International Journal of Pharmaceutics (v.370, #1-2)
Editorial Board (iii).
Effects of automated external lubrication on tablet properties and the stability of eprazinone hydrochloride by Takahiro Yamamura; Tomoaki Ohta; Toshinari Taira; Yutaka Ogawa; Yasuyuki Sakai; Kunikazu Moribe; Keiji Yamamoto (1-7).
We investigated the advantages of an external lubrication technique for tableting. A newly developed external lubricating system was applied to tableting in a rotary tablet press using magnesium stearate. The resulting tablets were compared with tablets produced by the conventional internal lubrication method, in which lubricant is blended before tableting. As a model API, we chose eprazinone hydrochloride, because it is easily hydrolyzed by alkaline lubricant. The amount of lubricant required to prevent sticking with external lubrication was only 1/13th of that required with internal lubrication. External lubrication increased tablet crushing strength by 40%, without prolonging tablet disintegration time, and improved the residual ratio of eprazinone hydrochloride in tablets stored under stress conditions for 4 weeks by 10%. The distribution of lubricant on the surface of externally lubricated tablets was observed by scanning electron microscopy after the preparation by focused ion beam milling. The lubricant had formed a layer on the tablet surface. At the central part of the tablet surface, this layer was much thinner than at the edges, and remained extremely thin even when there was excess magnesium stearate. This is the first report to describe the distribution of lubricant on the surface of externally lubricated tablets.
Keywords: External lubrication; External lubrication system; Lubricants; Magnesium stearate; Drug stability; Focused ion beam;
Terahertz pulsed imaging and near infrared imaging to monitor the coating process of pharmaceutical tablets by Lene Maurer; Hans Leuenberger (8-16).
Terahertz pulsed imaging (TPI) and near infrared (NIR) imaging were used to non-destructively monitor the coating process of film-coated tablets. Samples that were taken from a pan coater at different time points were analyzed by both methods. TPI provided coating thickness maps over the whole surface of the tablets, determining the thickness of the coating at each point of the sample surface in μm, this way also giving information about the coating uniformity. The growth of the coating during the coating process was shown. NIR imaging did not provide direct thickness values, but by different absorbance values, inter- and intra-tablet differences were shown. Thus, coating thickness information was also obtained in a way that different tablets could be compared. The growth of the coating layer during the process was shown as well. Both methods provided comparable results; and they were able to detect small defects in the coating. With TPI, the whole tablet surface could be scanned; with NIR imaging information about the tablet ends at the center-band was not obtained due to the strong curvature. NIR imaging proved to be better at thinner coating layers and had a higher spatial resolution whereas TPI had the clear advantage that it provided direct thickness values.
Keywords: Near infrared (NIR) imaging; Terahertz pulsed imaging (TPI); Pharmaceutical; Tablet; Coating;
Ultrasonic determination of Young's moduli of the coat and core materials of a drug tablet by Ilgaz Akseli; Douglas C. Becker; Cetin Cetinkaya (17-25).
Many modern tablet presses have system controls that monitor the force exerted to compress the solid oral dosage forms; however this data provides only limited information about the mechanical state of the tablet due to various process and materials uncertainties. A contact pulse/echo ultrasonic scheme is presented for the determination of the local Young's moduli of the coat and the core materials of enteric-coated and monolayer coated tablets. The Young's modulus of a material compacted into solid dosage can be related to its mechanical hardness and, consequently, its dissolution rate. In the current approach, short ultrasonic pulses are generated by the active element of a delay line transducer and are launched into the tablet. The waveforms reflected from the tablet coat–core interface are captured by the same transducer and are processed for determining the reflection and transmission coefficients of the interface from partially overlapping echoes. The Young's moduli of the coat and the core materials are then extracted from these coefficients. The results are compared to those obtained by an air-coupled acoustic excitation study, and good agreement is found. The described measurement technique provides greater insight into the local physical properties of the solid oral dosage form and, as a result, has the potential to provide better hardness-related performance predictability of compacts.
Keywords: Young's modulus; Tablet hardness; Tablet testing; Tablet mechanical properties; Tablet thickness measurements; Ultrasonic techniques;
Chitosan–aprotinin coated liposomes for oral peptide delivery: Development, characterisation and in vivo evaluation by Martin Werle; Hirofumi Takeuchi (26-32).
In order to improve the systemic uptake of therapeutic peptides/proteins after oral administration, the polymer-protease inhibitor conjugate chitosan–aprotinin was synthesised and polyelectrolyte complexes between negatively charged multilamellar vesicles (MLV) and positively charged chitosan–aprotinin conjugate were prepared. It could be demonstrated that chitosan–aprotinin was capable of significantly inhibiting Trypsin in vitro in concentrations of 0.05% and 0.1%, whereas no inhibition was observed in the presence of 0.1% chitosan. The size range of the prepared MLV was between 3 and 4.5 μm and the initially negative zeta potential (ca. −90 mV) of the core liposomes switched to a positive value after polymer coating (ca. +40 mV). Confocal laser microscopy studies showed comparable mucoadhesive properties of chitosan–aprotinin coated MLV and chitosan coated MLV. In comparison to calcitonin in solution, the area above the blood calcium concentration–time curve (AAC) after oral administration of calcitonin loaded chitosan coated MLV to rats increased around 11-fold, and around 15-fold in the case of calcitonin loaded chitosan–aprotinin coated MLV. Data gained in the current study are believed to contribute to the development of novel polymer-protease inhibitor based delivery systems.
