Polymeric Micelles Based on Modified Glycol Chitosan for Paclitaxel Delivery: Preparation, Characterization and Evaluation.

Amphiphilic polymer of α-tocopherol succinate modified glycol chitosan (TS-GC) was successfully constructed by conjugating α-tocopherol succinate to the skeleton of glycol chitosan and characterized by Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (¹H-NMR). In aqueous milieu, the conjugates self-assembled to micelles with the critical aggregation concentration of 7.2 × 10−3 mg/mL. Transmission electron microscope (TEM) observation and dynamic light scattering (DLS) measurements were carried out to determine the physicochemical properties of the micelles. The results revealed that paclitaxel (PTX)-loaded TS-GC micelles were spherical in shape. Moreover, the PTX-loaded micelles showed increased particle sizes (35 nm vs. 142 nm) and a little reduced zeta potential (+19 mV vs. +16 mV) compared with blank micelles. The X-ray diffraction (XRD) spectra demonstrated that PTX existed inside the micelles in amorphous or molecular state. In vitro and in vivo tests showed that the PTX-loaded TS-GC micelles had advantages over the Cremophor EL-based formulation in terms of low toxicity level and increased dose, which suggested the potential of the polymer as carriers for PTX to improve their delivery properties.

A pre-formulation study of a polymeric solid dispersion of paclitaxel prepared using a quasi-emulsion solvent diffusion method to improve the oral bioavailability in rats.

OBJECTIVE: To preliminarily develop a surfactant-free, polymeric solid dispersion (PSD) of paclitaxel suitable for oral administration. METHODS: A co-solvent quench method was applied to screen the proper polymer matrix of the PSD which were prepared in a liquid system using a quasi-emulsion solvent diffusion method (QESDM). Three dissolution experiments and two in vivo tests in rats were used to explain the differences among the formulations. RESULTS: The theoretical solubility ratio of amorphous/crystalline PTX was 92.6 (37 °C). Hydroxypropyl methylcellulose acetate succinate (HPMCAS) was chosen as the polymer carrier of the PSD and a porous silicon dioxide [called white carbon black (WCB)] was selectable to be used to further adjust the dissolution rate. The absolute oral bioavailability (AOB, 20 mg/kg) of the three formulas [HPMCAS/paclitaxel/WCB = 4/1/0 (F1), 8/1/0 (F2) and 4/1/4 (F3), w/w/w] were 11.8, 13.6 and 25.6%, respectively. The AOB of F3 is nearly seven times higher than that (3.8%) of paclitaxel material (a control). The advantage of higher HPMCAS/paclitaxel ratio of F2 in a dissolution test was not reflected in the first in vivo test due to the relatively higher dose of polymer which could not be effectively dissolved under the limitation of intestinal environment. This was deduced from the dissolution tests and was finally validated when the oral dose of PTX (and thus polymer) was reduced. The relevant AOBs (10 mg/kg) were 10.4, 20.8 and 19.6%, respectively. CONCLUSION: The PSD is a promising formulation strategy and the QESDM is a practical preparation method to implement such formulation design.

Multifunctional Composite Microcapsules for Oral Delivery of Insulin.

In this study, we designed and developed a new drug delivery system of multifunctional composite microcapsules for oral administration of insulin. Firstly, in order to enhance the encapsulation efficiency, insulin was complexed with functional sodium deoxycholate to form insulin-sodium deoxycholate complex using hydrophobic ion pairing method. Then the complex was encapsulated into poly(lactide-co-glycolide) (PLGA) nanoparticles by emulsion solvent diffusion method. The PLGA nanoparticles have a mean size of 168 nm and a zeta potential of -29.2 mV. The encapsulation efficiency was increased to 94.2% for the complex. In order to deliver insulin to specific gastrointestinal regions and reduce the burst release of insulin from PLGA nanoparticles, hence enhancing the bioavailability of insulin, enteric targeting multifunctional composite microcapsules were further prepared by encapsulating PLGA nanoparticles into pH-sensitive hydroxypropyl methyl cellulose phthalate (HP55) using organic spray-drying method. A pH-dependent insulin release profile was observed for this drug delivery system in vitro. All these strategies help to enhance the encapsulation efficiency, control the drug release, and protect insulin from degradation. In diabetic fasted rats, administration of the composite microcapsules produced a great enhancement in the relative bioavailability, which illustrated that this formulation was an effective candidate for oral insulin delivery.

