International Journal of Pharmaceutics (v.281, #1-2)
TITLE PAGE (EDI BOARD) (iii).
Neutron activation-based gamma scintigraphy in pharmacoscintigraphic evaluation of an Egalet® constant-release drug delivery system by Janne Marvola; Hanna Kanerva; Lillian Slot; Maija Lipponen; Tommi Kekki; Heikki Hietanen; Sirpa Mykkänen; Kari Ariniemi; Kai Lindevall; Martti Marvola (3-10).
This paper is a report from a pharmacoscintigraphic study with an Egalet® constant-release system containing caffeine and natural abundance samarium oxide. First the formulation was tested in vitro to clarify integrity during irradiation in the nuclear reactor. Then six healthy male volunteers were enrolled into the in vivo study. The in vitro release of caffeine obeyed all the time linear zero-order kinetics. The in vivo release of radioactive Sm2O3 consisted of three consequent linear phases with different slopes. The release rate was fastest while the product was in the small intestine and slowest when the product was in the descending colon. In terms of the bioavailability of caffeine, the most important factor seemed to be the residence time in the ascending and transverse colon. A long residence time in these sections led to high AUC values for caffeine.
Keywords: Gamma scintigraphy; Neutron activation; Samarium; Imaging; Controlled release; In vitro–in vivo correlation;
Nasal insulin delivery in the chitosan solution: in vitro and in vivo studies by Shaoyun Yu; Ying Zhao; Fenglan Wu; Xuan Zhang; Wanliang Lü; Hua Zhang; Qiang Zhang (11-23).
The effects of chitosan concentrations, osmolarity, medium and absorption enhancers in the chitosan solution on nasal insulin delivery were studied in vitro and in vivo. The penetration of insulin through the mucosa of rabbit nasal septum was investigated by measuring the transmucosal flux in vitro, while the nasal absorption of insulin in vivo was assessed by the efficiency in lowering the blood glucose levels in normal rats. It was demonstrated that increasing concentrations of chitosan up to 1.5% (w/v) caused an increase in the permeability of insulin across the nasal mucosa. Insulin given intranasally in hypo- or hyperosmotic formulation showed a higher hypoglycemic effect than insulin delivered in isoosmotic formulation. Insulin formulation in chitosan solution prepared with deionized water brought to a higher relative pharmacological bioavailability (Fr) value than that prepared with 50 mM pH 7.4 phosphate buffer. A formulation containing both 1% chitosan and 0.1% ethylenediaminetetraacetic acid (EDTA), 5% polysorbate 80 (Tween 80) or 1.2% β-cyclodextrin (β-CD) did not lead to a higher Fr than insulin formulated with 1% chitosan alone. The formulation containing both 5% hydroxypropyl-β-cyclodextrin (HP-β-CD) and 1% chitosan was more effective at reducing blood glucose levels than the formulation containing 5% HP-β-CD or 1% chitosan alone. The studies indicated that chitosan concentrations, osmolarity, medium and absorption enhancers in chitosan solution have significant effect on the insulin nasal delivery. The results of in vitro experiments were in good agreement with that of in vivo studies.
Keywords: Nasal delivery; Insulin; Chitosan; Permeability; Bioavailability; Rats;
Factors governing the in vivo tissue uptake of transferrin-coupled polyethylene glycol liposomes in vivo by Hiroto Hatakeyama; Hidetaka Akita; Kazuo Maruyama; Tetsuya Suhara; Hideyoshi Harashima (25-33).
Liposomes, coated with transferrin (Tf)-coupled polyethylene glycol are considered to be potent carriers for drug delivery to various organs via receptor-mediated endocytosis. Since Tf receptors were ubiquitously expressed in various organs, additional perturbation of the liposomes such as regulation of the size may be required to exhibit the tissue selectivity. In the present study, the effect of size on the uptake of transferrin-coupled polyethylene glycol liposomes (Tf-PEG-L) to various organs was investigated. In liver and brain, Tf-dependent uptake was found to be dependent on the size of the liposomes used. In small liposomes with a diameter of 60–80 nm, Tf-PEG-L was taken up to these organs more efficiently than PEG-L. This Tf-dependent uptake for small liposomes decreased by the high dose administration, suggested that Tf-PEG-L is taken up via Tf receptor-mediated endocytosis even under the physiological condition, in which plasma concentration of endogenous Tf remains high. On the other hand, Tf receptor-mediated uptake was also observed in the heart, but size-dependency was not observed in this case. Collectively, these results indicate that size dependency in the uptake of Tf-PEG-L is tissue-dependent and therefore, controlling the size of Tf-PEG-L may be useful for the success of tissue targeting.
Keywords: Transferrin; Liposomes; Receptor-mediated endocytosis; Tissue uptake;
Development and in vitro evaluation of furosemide transdermal formulations using experimental design techniques by Gregorios G Agyralides; Paraskevas P Dallas; Dimitrios M Rekkas (35-43).