Keywords: Oral peptide delivery; Polymer-protease inhibitor conjugate; Liposomes; Calcitonin;
Evaluation of different buffers on plasmid DNA encapsulation into PLGA microparticles by Man Tsuey Tse; Chris Blatchford; H. Oya Alpar (33-40).
Double emulsion solvent evaporation is a widely used method to prepare poly(dl-lactide-co-glycolide) (PLGA) microparticles encapsulating plasmid DNA. There are inherent problems associated with preparing plasmid DNA in this form, in particular the DNA is liable to degrade during manufacture and the resulting powder has low encapsulation efficiencies. This study compares the use of two buffers, 0.1 M NaHCO3 and 0.07 M Na2HPO4 and the effect these have on the encapsulation efficiency and other critical parameters associated with these encapsulated DNA materials. Both buffers preserved the conformation of the original plasmid DNA during the homogenization process, but those made with 0.07 M Na2HPO4 had higher encapsulation efficiencies, as well as smaller diameters, compared with those made with 0.1 M NaHCO3 (encapsulation efficiencies of 40.72–45.65%, and mean volume diameters of 2.96–4.45 μm). Buffers with a range of pH from 5 to 12 were investigated, and it was demonstrated that pH 9 was the point at which the highest amount of supercoiled DNA was balanced with the highest encapsulation efficiency. To simulate in vitro release, it was shown that microparticles made with 0.07 M Na2HPO4 had lower DNA release rates than those made with 0.1 M NaHCO3. These results demonstrate that the use of different buffers can aid in retaining the conformation of plasmid DNA, and can also modulate the amount of DNA encapsulated and the release profiles of microparticles.
Keywords: Microparticle; Plasmid DNA; Buffer; PLGA; pH;
Development of fixed dose combination tablets containing zidovudine and lamivudine for paediatric applications by E. Kayitare; C. Vervaet; J.D. Ntawukulilyayo; B. Seminega; Van Bortel; J.P. Remon (41-46).
In view of the lack of suitable paediatric antiretroviral formulations on the market, a novel fixed dose combination (FDC) tablet containing 300 mg zidovudine (AZT) and 160 mg lamivudine (3TC) was developed to improve dosing accuracy and allow flexible drug dosing in function of the body weight of paediatric HIV patients as recommended by WHO.Rectangular tablets with multiple fraction bars were designed and each tablet can be broken into 8 subunits, each subunit containing a drug dose corresponding to a body weight of 5 kg. These fast-disintegrating subunits can easily be administered to children after dispersion in a liquid or mixing with food. In vitro quality control of the FDC tablets was determined and a crossover bioavailability study using 18 adult volunteers was performed after oral administration of the novel FDC tablet and a Duovir tablet.The results of the study showed that the novel tablets as well as its subunits disintegrated fast (<20 s). After 30 min dissolution, AZT and 3TC released from Duovir® and the novel tablets was above 95%, the similarity factors f2 were above 50 for both AZT and 3TC. A tablet breakability test showed low weight variability (125.1 ± 5 mg, R.S.D. = 4.4%), with limited weight loss (0.3%). There was no significant difference in pharmacokinetic parameters (C max, t max and AUC0–12 h values) between Duovir and the novel tablets formulated for paediatric applications.
Keywords: Antiretroviral fixed dose combination; Paediatric drug formulations;
Encapsulated zinc salt increases the diffusion of protein through PLG films by Susanne Fredenberg; Mats Reslow; Anders Axelsson (47-53).
The use of microspheres and nanospheres of poly(d,l-lactide-co-glycolide) (PLG) as a controlled-release drug delivery system has been the subject of great interest for at least two decades within the field of pharmaceuticals. Salts of zinc and other divalent cations are sometimes co-encapsulated in PLG particles to control the pH or to stabilize encapsulated proteins or peptides. Zinc salts are known to affect pore formation and other processes that may lead to the release of an encapsulated drug. In this study the effect of encapsulated zinc acetate on protein diffusion through PLG films was investigated. PLG films, with and without encapsulated zinc acetate, were degraded in Hepes buffer for different periods of time. The films were subsequently subjected to various kinds of analyses: diffusion properties (using a diffusion cell), porosity (using scanning electron microscopy) and thickness (using light microscopy and an image-analysis program). Encapsulated zinc acetate had a considerable effect and increased the diffusion coefficient of lysozyme through PLG films degraded for 18 days or longer. Films containing zinc acetate became porous, while those without zinc acetate only developed cavities on the surface. Zinc salts may thus be used as release-modifying agents. This effect should be considered when using zinc salts as protein stabilizers or pH neutralizers.
Keywords: Poly(d,l-lactide-co-glycolide); Diffusion; Degradation; Pore formation; Zinc salt; Controlled release;
Development of tablets containing probiotics: Effects of formulation and processing parameters on bacterial viability by Srikanjana Klayraung; Helmut Viernstein; Siriporn Okonogi (54-60).
The probiotic products available in the market nowadays are mostly in the form of liquid or semisolid formulations which show low cell viability after oral administration, mainly because the bacteria do not survive the harsh conditions in the stomach. The development of suitable dry dosage forms enable higher bacterial survival and consequently is the main aim of the present study. An anticipated advantage is that due to the low water-activity lyophilized bacterial cells will preserve their viability. Further, by a proper selection of a tablet forming matrix, it is foreseen that the entrapped bacteria are protected against the low pH in the stomach. In this study, the effects on bacterial survival in tablets were investigated concerning compression force, matrix forming excipients such as hydroxypropyl methylcellulose phthalate (HPMCP) or other swelling agents. The results showed that the proportion of matrix forming excipients in tablets and the compression force affected the properties of probiotic tablets in terms of tensile strength and disintegration as well as the survival of the bacteria. The tensile strength of the tablets increased with increase of HPMCP content. Tablets manufactured with high compression force showed a slow disintegration time and high bacterial cell viability (more than 80%). Incorporation of sodium alginate in the tablets resulted in higher cell survival in simulated GI fluid (>90%) and a suitable disintegration time (approximately 5 h). By a proper design of the formulation, tablets with a fast disintegration time and a high preservation of bacterial cell viability were developed.