Development of an osmotically-driven pellet coated with acrylic copolymers (Eudragit® RS 30 D) for the sustained release of oxymatrine, a freely water soluble drug used to treat stress ulcers (I): in vitro and in vivo evaluation in rabbits.

PURPOSE: To develop an osmotically-driven pellet coated with polymeric film for sustained release of oxymatrine (OMT), a freely water soluble drug. METHODS: Pellet containing OMT and sodium chloride (NaCl), an osmotically active agent, were prepared by extrusion/spheronization and then coated with acrylic copolymers (Eudragit(®) RS 30 D) by the fluidized bed coating process. In vitro release and swelling behavior studies were employed to optimize and to evaluate the sustained-release behavior from the osmotically-driven pellets with film coated. Finally, in vivo evaluation in rabbits was employed to investigate the sustained plasma level of OMT and its active metabolite matrine. RESULTS: It was found that the F3 formulation, prepared with 20% NaCl and an 8% coating level, showed a continuous NaCl-induced water influx into the pellets providing a gradual sustained release of OMT for over 12 h. Finally, we confirmed that oral OMT with sustained release led to a gradual sustained plasma profile of both OMT, with a reduction in its bioavailability, and MT with an increase in the bioavailability compared with that of oral OMT with immediate release. CONCLUSIONS: The pharmaceutical parameters obtained suggested the potential usefulness of oral OMT with sustained release for the treatment of stress ulcers, as well as reducing the risk of MT-induced side effects.

Polymer-mediated anti-solvent crystallization of nitrendipine: monodispersed spherical crystals and growth mechanism.

PURPOSE: To investigate anti-solvent crystallization and growth mechanism of nitrendipine spherical crystals in an aqueous solution containing polymeric additives. METHODS: Size and shape of crystals were investigated using laser diffractometry, optical microscopy and scanning electron microscopy (SEM). Crystalline form was determined by X-ray powder diffractometer (XRPD). During crystal growth, morphological changes at different time points were observed using SEM. RESULTS: Morphology of nitrendipine crystals was affected by polymers and temperature. Monodispersed micro-spherical crystals were obtained when polyvinyl alcohol (PVA) and PEG 200 were present in crystallization medium at 2°C. During crystallization, large number of amorphous nanoparticles was first observed, followed by aggregation into a core for spherical crystals. Once crystalline state was achieved, rapid growth on core surface was observed with amorphous particles acting as a reservoir allowing formation of star-like particles with needle-like subunits. Spherical crystals were formed by filling the gap between needle-like distinct crystalline units of star-like templates with molecules from dissolved amorphous particles. CONCLUSIONS: Monodispersed nitrendipine spherical crystals were obtained using carefully controlled conditions. A mechanism for the nitrendipine spherical crystal growth is suggested. These findings provide a new insight into spherulitic crystallization of active pharmaceutical ingredients.

Investigation of a new injectable thermosensitive hydrogel loading solid lipid nanoparticles.

For improving the effectiveness of cancer chemotherapy and avoiding rapid clearance of solid lipid nonoparticles (SLN) from the systemic circulation following systemic administration, 2-methoxyestradiol (2-ME) as model drug, PLGA-PEG-PLGA as hydrogel material, an injectable SLN loaded hydrogel was developed. Integrity of SLN within and released from the hydrogel was confirmed by direct visualization by a scanning electron microscope (SEM), particle size measurement by laser light scattering, and free drug concentration in the release medium by ultracentrifugation. Moreover, in vitro release, thermo-sensitive properties and rheological behavior were investigated. The results indicated that SLN were stable in the hydrogel. In the release medium, most 2-ME existed in the SLN and intact 2-ME SLN could be released from the hydrogel for a prolonged period over 46 days. Their concentration showed a significant effect on the release rate, in contrast to particle size and pH value of the release medium. In addition, the SLN loaded hydrogel could still exhibit reversible thermo-sensitive properties and better syringeability. These results suggested that the SLN loaded hydrogel could transport SLN to the target site and control prolonged release of SLN, which may increase the efficacy of cancer chemotherapy.

Nitrendipine nanocrystals: its preparation, characterization, and in vitro-in vivo evaluation.