The in vitro skin permeation of furosemide, a commonly used loop diuretic, through human epidermis, as a preliminary step towards the development of a transdermal therapeutic system, was examined. A screening study was carried out, in order to estimate the effects of the type, the concentration of enhancer and the concentration of gelling agent on the cumulative amount of furosemide permeated through human epidermis, using a 33 factorial design. The type and the concentration of enhancer were further evaluated as they were found to affect significantly furosemide permeation. In order to further increase the amount of the drug permeated, the combination of two enhancers, Azone® and oleyl alcohol, at three concentration levels was employed, using an optimization technique. The results indicated that higher amounts of furosemide permeated were observed when Azone® was used at 5.0–6.5% (v/v) and oleyl alcohol at 7.5–9% (v/v), in the gels used. These formulations seem to be suitable for possible transdermal delivery of furosemide for pediatric use.
Keywords: Furosemide; Transdermal; Experimental design; Penetration enhancer; Gel;
The depolymerization of chitosan: effects on physicochemical and biological properties by Shirui Mao; Xintao Shuai; Florian Unger; Michael Simon; Dianzhou Bi; Thomas Kissel (45-54).
Chitosan has been extensively used as an absorption enhancer for macromolecules and as gene delivery vehicle. Both properties are molecular weight (MW) dependent. Here, we investigate factors affecting the oxidative depolymerization of chitosan and physicochemical properties of the resulting polymer fractions including their cytotoxicity. The molecular weight of the depolymerized chitosan was influenced by the initial concentration and the source of chitosan. At constant initial concentrations, the molecular weight decreased linearly with the chitosan/NaNO2 ratio and was a function of logarithm of the reaction time. Chitosan with larger molecular weight was more sensitive to depolymerization. No structural change was observed during the depolymerization process by infrared and proton nuclear magnetic resonance spectroscopy. In addition, thermal properties of chitosan fragments were studied by thermal gravimetric analysis and it was found that the decomposition temperature was molecular weight dependent. Furthermore, the solubility of different molecular weight chitosan was assayed as a function of pH and it increased with decreasing molecular weight. The cytotoxicity of chitosan was concentration dependent but almost molecular weight independent according to MTT assay using L929 cell line recommended by USP26. In summary, low molecular weight fractions of chitosan may potentially useful for the design of drug delivery systems due to the improved solubility properties.
Keywords: Chitosan; Depolymerization; Intrinsic viscosity; Solubility; Cytotoxicity;
Evaluation of SCF-engineered particle-based lactose blends in passive dry powder inhalers by Helena Schiavone; Srinivas Palakodaty; Andy Clark; Peter York; Stelios T Tzannis (55-66).
The objective of this study was to assess the performance of SCF-engineered budesonide and albuterol sulfate powder blends in passive dry powder inhalers (DPI) relative to micronized drug blends. A number of lactose grades for inhalation were screened and the appropriate carrier and drug-to-lactose blending ratio were selected based on drug content and emitted dose uniformity. Aerosol performance was characterized by Andersen cascade impaction. Blend formulations of SEDS (solution enhanced dispersion by supercritical fluids) budesonide and albuterol exhibited a significant drug content uniformity (7–9% RSD) improvement over micronized drug blends (16–20% RSD). Further, the SEDS formulations demonstrated higher emitted dose and reduced emitted dose variability (10–12% RSD) compared to micronized powders (21–25% RSD) in the Turbospin, albeit without significant enhancement of the fine particle fraction. In contrast, SEDS powders exhibited increased fine particle fractions over micronized blends in the Clickhaler; improvements were more pronounced with albuterol sulfate. The performance enhancements observed with the SEDS powders are attributed to their increased surface smoothness and reduced surface energy that are presumed to minimize irreversible drug–carrier particle interactions, thus resulting in more efficient drug detachment from the carrier particle surface during aerosolization. As demonstrated for budesonide and albuterol, SEDS may enhance performance of lactose blends and thus provide an attractive particle engineering option for the development of blend formulations for inhalation delivery.
Keywords: Supercritical fluids; Micronization; Lactose blends; Dry powder inhaler; Pulmonary delivery;
Influence of lipolysis and droplet size on tocotrienol absorption from self-emulsifying formulations by Siew Ping Yap; Kah Hay Yuen (67-78).