Keywords: Probiotic; Tablet; Viability; Stability; Sodium alginate; HPMCP;
Overcoming the nail barrier: A systematic investigation of ungual chemical penetration enhancement by M.B. Brown; R.H. Khengar; R.B. Turner; B. Forbes; M.J. Traynor; C.R.G. Evans; S.A. Jones (61-67).
This study investigated the in vitro nail permeability of penetrants of varying lipophilicity—caffeine (CF, log P −0.07), methylparaben (MP, log P 1.96) and terbinafine (TBF, log P 3.3) and the effect of 2 novel penetration enhancers (PEs), thioglycolic acid (TA) and urea hydrogen peroxide (urea H2O2) on their permeation. Studies were conducted using full thickness human nail clippings and ChubTur® diffusion cells and penetrants were applied as saturated solutions. The rank order of steady-state penetrant flux through nails without PE application (MP > CF > TBF) suggested a greater sensitivity to penetrant molecular weight rather than log P. TA increased the flux of CF and MP ∼4- and ∼2-fold, respectively, whilst urea H2O2 proved ineffective at enhancing permeability. The sequential application of TA followed by urea H2O2 increased TBF and CF flux (∼19- and ∼4-fold, respectively) but reversing the application order of the PEs was only mildly effective at increasing just MP flux (∼2-fold). Both nail PEs are likely to function via disruption of keratin disulphide bonds and the associated formation of pores that provide more ‘open’ drug transport channels. Effects of the PEs were penetrant specific, but the use of a reducing agent (TA) followed by an oxidising agent (urea H2O2) dramatically improved human nail penetration.
Keywords: Onychomycosis; Drug permeation; Nail; Ungual; Penetration enhancers;
HO-1-u-1 model for screening sublingual drug delivery—Influence of pH, osmolarity and permeation enhancer by Yanfeng Wang; Zhong Zuo; Moses S.S. Chow (68-74).
HO-1-u-1 (Ueda-1) is a human tumor cell line established from human sublingual squamous cell carcinoma. In previous study, HO-1-u-1 cell line was grown on cell culture inserts and utilized as in vitro model for screening sublingual drug delivery. The aim of current study was to further investigate the effects of pH, osmolarity and permeation enhancer, sodium glycodeoxycholate (GDC) on the permeability of three β-blockers with different lipophilicities. The cytotoxicity was evaluated by MTS/PES assay. The permeability studies were carried out using the cell culture model and compared with that obtained from fresh porcine sublingual mucosa. The results showed the enhancement effects caused by pH, osmolarity and GDC were highly lipophilicity-dependent and in the order atenolol > metoprolol > propranolol. The apparent permeability coefficients (P app) of all the three β-blockers were significantly increased by increasing pH. However, less enhancing effects were observed by non-physiological osmolarity or the presence of GDC in permeability study using both cell culture and porcine sublingual mucosa. The present results suggested that the HO-1-u-1 cell culture model maybe a useful and effective in vitro model for evaluating the enhancement effects and mechanism in sublingual drug delivery.
Keywords: HO-1-u-1; Sublingual delivery; β-Blocker; pH; Osmolarity; Enhancer;
In vitro elution of vancomycin/amikacin/steroid from solvent-free biodegradable scleral plugs by Shih-Jung Liu; Yi-Chuan Kau; Chau-Wei Liaw; Yi-Jie Peng (75-80).
The purpose of this report was to develop solvent-free biodegradable scleral plugs for vancomycin, amikacin and dexamethasone delivery for endophthalmitis treatment. To fabricate a biodegradable plug, polylactide–polyglycolide copolymers were pre-mixed with the drugs. The mixture was then compression molded and sintered to form a scleral plug of 1.4 mm in diameter. An elution method was utilized to characterize the in vitro release characteristics of the antibiotics and the steroids over a 14-day period. The HPLC analysis and bacterial inhibition test showed that biodegradable scleral plugs released a high concentration resulting in significant activity of vancomycin and amikacin (well above the minimum inhibition concentrations) and dexamethasone in vitro, for the period of time needed to treat intraocular infection. A bacterial inhibition test was carried out to determine the relative activity of the released antibiotics. The activities of the eluted vancomycin and amikacin ranged from 69% to 89% and from 66% to 88%, respectively. In addition, the experimental result suggests that one will be able to reduce the drug release rate and prolong the total release period of the plugs by adopting a lower antibiotic/steroid to polymer ratio, increasing the sintering temperature, or increasing the compression pressures.
Keywords: Endophthalmitis; Biodegradable scleral plugs; Polylactide–polyglycolide; Vancomycin; Amikacin; Dexamethasone; In vitro elution; Release characteristics;
A novel zein-based dry coating tablet design for zero-order release by H.X. Guo; Y.P. Shi (81-86).