The present investigation was undertaken with the objective of developing a solid formulation containing nitrendipine nanocrystals for oral delivery. Nitrendipine nanocrystals were prepared using a tandem precipitation-homogenization process. Then, spray drying, a cost-effective method very popular in industrial situations, was employed to convert the nanocrystals into a solid form. The parameters of the preparation process were investigated and optimized. The optimal process was as follows: firstly, nitrendipine/acetone solution (100 mg/ml) was added to a polyvinyl alcohol solution (1 mg/ml) at 10°C, then the pre-suspension was homogenized for 20 cycles at 1,000 bar. Both differential scanning calorimetry and X-ray diffraction analysis indicated that nitrendipine was present in crystalline form. The in vitro dissolution rate of the nanocrystals was significantly increased compared with the physical mixture and commercial tablet. The in vivo testing demonstrated that the C(max) of the nanocrystals was approximately 15-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively. In addition, the AUC(0→24) of the nanocrystals was approximately 41-fold and 10-fold greater than that of physical mixture and commercial tablet, respectively.

Insulin-S.O (sodium oleate) complex-loaded PLGA nanoparticles: formulation, characterization and in vivo evaluation.

S.O (sodium oleate) is an anionic surfactant, which is able to forman ionic complex with positively charged insulin at suitable pH. In a previous study, the insulin-S.O (Ins-S.O) complex was prepared by a hydrophobic ion pairing (HIP) method to improve the apparent liposolubility of insulin. The formation of the complex was further confirmed by Zeta potential and X-ray method. Based on the preliminary study, poly(lactide-co-glycolide) (PLGA) nanoparticles harbouring Ins-S.O complex was prepared via an emulsion solvent diffusion method. The effects of key parameters such as concentration of PVA, concentration of PLGA and initial-loaded drug on the properties of the nanoparticles were investigated. The insulin encapsulation efficiency (EE(%)) reached up to 91.2% and mean diameter of the nanoparticles was sized approximately 160 nm under optimal conditions. The pharmacological effects of the nanoparticles made of PLGA (75/25, Av Mw 15,000) were further evaluated to confirm their potential suitability for oral delivery. In order to evaluate hyperglycaemic effect of the nanoparticles for oral administration, Ins-S.O complex-loaded PLGA nanoparticles (20 IU/Kg) were administered orally by force-feeding to diabetic rats. In the case of the nanoparticles, the plasma glucose level reduced to 23.85% from the initial one 12 h post-administration and this continued for 24 h. The results showed that the use of Ins-S.O complex-loaded PLGA nanoparticles is an effective method of reducing plasma glucose levels. The insulin nanoparticles also improved the glycaemic response to an oral glucose challenge.

Modified hydrolysis kinetics of the active lactone moiety of 10-hydroxycamptothecin by liposomal encapsulation.

The key structural requirement for the antitumor activity of 10-hydroxycamptothecin (HCPT) is the intact lactone moiety which is always instability and suffered from pH-dependent hydrolysis. The aim of this study was to evaluate the protection effects of liposomal encapsulation on the labile lactone ring. Mono-modal dispersed quasi-spherical liposomes with mean diameter of 145 nm and high drug entrapment efficiency of 90% were obtained under optimal conditions. The in vitro hydrolysis kinetics behaviors of lactone were studied in varied pH buffers. Compared to that of free HCPT in solution formulation, both the hydrolysis half-life and observed equilibrium constant of liposomal HCPT were increased significantly along with the decreased apparent hydrolysis rate constant. The plasma pharmacokinetics was studied by assessing the lactone stability versus time profiles in vivo following intravenous administration of free and liposomal HCPT. The liposomal encapsulation led to a twofold increase in the AUC values and significant decrease in the plasma clearance of lactone (P < 0.05). There was a good correlation between in vitro and in vivo stability of HCPT-lactone. These results suggested a potential application of the novel liposome formulation for the stable delivery system of HCPT.

Design of high payload PLGA nanoparticles containing melittin/sodium dodecyl sulfate complex by the hydrophobic ion-pairing technique.

The water-soluble peptide, melittin, was modified with an anionic agent, sodium dodecyl sulfate by hydrophobic ion-pairing. Investigations showed that the formed complex was very soluble in organic solvent, especially, in dimethylsulfoxide and dehydrated alcohol. Furthermore, the physiochemical properties of the complex in the solid state or in an aqueous medium were characterized using octanol/water partition measurement, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The complex was formulated into poly(D,L-lactide-co-glycolide acid) nanoparticles by an emulsion solvent diffusion method. It was found that the nanoparticles of about 130 nm in size can be produced with a high encapsulation efficiency, and the entrapment of nanoparticles prepared with the formed complex increased from about 50% to nearly 100% compared with that for pure melittin. Moreover, the growth inhibitory effects of modified melittin and melittin-loaded nanoparticles in breast cancer MCF-7 cells were not changed comparing with free melittin as determined by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay.

