 with 3% PVA (w/v) could largely reduce the damage of pDNA during microencapsulation. TF–PEG-nanoparticles bore 1–3% of the total PEG chains conjugated to TF molecules, and exhibited the burst effect with over 30% drug release within 1 day. After the first phase, pDNA release profiles displayed a sustained release. The amount of cumulated pDNA release over 7 days was: 86.3, 81.5 and 74.4% for 1, 2 and 4% polymer nanoparticles, respectively. The degree of target K562 cell binding of TF–PEG-nanoparticles was greater than that of non-targeted PEG-nanoparticles at 4 °C. The presence of free TF decreased significantly the degree of cell binding of TF–PEG-nanoparticles, which revealed that the binding of TF–PEG-nanoparticles to K562 cells was indeed receptor specific. These results suggested that TF–PEG-nanoparticles were useful for delivery of pDNA to target cells.
Keywords: pDNA; Nanoparticles; Transferrin; Polyethylene glycol; Poly(cyanoacrylate);

Preparation of sustained-release nitrendipine microspheres with Eudragit RS and Aerosil using quasi-emulsion solvent diffusion method by Ming-shi Yang; Fu-de Cui; Ben-gang You; Yu-ling Fan; Liang Wang; Peng Yue; He Yang (103-113).
Sustained-release nitrendipine microspheres were prepared in liquid system by quasi-emulsion solvent diffusion method, in which the Aerosil was employed as an inert dispersing carrier to improve the dissolution rate of nitrendipine, and Eudragit RS as a retarding agent to control the release rate. The resultant microspheres were evaluated for the recovery, bulk density, average particle size, drug loading, and incorporation efficiency. And the factors affecting the formation of microspheres and the drug-release rate were investigated. It was observed by a scanning electron microscope (SEM) that the microspheres were finely spherical and uniform, and no entire nitrendipine crystals were observed visually. The results of X-ray diffraction indicated that nitrendipine in microspheres was disordered, suggesting that nitrendipine was highly dispersed in microspheres. The drug loading of microspheres was enhanced with increasing the ratio of drug to excipients, and the incorporation efficiency was always >90%. The formation of microspheres was mainly influenced by the amount of bridging liquid and sodium dodecyl sulfate (SDS) in poor solvent. The dissolution profiles could be modulated with adjusting the amount of retarding agent and dispersing carrier formulated.
Keywords: Nitrendipine; Sustained-release microsphere; Quasi-emulsion solvent diffusion method; Eudragit RS; Aerosil; Solvent deposition system;

Effect of copolymer composition on the physicochemical characteristics, in vitro stability, and biodistribution of PLGA–mPEG nanoparticles by K. Avgoustakis; A. Beletsi; Z. Panagi; P. Klepetsanis; E. Livaniou; G. Evangelatos; D.S. Ithakissios (115-127).
The physicochemical properties, the colloidal stability in vitro and the biodistribution properties in mice of different PLGA–mPEG nanoparticle compositions were investigated. The nanoparticles were prepared by a precipitation–solvent evaporation technique. The physical characteristics and the colloidal stability of the PLGA–mPEG nanoparticles were significantly influenced by the composition of the PLGA–mPEG copolymer used to prepare the nanoparticles. PLGA–mPEG nanoparticles prepared from copolymers having relatively high mPEG/PLGA ratios were smaller and less stable than those prepared from copolymers having relatively low mPEG/PLGA ratios. All PLGA–mPEG nanoparticle compositions exhibited prolonged residence in blood, compared to the conventional PLGA nanoparticles. The composition of the PLGA–mPEG copolymer affected significantly the blood residence time and the biodistribution of the PLGA–mPEG nanoparticles in liver, spleen and bones. The in vivo behavior of the different PLGA–mPEG nanoparticle compositions did not appear to correlate with their in vitro stability. Optimum mPEG/PLGA ratios appeared to exist leading to long blood circulation times of the PLGA–mPEG nanoparticles. This may be associated with the effects of the mPEG/PLGA ratio on the density of PEG on the surface of the nanoparticles and on the size of the nanoparticles.
Keywords: Poly(lactide-co-glycolide)-(polyethyleneglycol) nanoparticles; Biodistribution; Blood clearance; Copolymer composition; Colloidal stability;