The purpose of this study was to design zero-order release of dry-coated tablets using pure zein powder, zein granule and zein blend containing two common pharmaceutical excipients such as microcrystalline cellulose (MCC) or starch in different proportions as coating material. The 5-fluorouracil (5-FU) was used as a model drug. The physical characterization and drug release behaviors of dry-coated tablets were investigated. The surface structure of the tablets was examined by a scanning electron microscopy. The correlation coefficient (R) was used as indicator of the best fitting of the zero-order model for drug release. It was found that zein formed a gelatinous layer fast and its network prevented disintegration of the tablet during dissolution process. Zein-based dry coating tablets had good physical properties such as compactibility and friability. All formulations fit the zero-order model well. The mechanism for zero-order release of these dry-coated tablets was solvent penetration into the dosage form and dissolving the drug, the dissolving core formed an apex in the center of the tablets and the drug diffused out. The apex of zein-coated tablets worked as orifice of an osmotic system and released the drug in zero-order profile.
Keywords: Zein; MCC; Starch; Dry-coated tablet; Zero-order release;
Improved absorption and bioactivity of active compounds from an anti-diabetic extract of Artemisia dracunculus L by David M. Ribnicky; Peter Kuhn; Alexander Poulev; Sithes Logendra; Aamir Zuberi; William T. Cefalu; Ilya Raskin (87-92).
An ethanolic extract of Artemisia dracunculus L. (PMI-5011) was shown to be hypoglycemic in animal models for Type 2 diabetes and contains at least 6 bioactive compounds responsible for its anti-diabetic properties. To evaluate the bioavailability of the active compounds, high fat dietary induced obese C57BL/6J male mice were gavaged with PMI-5011 at 500 mg/kg body weight, after 4 h of food restriction. Blood plasma samples (200 uL) were obtained after ingestion, and the concentrations of the active compound in the blood sera were measured by electrospray LC-MS and determined to be maximal 4–6 h after gavage. Formulations of the extract with bioenhancers/solubilizers were evaluated in vivo for hypoglycemic activity and their effect on the abundance of active compounds in blood sera. At doses of 50–500 mg/kg/day, the hypoglycemic activity of the extract was enhanced 3–5-fold with the bioenhancer Labrasol, making it comparable to the activity of the anti-diabetic drug metformin. When combined with Labrasol, one of the active compounds, 2′, 4′-dihydroxy-4-methoxydihydrochalcone, was at least as effective as metformin at doses of 200–300 mg/kg/day. Therefore, bioenhancing agents like Labrasol can be used with multicomponent botanical therapeutics such as PMI-5011 to increase their efficacy and/or to reduce the effective dose.
Keywords: Bioavailability; Botanical; Artemisia; Diabetes; Anti-diabetic; Bioenhancer; Labrasol;
Inhibiting efflux with novel non-ionic surfactants: Rational design based on vitamin E TPGS by Michael F. Wempe; Charles Wright; James L. Little; Janet W. Lightner; Shannon E. Large; George B. Caflisch; Charles M. Buchanan; Peter J. Rice; Vincent J. Wacher; Karen M. Ruble; Kevin J. Edgar (93-102).
Tocopheryl Polyethylene Glycol Succinate 1000 (TPGS 1000) can inhibit P-glycoprotein (P-gp); TPGS 1000 was not originally designed to inhibit an efflux pump. Recent work from our laboratories demonstrated that TPGS activity has a rational PEG chain length dependency. In other recent work, inhibition mechanism was investigated and appears to be specific to the ATPase providing P-gp energy. Based on these observations, we commenced rational surface-active design. The current work summarizes new materials tested in a validated Caco-2 cell monolayer model; rhodamine 123 (10 μM) was used as the P-gp substrate. These results demonstrate that one may logically construct non-ionic surfactants with enhanced propensity to inhibit in vitro efflux. One new surfactant based inhibitor, Tocopheryl Polypropylene Glycol Succinate 1000 (TPPG 1000), approached cyclosporine (CsA) in its in vitro efflux inhibitory potency. Subsequently, TPPG 1000 was tested for its ability to enhance the bioavailability of raloxifene – an established P-gp substrate –in fasted male rats. Animals dosed with raloxifene and TPPG 1000 experienced an increase in raloxifene oral bioavailability versus a control group which received no inhibitor. These preliminary results demonstrate that one may prepare TPGS analogs that possess enhanced inhibitory potency in vitro and in vivo.
Keywords: P-glycoprotein; Vitamin E TPGS; Efflux ratio; Caco-2 cell monolayers; Liquid chromatography–mass spectrometry/mass spectrometry;
Plasticizers in the manufacture of novel skin-bioadhesive patches by Avi Gal; Amos Nussinovitch (103-109).
The effects of plasticizer inclusion (10%, w/w) on roughness, mechanical and adhesive properties of novel skin-bioadhesive patches produced from polyvinyl alcohol and polyvinyl pyrrolidone were studied. Dry, non-adhesive patches became adhesive upon wetting. Roughness profiles of the patches and a skin model were studied, by measuring average values of Ra (recognized as average roughness in practice) and Rz (average of the vertical distances from the highest peak to the lowest valley within five equal sampling lengths). These values ranged from 2.4 to 3.8 μm and from 10.9 to 12.5 μm, respectively. Plasticizers had no significant effect on them. The average Ra obtained for the skin model was six- to eightfold higher than that obtained for the patches. Plasticizer inclusion caused a reduction in patch tensile strength and an increase in its strain at failure—the lower the plasticizer's molecular weight, the greater its effect. Plasticizer inclusion also caused a significant reduction in peeling force: 1.5 ± 0.11 and 2.8 ± 0.13 g force/cm for patches with and without glycerol, respectively. Patch adhesion to the skin also depended on the time elapsed between application and removal. In summary, plasticizer inclusion widened the range of mechanical and adhesive properties of the patches.