Optimized formulation of high-payload PLGA nanoparticles containing insulin-lauryl sulfate complex.

A novel poly(lactic acid-co-glycolic acid) nanoparticle loaded with insulin-lauryl sulfate complex was prepared by spontaneous emulsion solvent diffusion method. The effects of key parameters such as agitation speed, poly(vinyl alcohol) concentration, solvent composition, polymer concentration, and the volume of external aqueous phase on the properties of the nanoparticles were investigated. To enhance the drug recovery and drug content simultaneously, a response surface methodology with five-level, two-factor central composite design was employed. The weight ratio of polymer to drug and volume ratio of external aqueous phase to solvent phase were selected as controlled factors on account of their interactions found in the monofactorial investigations. The experimental datum allowed the development of quadratic models (p < .05) describing the inter-relationships between the dependent and independent variables. By solving the regression equation, and graphic analyzing the response surface contour and plots, the optimum values of the two factors were determined as 20/1 and 10/1. The optimized conditions led to 89.6% of drug recovery and 4.57% of drug content during nanoparticle preparation.

Studies on PEG-modified SLNs loading vinorelbine bitartrate (I): preparation and evaluation in vitro.

In this study, the conjugate of PEG2000-stearic acid (PEG2000-SA) was used to prepare PEGylated solid lipid nanoparticles loading vinorelbine bitartrate (VB-pSLNs) by cold homogenization technique. The particle size and zeta potential of resulted VB-pSLNs ranged 180-250nm and 0-10mV, which were determined using a Zetasizer, respectively. Although the drug entrapment efficiency (EE) slightly decreased after the PEG modification of VB-SLNs, above 60 % EE could be reached. The drug release tests in vitro indicated the faster drug release from VB-pSLNs than that from VB-SLNs without PEG modification. To investigate the cellular uptake of VB-pSLNs, the chemical conjugate of octadecylamine-fluorescein isothiocynate (FITC-ODA) was synthesized, and was used as a fluorescence marker to incorporate into nanoparticles. The results from cellular uptake indicated that the phagocytosis of VB-pSLNs by RAW264.7 cells was inhibited effectively by the PEG modification of SLNs, while the uptake by cancer cells (MCF-7 and A549) could be improved significantly. The assay of anticancer activity in vitro demonstrated that the anticancer activity of VB was significantly enhanced by the encapsulation of SLNs and pSLNs due to the increased cellular internalization of drug. The results suggested that SLNs and pSLNs could be excellent carrier candidates to entrap VB for tumor chemotherapeutics.

Preparation of insulin loaded PLGA-Hp55 nanoparticles for oral delivery.

The aim of the present work was to investigate the preparation of PLGA nanoparticles (PNP) and PLGA-Hp55 nanoparticles (PHNP) as potential drug carriers for oral insulin delivery. The nanoparticles were prepared by a modified emulsion solvent diffusion method in water, and their physicochemical characteristics, drug release in vitro and hypoglycemic effects in diabetic rats were evaluated. The particle sizes of the PNP and PHNP were 150+/-17 and 169+/-16 nm, respectively, and the drug recoveries of the nanoparticles were 50.30+/-3.1 and 65.41+/-2.3%, respectively. The initial release of insulin from the nanoparticles in simulated gastric fluid over 1 h was 50.46+/-6.31 and 19.77+/-3.15%, respectively. The relative bioavailability of PNP and PHNP compared with subcutaneous (s.c.) injection (1 IU/kg) in diabetic rats was 3.68+/-0.29 and 6.27+/-0.42%, respectively. The results show that the use of insulin-loaded PHNP is an effective method of reducing serum glucose levels.

Preparation of an enteric-soluble solid-state emulsion using oily drugs.