Degradation kinetics of mometasone furoate in aqueous systems by Xiao Wei Teng; David C Cutler; Neal M Davies (129-141).
Mometasone furoate (MF) is a synthetic glucocorticoid. There is little information available on the stability of MF and no degradation products have been unequivocally identified. Thus, the primary objective of this study was to characterize the degradation of MF, qualitatively and quantitatively. Stability of MF decreased with increasing pH (>4) and decreasing ionic strength in aqueous media. The chemical stability of MF in aqueous systems was significantly dependent on pH. MF appeared to be stable at pH<4 but degraded to four products at higher pH. The degradation of MF in aqueous solutions follows pseudo-first-order kinetics and involved a series of parallel and consecutive reactions. The turnover of MF and its products appears to be catalyzed by the hydroxide ion. The pH dependence of these reactions should be considered, when formulating or extemporaneously compounding MF formulations. An optimal pH of stability was below pH 4. The changes in pH, however, do not appear to be the only factor of importance, since an increase in ionic strength and buffer concentration displayed a stabilizing effect on this glucocorticoid in the buffers tested. Trace metal ions are unlikely to be involved in degradation of MF in aqueous solution.
Keywords: Glucocorticoid; Stability; Degradation;

Drug complexation, in vitro release and cellular entry of dendrimers and hyperbranched polymers by Parag Kolhe; Ekta Misra; Rangaramanujam M. Kannan; Sujatha Kannan; Mary Lieh-Lai (143-160).
Highly branched, functionalized polymers have potential to act as efficient drug carrier systems. Dendrimers are ideal candidates among model hyperbranched polymers because of their well-defined structure and high density of functional groups. Using ibuprofen as a model drug, we studied the interaction between the drug and Polyamidoamine (PAMAM) dendrimers (generations 3 and 4 with NH2 functionality) and Perstrop Polyol (generation 5, hyperbranched polyester with OH functionality). FTIR and NMR studies suggest that ibuprofen predominantly forms a complex with PAMAM dendrimers because of the ionic interaction between the NH2 end groups and the carboxyl group of ibuprofen. On an average, up to 78 molecules of ibuprofen could be incorporated into one molecule of PAMAM-G4-NH2 with 64 end groups. This complex is stable in deionized water and methanol. The in vitro release of ibuprofen from drug–dendrimer complex is appreciably slower compared to pure ibuprofen. The complexed drug enters A549 cells much more rapidly than pure drug suggesting that dendrimers may be able to carry the complexed drug inside cells efficiently. Hyperbranched Polyol (with 128 OH end groups) appears to encapsulate approximately 24 drug molecules. Perhaps the lack of strong interactions between the OH end groups and the drugs prevents complex formation.
Keywords: Ibuprofen; PAMAM; Polymer drug complexation; Hyperbranched polymer; Dendrimer;

The preparation of agglomerates containing solid dispersions of diazepam by melt agglomeration in a high shear mixer by Anette Seo; Per Holm; Henning Gjelstrup Kristensen; Torben Schæfer (161-171).
The aim of this study was to prepare by melt agglomeration agglomerates containing solid dispersions of diazepam as poorly water-soluble model drug in order to evaluate the possibility of improving the dissolution rate. Lactose monohydrate was melt agglomerated with polyethylene glycol (PEG) 3000 or Gelucire® 50/13 (mixture of glycerides and PEG esters of fatty acids) as meltable binders in a high shear mixer. The binders were added either as a mixture of melted binder and diazepam by a pump-on procedure or by a melt-in procedure of solid binder particles. Different drug concentrations, maximum manufacturing temperatures, and cooling rates were investigated. It was found to be possible to increase the dissolution rate of diazepam by melt agglomeration. A higher dissolution rate was obtained with a lower drug concentration. Admixing the binders by the melt-in procedure resulted in similar dissolution rates as the pump-on procedure. The different maximum manufacturing temperatures and cooling rates were found to have complex effects on the dissolution rate for formulations containing PEG 3000, whereas only minor effects of the cooling procedure were found with Gelucire 50/13. Gelucire 50/13 resulted in faster dissolution rates compared to PEG 3000.
Keywords: Melt agglomeration; High shear mixer; Polyethylene glycol; Diazepam; Solid dispersion; Dissolution rate;