Keywords: Plasticizer; Roughness; Mechanical properties; Adhesion; Peeling;
Mechanisms of drug release in citrate buffered HPMC matrices by Samuel R. Pygall; Sarah Kujawinski; Peter Timmins; Colin D. Melia (110-120).
Few studies report the effects of alkalizing buffers in HPMC matrices. These agents are incorporated to provide micro-environmental buffering, protection of acid-labile ingredients, or pH-independent release of weak acid drugs. In this study, the influence of sodium citrate on the release kinetics, gel layer formation, internal gel pH and drug release mechanism was investigated in HPMC 2910 and 2208 (Methocel E4M and K4M) matrices containing 10% felbinac 39% HPMC, dextrose and sodium citrate. Matrix dissolution at pH 1.2 and pH 7.5 resulted in complex release profiles. HPMC 2910 matrices exhibited biphasic release, with citrate increasing the immediate release phase (<60 min) and reducing the extended release. HPMC 2208 matrices were accelerated, but without the loss of extended release characteristics. Studies of early gel layer formation suggested gel barrier disruption and enhanced liquid penetration. pH modification of the gel layer was transitory (<2 h) and corresponded temporally with the immediate release phase. Results suggest that in HPMC 2910 matrices, high initial citrate concentrations within the gel layer suppress particle swelling, interfere with diffusion barrier integrity, but are lost rapidly whereupon drug solubility reduces and the diffusion barrier recovers. These Hofmeister or osmotic-mediated effects are better resisted by the less methoxylated HPMC 2208.
Keywords: Hydroxypropyl methyl cellulose; Hydrophilic matrix; Buffering; Citrate; Drug release; Mechanism;
Inhibition of breast cancer metastasis by dual liposomes to disturb complex formation by Jane Wenzel; Reiner Zeisig; Iduna Fichtner (121-128).
The interaction between tumour cells and blood components, mainly platelets, plays an important role in metastasis. In this study, the anti-metastatic effect of vesicles containing the cytotoxic drug perifosine (OPP) and the haemostatic inhibitor dipyridamole (DIP) was tested. These dual liposomes (DIP/OPP-L) encapsulating up to 400 μg DIP/ml and 6 mM OPP were prepared by extrusion technique. In vitro, DIP/OPP-L significantly inhibited the aggregation of platelets and reduced their adhesion to immobilized MT3 cells by up to 60% and 24.7%, respectively. Complex formation between platelets and tumour cells in vitro was completely prevented by DIP/OPP-vesicles. These combinatory liposomes also inhibited the metastatic capacity of circulating tumour cells by reducing the complex formation with platelets. Formation of lung and extrapulmonary metastases after intravenous administration of MT3 breast cancer cells was significantly reduced when mice were treated with a single intravenous dose of DIP/OPP-L containing 100 nmol lipid 6 h before tumour cell inoculation.
Keywords: Breast cancer; Metastasis; Liposomes; Platelet aggregation; Dipyridamole; Complex formation;
Design and in vivo evaluation of an indapamide transdermal patch by Changshun Ren; Liang Fang; Lei Ling; Qiang Wang; Sihai Liu; LiGang Zhao; Zhonggui He (129-135).
The aim of the present study was to develop and evaluate a novel drug-in-adhesive transdermal patch system for indapamide. Initial in vitro experiments were conducted to optimize formulation parameters prior to transdermal delivery in rats. The effects of the type of adhesive and the content of permeation enhancers on indapamide transport across excised rat skin were evaluated. The results indicated that DURO-TAK® adhesive 87-2852 is a suitable and compatible polymer for the development of transdermal drug delivery systems for indapamide. The final formulation contained 4% N-dodecylazepan-2-one, 6% l-menthol and 3% isopropyl myristate. For in vivo studies patch systems were administered transdermally to rats while orally administered indapamide in suspension was used as a control. The PK parameters, such as the maximum blood concentration (C max), time to reach the peak blood concentration (T max), mean residence time (MRT), area under the curve (AUC0–t ) and terminal elimination half-life (T 1/2) were significantly (p < 0.05) different following transdermal administration compared with oral administration. In contrast to oral delivery, a sustained activity was observed over a period of 48 h after transdermal administration. This sustained activity was due to the controlled release of drug into the systemic circulation following transdermal administration.
Keywords: Drug-in-adhesive transdermal patch; Indapamide; In vitro; In vivo; Rat;
Targeted delivery of methotrexate to skeletal muscular tissue by thermosensitive magnetoliposomes by Lin Zhu; Zongli Huo; Lulu Wang; Xin Tong; Ying Xiao; Kunyi Ni (136-143).
Thermosensitive magnetoliposomes (TMs) encapsulated with methotrexate (MTX) were prepared with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol by reverse-phase evaporation. Encapsulation efficiency of MTX and hydrophilic magnetite Fe2O3-glu, liposome particle size, ζ-potential, and in vitro and in vivo drug release were studied. More than 80% of loaded MTX was released from TMs within 30 min when the environmental temperature increased from 37 °C to 41 °C, while 60% of the drug was remained inside TMs for up to 24 h at 37 °C. Furthermore, the pharmacokinetics and tissue distribution study showed that TMs significantly increased the accumulation of MTX in the skeletal muscular tissue when exposed to an external constant magnetic field and heated to 41 °C compared to the absence of the magnetic field and heating. Therefore, the results in this study suggested that TMs prepared by reverse-phase evaporation can archive a good magnetic targeting effect and fast drug release in response to hyperthermia, which implies their great potential of application in cancer therapy.