A single dose comparative bioavailability study was conducted to evaluate the bioavailability of tocotrienols from two self-emulsifying formulations, one of which produced an emulsion that readily lipolysed under in vitro condition (SES-A), while the other produced a finer dispersion with negligible lipolysis (SES-B) in comparison with that of a non-self-emulsifying formulation in soya oil. The study was conducted according to a three-way crossover design using six healthy human volunteers. Statistically significant differences were observed between the logarithmic transformed peak plasma concentration (C max) and total area under the plasma concentration–time curve (AUC0–∝) values of both SES-A and -B compared to NSES-C indicating that SES-A and -B achieved a higher extent of absorption compared to NSES-C. Moreover, the 90% confidence interval of the AUC0–∝ values of both SES-A and -B over those of NSES-C were between 2–3 suggesting an increase in bioavailability of about two–three times compared to NSES-C. Both SES-A and -B also achieved a faster onset of absorption. However, both SES-A and -B had comparable bioavailability, despite the fact that SES-B was able to form emulsions with smaller droplet size. Thus, it appeared that both droplet sizes as well as the rate and extent of lipolysis of the emulsion products formed were important for enhancing the bioavailability of the tocotrienols from the self-emulsifying systems.
Keywords: Tocotrienols; Self-emulsifying systems; Lipolysis; Droplet sizes;
Validation of an ocular microdialysis technique in rabbits with permanently implanted vitreous probes: systemic and intravitreal pharmacokinetics of fluorescein by Banmeet S Anand; Harisha Atluri; Ashim K Mitra (79-88).
The purpose of this work is to validate a novel ocular microdialysis sampling technique in rabbits with permanently implanted vitreous probes. This objective is achieved by studying the vitreous pharmacokinetics of fluorescein following systemic and intravitreal administration. The rabbits were divided into two groups (groups I and II) based on whether or not they were allowed a recovery period following surgical implantation of probes. The integrity of the blood-retinal barrier was determined by the vitreal protein concentrations and the fluorescein permeability index. Vitreal protein concentrations returned to baseline 48 h after probe implantation and therefore experiments were conducted 72 h post-implantation of probes in rabbits where recovery period was allowed. The permeability indices for fluorescein after systemic administration in group I (without recovery period) and group II (with recovery period) indicated that the integrity of the blood-retinal barrier was maintained and were found out to be 0.55 ± 0.27 and 0.71 ± 0.38%, respectively, for the vitreous chamber. Following microdialysis probe implantation in the group II rabbits, the blood-retinal barrier integrity was not compromised. A novel microdialysis technique in rabbits with permanently implanted probes for studying the pharmacokinetics of posterior segment has been developed and characterized.
Keywords: Conscious; Microdialysis; Fluorescein; Ocular; Blood ocular barriers; Posterior segment;
Solid state NMR perspective of drug–polymer solid solutions: a model system based on poly(ethylene oxide) by Deborah M Schachter; Jincheng Xiong; Gloria C Tirol (89-101).
Poly(ethylene oxide) (PEO) was tested as a polymer matrix for solid dispersion to enhance drug bioavailability. Solid state nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were utilized to characterize the high miscibility between PEO and ketoprofen, a model for crystalline drugs with poor water solubility. The experimental data demonstrated that ketoprofen in the melt-processed blend formed a complete molecular dispersion within the amorphous domain of PEO, resulting in high molecular mobility of ketoprofen in the melt-processed blend that leads to enhanced dissolution rate of ketoprofen in aqueous media. Hydrogen bonds between the carboxylic group of ketoprofen and the ether oxygen of PEO, as detected by solid-state NMR, are the likely source for the high miscibility between ketoprofen and PEO. Such drug/polymer molecular interactions promote dispersion of ketoprofen into amorphous phase of PEO at temperatures well below melting points of both crystalline ketoprofen and PEO. Consequently, melt-processing temperatures can be reduced significantly to avoid thermal degradation. The processing conditions can be also flexible while maintaining reproducibility of the physico-chemical properties of the blend. Furthermore, the high degree of drug/polymer molecular interactions stabilizes the morphology of the blend during storage.
Keywords: Poly(ethylene oxide); Solid state NMR; Solid dispersion; Solid state characterization; Bioavailability; Melt extrusion;
Paclitaxel loaded poly(l-lactic acid) (PLLA) microspheres by Richard T Liggins; Helen M Burt (103-106).
The kinetics of solvent removal in microsphere preparation and their effect on the morphology and release characteristics of paclitaxel-loaded PLLA microspheres were determined. Microspheres were analyzed by SEM and DSC and in vitro paclitaxel release was monitored by HPLC. During manufacture, dichloromethane evaporated at a constant rate, which increased with dispersion stirring speed and decreased with increasing paclitaxel content. Paclitaxel-loaded microspheres had a dimpled surface, due to surface deposition of the drug, while controls were smooth. In the formation of larger microspheres, the deposition of drug in the surface slowed the solidification process resulting in drug-loading dependent thermal properties. Paclitaxel release did not follow diffusion kinetics, rather it was characterized by a large burst followed by a linear phase. We speculate that non-uniform (surface-rich) drug distribution in the microspheres may contribute to the deviation from the theoretical pattern of kinetics for diffusion from a sphere.