Effect of hydrophilic polymers on the release of diltiazem hydrochloride from elementary osmotic pumps by D Prabakaran; Paramjit Singh; Parijat Kanaujia; Suresh P Vyas (173-179).
Diltiazem hydrochloride (DLTZ) is a freely water-soluble drug, because of its higher aqueous solubility, the suitability of the drug with elementary osmotic pumps is restricted. Plain DLTZ elementary osmotic pump had shown higher release rate. Drug entrapment in polymer matrix or addition of release retardant materials (various polymers) can reduce the release rate of drug. In present study, effect of appropriate hydrophilic polymers (HP) on the release pattern was investigated. Ingredients of the system were optimized for parameters like drug:polymer ratio and amount of osmogent, for the desired release pattern. Two optimized formulations were selected for further characterization. Theoretical release rate of the formulations were also determined and compared. Different dissolution models were applied to drug release data in order to establish release mechanism and kinetics. Criteria for selecting the most appropriate model were based on best goodness of fit and smallest sum of squared residuals.
Keywords: Osmotic pumps; Hydrophilic polymers; Diltiazem hydrochloride; Release kinetics;

Three new N 1-alkylcarbonyl-5-fluorouracil derivatives that are prodrugs of 5-fluorouracil (FU), one of them being a co-drug FU-retinoic acid (RA), were studied as potentially effective drugs against postsurgical proliferative vitreoretinopathy (PVR). The stability of N 1-octenoylFU (3), N 1-lauroylFU (2), and N 1-retinoylFU (4) in aqueous medium, their solubility in silicone oil (SiO), the kinetics of FU release in an in vitro system were determined. Compound 3 is very rapidly soluble in SiO. Its saturation concentration, reached after 6 h, is 233±13 μg g−1 SiO. Compound 2 is not very soluble in SiO but its kinetic of solubilization is fast. Its saturation concentration, reached after 2 days, is 27±2 μg g−1 SiO. Compound 4 is poorly soluble in SiO. A concentration plateau, with a mean value of 4 μg g−1 SiO, is reached after 4 days. The addition in SiO of 5% of a perfluorinated perhydrogenated alkene greatly improves the solubilization of compound 4. Two different types of FU release are observed. For compound 3, the release is fast and is achieved after 1 day. For compounds 2 and 4, the release is slower and is ended at 10 and 27 days, respectively. The solubility of the prodrugs in SiO is not correlated with their lipophilicity, whereas the release rate of FU decreased with increased lipophilicity of the prodrug. The most promising prodrug is compound 4 that slowly releases two active drugs (FU and RA) with a t 1/2 release of 5.8 days. It might be interesting for the treatment of PVR. However, an in vivo study on an animal model of PVR is necessary to prove the efficacy of this formulation and to study its toxicity.
Keywords: N 1-Alkylcarbonyl-5-fluorouracil prodrugs; N 1-Octenoyl-5-fluorouracil; N 1-Lauroyl-5-fluorouracil; N 1-Retinoyl-5-fluorouracil; Solubility in silicone oil; In vitro release of 5-fluorouracil; Proliferative vitreoretinopathy;

Effect of 1-O-ethyl-3-butylcyclohexanol on the skin permeation of drugs with different physicochemical characteristics by Chao Jie Li; Yasuko Obata; Kimio Higashiyama; Tsuneji Nagai; Kozo Takayama (193-198).
The effects of 1-O-ethyl-3-butylcyclohexanol (OEBC) on the in vitro skin permeation of ten model drugs with different physicochemical properties across excised rat skin were evaluated. The results showed that the addition of OEBC significantly improved the in vitro skin permeation of the model drugs compared with the control (without OEBC). To clarify the promoting mechanism of OEBC, a multiple regression analysis was employed. When the permeation study was performed without OEBC, the permeability coefficient was quantitatively predicted as a linear function of molecular weight (log MW) and their lipophilicity (partition coefficient of drugs between octanol and water (log  K o/w)) with a sufficiently high correlation coefficient (r=0.842). It was suggested that skin permeation of drugs without OEBC was explained as a function of diffusion of drugs through the skin and partitioning of drugs to the skin. Although OEBC was administered, the permeability coefficient of drugs cannot be predicted as a linear function of log MW and log  K o/w (r=0.572).
Keywords: 1-O-ethyl-3-butylcyclohexanol; Absorption enhancer; Skin permeation; Lipophilicity; Molecular weight; Physicochemical properties; Multiple regression analysis;

Corrigendum to “Formulation and stability of surface-tethered DNA–gold–dendron nanoparticles” by Nasir Hussain; Baljit Singh; Thiagarajan Sakthivel; Alexander T. Florence (201).

NOTICEBOARD (203-205).