Keywords: Thermosensitive; Magnetoliposomes; Targeted delivery; Liposome; Methotrexate;
Scintigraphic evaluation of colon targeting pectin–HPMC tablets in healthy volunteers by L.A. Hodges; S.M. Connolly; J. Band; B. O’Mahony; T. Ugurlu; M. Turkoglu; C.G. Wilson; H.N.E. Stevens (144-150).
The in vivo evaluation of colon-targeting tablets was conducted in six healthy male volunteers. A pectin–hydroxypropyl methylcellulose coating was compressed onto core tablets labelled with 4 MBq 99mTc-DTPA. The tablets released in the colon in all subjects; three in the ascending colon (AC) and three in the transverse colon (TC). Tablets that released in the TC had reached the AC before or just after food (Group A). The other three tablets released immediately upon AC entry at least 1.5 h post-meal (Group B). Release onset for Group B was earlier than Group A (343 min vs 448 min). Group B tablets exhibited a clear residence period at the ileocaecal junction (ICJ) which was not observed in Group A. Prolonged residence at the ICJ is assumed to have increased hydration of the hydrogel layer surrounding the core tablet. Forces applied as the tablets progressed through the ICJ may have disrupted the hydrogel layer sufficiently to initiate radiolabel release. Conversely, Group A tablets moved rapidly through the AC to the TC, possibly minimising contact times with water pockets. Inadequate prior hydration of the hydrogel layer preventing access of pectinolytic enzymes and reduced fluid availability in the TC may have retarded tablet disintegration and radiolabel diffusion.
Keywords: Compression-coated tablets; Colon-specific drug delivery; Gamma scintigraphy; HPMC; Pectin;
In vitro and ex vivo bioadhesivity analysis of polymeric intravaginal caplets using physicomechanics and computational structural modeling by Valence M.K. Ndesendo; Viness Pillay; Yahya E. Choonara; Riaz A. Khan; Leith Meyer; Eckhart Buchmann; Uwe Rosin (151-159).
The in vitro and ex vivo bioadhesivity of polyacrylic acid (PAA)-based intravaginal caplets was explored from a physicomechanical and chemometrical structural modeling viewpoint. An Extreme Vertices Mixture Design was constructed for analyzing the bioadhesivity of 11 matrices that were optimized. Two sets of crosslinked PAA-based matrices comprising either allyl-sucrose (AS-PAA) or allyl-penta-erythritol (APE-PAA) were explored. Powders were compressed into caplet-shaped matrices and rotational rheological analysis was performed on hydrated polymeric blends. Caplets were evaluated for bioadhesiveness using a simulated vaginal membrane (SVM) with optimized caplets further tested using freshly excised rabbit vaginal tissue. The SVM and caplets were hydrated in simulated vaginal fluid before bioadhesivity testing using a texture analyzer to determine the rupture force between the membranous substrates and hydrated caplets. Computational and molecular structural modeling deduced transient sol–gel mechanisms, chemical interactions and inter-polymeric interfacing during caplet-substrate bioadhesion. Peak adhesive force (PAF) and work of adhesion (AUCFD) values for the APE-PAA caplets (1.671 ± 0.232 N; 0.0010 ± 0.0002 J) were higher than the AS-PAA caplets (1.168 ± 0.093 N; 0.00030 ± 0.0001 J) revealing superior bioadhesiveness. Similarly, rheological analysis revealed APE-PAA blends with higher viscosity and shear stress values (9 × 105 mPa/180 Pa). The optimized APE-PAA matrices adhered appreciably to rabbit vaginal tissue (PAF = 0.883 ± 0.083 N; AUCFD = (0.0003 ± 3.5355) × 10−5 J). Results strongly suggest that the approach may be useful for assessing the bioadhesivity of intravaginal matrices on ex vivo rabbit vaginal tissue with data further supported by molecular structural analysis and energy-dependant bioadhesivity modeling.
Keywords: Bioadhesive polymers; Intravaginal drug delivery; Textural profile analysis; Bioadhesion; Structural modeling; Excised rabbit vaginal tissue;
Novel drug delivery devices for providing linear release profiles fabricated by 3DP by Deng-Guang Yu; Christopher Branford-White; Zhong-Hui Ma; Li-Min Zhu; Xiao-Yan Li; Xiang-Liang Yang (160-166).
Novel doughnut-shaped multi-layered drug delivery devices (DDDs) were developed with local variations of the drug and release-retardant material for providing linear release profiles. Based on computer-aided design models, different DDDs containing acetaminophen as a model drug, hydroxypropyl methylcellulose as matrix and ethyl cellulose (EC) as a release-retardant material were prepared automatically using a three-dimensional printing (3DP) system. In vitro dissolution assays demonstrated that all the 3DP DDDs had with different diameters, heights, concentrations of EC and central hole diameters were able to give linear release profiles. Morphological and erosion studies showed that acetaminophen was released through a simultaneous surface erosion process involving the outer peripheries and inner apertures. The barrier layers on both bases of DDDs had good adhesion strength with the drug-contained regions and offered consistent release retardation for the whole duration of the dissolution process. The release time periods of the DDDs were dependent on the annular thicknesses or the passes of binder solution containing a release-retardant material. The dosage of the DDD can be adjusted independently by changing the heights of the DDDs. Thus, 3DP is capable of offering novel strategies for developing DDDs with complex design features for desired drug release profiles.