Keywords: Drug release kinetics; Solvent evaporation; Thermal properties; Paclitaxel; Microsphere;
Hydration of an amphiphilic excipient, Gelucire® 44/14 by A Svensson; C Neves; B Cabane (107-118).
The incorporation of drugs into Gelucires has been reported to increase the dissolution rate of poorly soluble drugs, often leading to improved drug bioavailability. In pharmaceutical applications, it is important to know how the excipient interacts with the drug, and how the mixture behaves during manufacturing, storage as well as during administration. The uptake of water by an amphiphilic excipient, Gelucire® 44/14, has been investigated in two ways: storage in humid air and addition of liquid water. During exposure to humid air, the uptake goes in stages that correspond to the dissolution of the components of the excipient, starting with the most hydrophilic ones: glycerol, then polyethylene glycol (PEG), PEG esters (PEG monolaurate and PEG dilaurate), and finally glycerides (trilaurin). At each stage, the remaining crystals are in equilibrium with an interstitial solution made of water and the dissolved components. In this range of hydrations, the total uptake is close to the sum of the equilibrium hydrations of the components. In the pharmaceutical formulation, the active ingredient could dissolve in the liquid phase. At larger hydrations, obtained through addition of liquid water, the state of Gelucire® 44/14 differs from those of its components. Gelucire® 44/14 forms a lamellar phase and this phase melts at 30 °C whereas the pure PEG esters form hexagonal and cubic mesophases. The cubic mesophases do not melt until the temperature exceeds 40 °C. At body temperature, all crystals in Gelucire® 44/14 melt to an isotropic fluid as soon as the total water content exceeds 5%. Therefore the formulation of amphiphilic excipients can be optimized to avoid the formation of mesophases that impede dissolution of the excipient at body temperature.
Keywords: Gelucire® 44/14; Phase diagram; Hydration; Dissolution; Mesophases; PEG esters; DVS; SAXS; WAXS;
Determination of tackiness of chitosan film-coated pellets exploiting minimum fluidization velocity by M Fernández Cervera; J Heinämäki; E Räsänen; O Antikainen; O.M Nieto; A Iraizoz Colarte; J Yliruusi (119-127).
The tackiness of aqueous chitosan film coatings and effects of anti-sticking agents on sticking tendency, were evaluated. A novel rapid method exploiting minimum fluidization velocity to determine tackiness was introduced and tested. The pressure difference over the miniaturized fluidized-bed was precisely recorded as a function of velocity of fluidization air. High molecular weight chitosan plasticized with glycerol was used as a film-forming agent. Magnesium stearate, titanium dioxide, colloidal silicon dioxide and glyceryl-1-monostearate (GMS) were studied as anti-sticking agents. Film coatings were performed in a miniaturized top-spray coater. The incorporation of anti-sticking agents led to a clear decrease in tackiness of the chitosan films, and magnesium stearate and GMS were shown the most effective. Film-coated pellets containing magnesium stearate and GMS as an anti-sticking agent were very easily fluidized (showing very low values of minimum fluidization velocity) and were thus classified as the best flowing and the least sticking samples. Both these additives were found anti-sticking agents of choice for aqueous chitosan film coatings. Determination of the experimental minimum fluidization velocity in a fluidized bed, is a useful and sensitive method of measuring the tackiness tendency of film-coated pellets.
Keywords: Chitosan; Aqueous film coating; Pellets; Tackiness; Anti-sticking agents; Minimum fluidization velocity;
In vitro and in vivo evaluation of a melamine dendrimer as a vehicle for drug delivery by Michael F. Neerman; Wen Zhang; Alan R. Parrish; Eric E. Simanek (129-132).
Cell-based and acute and subchronic in vivo toxicity profiles of a dendrimer based on melamine reveal that this class of molecules warrants additional study as vehicles for drug delivery. In cell culture, a substantial decrease in viability was observed at 0.1 mg/mL. For the acute studies, mice were administered 2.5, 10, 40 and 160 mg/kg of dendrimer via i.p. injection. At 160 mg/kg, 100% mortality was seen 6–12 h after injection. For the other cohorts, blood chemistry work revealed no renal damage was taking place at 48 h. Liver enzyme activity nearly doubled for the mice treated at 40 mg/kg suggesting hepatotoxicity. For the subchronic studies, three i.p. injections of 2.5–40 mg/kg of dendrimers were administered at 3-week intervals. No mortality was observed. Forty-eight hours following the last administration, blood chemistry revealed no renal damage, but liver damage was indicated by elevated serum enzyme activity at the highest dose. Histopathological data further confirms that doses up to 10 mg/kg show no hepatic damage at subchronic doses. However, subchronic doses at 40 mg/kg lead to extensive liver necrosis.
Keywords: Dendrimer; Drug delivery; Biocompatibility; In vivo; Toxicity;