Keywords: Three-dimensional printing; Drug delivery devices; Design features; Linear release profiles; Surface erosion; Doughnut shape; Multi-layers;
Enhancement of oral bioavailability of an HIV-attachment inhibitor by nanosizing and amorphous formulation approaches by Michael G. Fakes; Blisse J. Vakkalagadda; Feng Qian; Sridhar Desikan; Rajesh B. Gandhi; Chiajen Lai; Alice Hsieh; Miriam K. Franchini; Helen Toale; Jonathan Brown (167-174).
BMS-488043 is an HIV-attachment inhibitor that exhibited suboptimal oral bioavailability upon using conventional dosage forms prepared utilizing micronized crystalline drug substance. BMS-488043 is classified as a Biopharmaceutics Classification System (BCS) Class-II compound with a poor aqueous solubility of 0.04 mg/mL and an acceptable permeability of 178 nm/s in the Caco2 cell-line model. Two strategies were evaluated to potentially enhance the oral bioavailability of BMS-488043. The first strategy targeted particle size reduction through nanosizing the crystalline drug substance. The second strategy aimed at altering the drug's physical form by producing an amorphous drug. Both strategies provided an enhancement in oral bioavailability in dogs as compared to a conventional formulation containing the micronized crystalline drug substance. BMS-488043 oral bioavailability enhancement was ∼5- and 9-folds for nanosizing and amorphous formulation approaches, respectively. The stability of the amorphous coprecipitated drug prepared at different compositions of BMS-488043/polyvinylpyrrolidone (PVP) was evaluated upon exposure to stressed stability conditions of temperature and humidity. The drastic effect of exposure to humidity on conversion of the amorphous drug to crystalline form was observed. Additionally, the dissolution behavior of coprecipitated drug was evaluated under discriminatory conditions of different pH values to optimize the BMS-488043/PVP composition and produce a stabilized, amorphous BMS-488043/PVP (40/60, w/w) spray-dried intermediate (SDI), which was formulated into an oral dosage form for further development and evaluation.
Keywords: BCS Class-II; HIV-attachment inhibitor; Spray drying; Amorphous; Nanosuspension; Spray-dried intermediate (SDI); BMS-488043;
Nanosized bicalutamide and its molecular structure in solvents by Yuan Le; Hua Ji; Jian-Feng Chen; Zhigang Shen; Jimmy Yun; Min Pu (175-180).
Nanosized bicalutamide particles have been obtained by anti-solvent precipitation after screened DMSO and EtOH as co-solvents. The produced nanoparticles have been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR), X-ray diffraction (XRD) and a dissolution test. The mean particle size of bicalutamide is about 450 nm with a narrow distribution. The results of the dissolution test show that dissolution rate of the produced nanoparticles are higher than that of the raw material. Besides, DFT calculations of the bicalutamide conformers have firstly been presented. It is found that the calculated geometry structure of lower-energy conformer is very similar to the experimental structure existing within the crystal lattice. The solvent effects have been taken into account based on the polarizable continuum model (PCM). The computed results appear that the introduction of dielectric medium has obvious effect on the molecular geometry of bicalutamide.
Keywords: Bicalutamide; Nanoparticles; Anti-solvent precipitation; Conformers; Solvent effects;
Lecithin based nanoemulsions: A comparative study of the influence of non-ionic surfactants and the cationic phytosphingosine on physicochemical behaviour and skin permeation by Sonja Hoeller; Andrea Sperger; Claudia Valenta (181-186).
Charged drug delivery systems are interesting candidates for the delivery of drugs through skin. In the present study, it was possible to create negatively and positively charged oil/water nanoemulsions by using sucrose laureate and polysorbate 80 as non-ionic surfactants. The positively charged nanoemulsions were generated by adding cationic phytosphingosine (PS). The relationship between the physicochemical properties of the nanoemulsions was shown by particle size and zeta potential measurements. These properties were dependent on the type of non-ionic surfactant and the concentration of PS. Furthermore the cationic PS had a positive impact on the skin permeation rates (flux) of the incorporated model drugs fludrocortisone acetate and flumethasone pivalate. An enhancement factor between 1.1 and 1.5 was obtained in relation to the control. The interaction of pre-impregnated porcine skin with positively and negatively charged nanoemulsions was confirmed by DSC analysis. The generated DSC-curves showed a slight difference in the phase transition temperature assigned to the characteristic lipid transition. However, it was not possible to assign the effect to one of the ingredients in the multicomponent system.
Keywords: Nanoemulsions; Sucrose ester; Polysorbate 80; Particle size; Zeta potential skin permeation; DSC;
Studies on bioadhesive PLGA nanoparticles: A promising gene delivery system for efficient gene therapy to lung cancer by Weiwei Zou; Chunxi Liu; Zhijin Chen; Na Zhang (187-195).
The study aimed to design novel bioadhesive PLGA nanoparticles for efficient gene delivery to lung cancer cells. The bioadhesive agent and stabilizer, Carbopol 940 was chosen to establish bioadhesive PLGA nanoparticles and Pluronic F68, Pluronic F127 stabilized PLGA nanoparticles were formulated as control. The effects of different surfactants on the physicochemical and biological characterizations of PLGA nanoparticles were compared. All the obtained nanoparticles showed negative surface charge, similar spherical morphology, a relatively narrow particle size distribution, and lower cytotoxicity to A549 cells comparing with Lipofectamine 2000. Carbopol stabilized nanoparticles hold advantages in DNA-binding efficiency (>80%) at an optimal Carbopol concentration, DNA protection from enzymatic degradation in vitro release and better buffering capacity. Most importantly, higher transfection efficiency in A549 cells was observed comparing to Pluronics stabilized nanoparticles or naked DNA, similar to that of Lipofectamine 2000. These results revealed that the bioadhesive PLGA nanoparticles formulated with Carbopol might be a very attractive candidate as a non-viral vector for lung cancer gene therapy and might alleviate the drawbacks of the conventional cationic vectors/DNA complexes for gene delivery in vivo.
Keywords: Bioadhesive nanoparticles; PLGA; Gene delivery; Carbopol (CP); Lung cancer;
Particle size control of poly(dl-lactide-co-glycolide) nanospheres for sterile applications by Yusuke Tsukada; Kaori Hara; Yohei Bando; C.C. Huang; Yasuo Kousaka; Yoshiaki Kawashima; Ryuichi Morishita; Hiroyuki Tsujimoto (196-201).
After optimization, PLGA nanospheres with a mean particle size of 102–163 nm and the 100–98% of filtration fraction could be produced and passed the bacteria challenge tests. This study found PLGA nanospheres can be efficiently prepared as a sterile product.
Keywords: PLGA nanospheres; ESD method; Drug delivery system; Pressure filtration; Sterilization; Particle size;
Development of an oral rutin nanocrystal formulation by Rachmat Mauludin; Rainer H. Müller; Cornelia M. Keck (202-209).
Dried rutin nanocrystals have been prepared by lyophilization and investigated regarding their physicochemical properties with respect to re-dispersability, particle size, morphology and dissolution behavior. Photon correlation spectroscopy (PCS) and laser diffractometry (LD) were employed to determine the particle size. Morphology of the particles was analyzed by light microscopy. Lyophilized rutin nanocrystals were incorporated into tablets and the dissolution behavior of the tablets was evaluated. Very fine particles of lyophilized rutin could be completely re-dispersed in the water. The PCS size average and polydispersity index (PI) of lyophilized rutin were of 721 nm and of 0.288 after re-dispersion. The rutin nanocrystal-loaded tablets were produced using direct compression. The dissolution velocity of the rutin nanocrystal-loaded tablet was superior compared to rutin microcrystal-loaded and a marketed tablet. After 30 min rutin was released and dissolved completely from the nanocrystal tablets in water. In contrast, only 71% and 55% of the total amount of rutin were dissolved from the microcrystal tablets and the marketed tablet, respectively. The improving dissolution behavior of the rutin nanocrystal-loaded tablet should lead to a better bioavailability of the poorly soluble rutin in the body.
Keywords: Nanocrystals; Rutin; Lyophilization; Re-dispersion; Rutin nanocrystal-loaded tablet; Dissolution behavior;
Preparation, pharmacokinetics and tissue distribution of micelles made of reverse thermo-responsive polymers by Xingguo Yang; Lingbing Li; Yuexia Wang; Yebang Tan (210-215).
New reverse thermo-responsive polymers, poly(ethylene oxide)–poly(propylene oxide) multiblock copolymers (poly(ether-carbonate)s) were synthesized. The micelles made of new reverse thermo-responsive polymers were also prepared loaded with the poorly soluble anticancer drug, hydroxycamptothecin (HCPT). The structure characterization of poly(ether-carbonate)s was determined by 1H NMR and FT-IR analysis. The critical micelle concentration (CMC), critical micelle temperature (CMT), size distribution and drug release in vitro were determined. The pharmacokinetics and tissue distribution in vivo for novel copolymer micelles were studied. The experimental results showed that the micelles was spherical in appearance and dispersed well. The process of HCPT release from micelles in vitro was composed of two steps, abrupt release and sustained release. After i.v. administration (2 h), the drug concentration of poly(ether-carbonate) micelles group in liver in mice was 3.46 μg/g, while that of HCPT injection group was 0.401 μg/g. Compared with HCPT injection, the elimination half-life of poly(ether-carbonate) micelles group was prolonged remarkably from 1.3 to 12.5 h. The poly(ether-carbonate) micelles showed a combination of liver targeting and sustained drug release in experiments on animals.
Keywords: Reverse thermo-responsive polymers; Micelles; Hydroxycamptothecin; Pharmacokinetics; Tissue distribution;
Characterization of the inhibition of breast cancer resistance protein-mediated efflux of mitoxantrone by pharmaceutical excipients by Tetsuo Yamagata; Mariko Morishita; Hiroyuki Kusuhara; Kozo Takayama; Hassan Benameur; Yuichi Sugiyama (216-219).
Previously we showed that some excipients can inhibit breast cancer resistance protein (BCRP/ABCG2) in vitro and in vivo. We then evaluated the reversibility and the mode of BCRP inhibition of excipients, such as Tween 20 and Pluronic P85, by the intracellular mitoxantrone uptake study. To evaluate the reversibility of BCRP inhibitory effects, BCRP expressing cells were preincubated with the excipients and the intracellular mitoxantrone uptake was determined after removing or not removing the excipients. To evaluate the mode of BCRP inhibitory effects, the intracellular mitoxantrone uptake at the different mitoxantrone concentrations in the medium with the excipients was determined. Both Tween 20 and Pluronic P85 increased the mitoxantrone uptake in BCRP expressing cells, but these effects were disappeared when the excipients were removed. Moreover, both excipients increased the uptake at low substrate concentrations. However, at high substrate concentrations, Tween 20 increased the uptake to less extent compared with low substrate concentrations, whereas there was no such effect of Pluronic P85. Taken together, Pluronic P85 and Tween 20 appear to inhibit BCRP-mediated efflux of mitoxantrone reversibly and the inhibition mode of Pluronic P85 may be competitive but not that of Tween 20, which may be mixed type.
Keywords: BCRP; Excipients; Inhibition; Reversible; Competitive or noncompetitive;