To improve the patient's compliance and enhance the stability of oily drugs in the gastric fluid, an enteric-soluble solid-state emulsion (ESE), was developed. The ESE was prepared by spreading liquid o/w-emulsions on a flat glass and drying at the oven maintained at 40 degrees C. Aerosil 200 was applied as solid carrier and emulsifier. And Eudragit L30D-55 was used as enteric coating material. The influence of various preparation parameters on the residual volatile oil and the release behavior was investigated. Droplet size distribution of the primary emulsions and the emulsion after reconstitution of zedoary turmeric oil (ZTO) ESE in the phosphate buffer were also measured. When ZTO ESE was immersed into phosphate buffer (pH 6.8), the stable emulsion was formed in 20min, but the release was obviously suppressed when it was exposed to the gastric fluid. It was concluded that preparation of enteric-soluble solid-state emulsion by the present method for oral oily drug was feasible.

Enhanced immune responses induced by vaccine using Sendai virosomes as carrier.

Sendai virosomes can deliver encapsulated contents into the cytoplasm directly in a virus fusion-dependent manner. In this paper, Sendai virosomes-formulated melanoma vaccine was constructed and its anti-tumor effects were investigated. The melanoma vaccine was prepared by encapsulating mixture antigen into the Sendai virosomes. The antigen, mixture proteins were extracted from B(16) melanoma cells. The cytotoxic T lymphocyte (CTL) response level was evaluated by (51)Cr release method, and the change of CD4(+) and CD8(+) expression as well as the concentration of IgG in serum of immunized mice was measured. The results showed that Sendai virosomes-formulated melanoma vaccine can effectively elicit not only systemic immune response but also strong CTL response. Sendai virosomes can be used as an effective vector for use in anti-tumor vaccine therapy.

Enhanced solubility and stability of PEGylated liposomal paclitaxel: in vitro and in vivo evaluation.

An improved PEGylated liposomal formulation of paclitaxel has been developed with the purpose of improving the solubility of paclitaxel as well as the physicochemical stability of liposome in comparison to the current Taxol formulation. The use of 3% (v/v) Tween 80 in the hydration media was able to increase the solubility of drug. The addition of sucrose as a lyoprotectant in the freeze-drying process increased the stability of the liposome particles. There was no significant difference in the entrapment efficiency of paclitaxel between the conventional non-PEGylated liposomes and our PEGylated liposomes. Cytotoxicity in human breast cancer cell lines (MDA-MB-231 and SK-BR-3) of our paclitaxel formulation was less potent compared to Taxol after 24h incubation, but was equipotent after 72 h due to the slower release of drug from the liposome. Our PEGylated liposomes increased the biological half-life of paclitaxel from 5.05 (+/-1.52)h to 17.8 (+/-2.35)h compared to the conventional liposomes in rats. Biodistribution studies in breast cancer xenografted nude mouse model showed that our liposomes significantly decreased the uptake in reticuloendothelial system (RES)-containing organs (liver, spleen and lung) while increasing the uptake in tumor tissues after injection compared to Taxol or the conventional liposomal formulation. Moreover, the PEGylated liposome showed greater tumor growth inhibition effect in in vivo studies. Therefore, our PEGylated liposomal formulation of paclitaxel could serve as a better alternative for the passive targeting of human breast tumors.

Liposome formulation of paclitaxel with enhanced solubility and stability.

Despite its strong antitumor activity, paclitaxel (Taxol) has limited clinical applications due to its low aqueous solubility and hypersensitivity caused by Cremophor EL and ethanol which is the vehicle used in the current commercial product. In an attempt to develop a pharmaceutically acceptable formulation that could replace Taxol, a paclitaxel incorporated liposome has been constructed to improve solubility and physicochemical stability. The effect of various components of the liposome, including cholesterol and lipid, on the solubility and entrapment efficiency (EE) of paclitaxel was systematically investigated. The results showed that 5% (v/v) of polyethylene glycol 400 in the hydration medium of liposome significantly increased the solubility (up to 3.39 mg/mL) as well as the EE and the paclitaxel content in the liposome formulation composed of 10% (w/v) of S(100)PC with cholesterol (cholesterol-to-lipid molar ratio = 10:90). When sucrose (sugar-to-lipid molar ratio = 2.3) was added as a lyoprotectant during the freeze-drying of the liposome, physicochemical stability of liposome was significantly improved. Moreover, the cytotoxicity of the final liposome formulation against MDA-MB-231 human breast cancer cell line was not significantly different from that of Taxol. The enhanced aqueous solubility as well as the physicochemical stability of paclitaxel in the liposome formulation developed in this study could be a safer and effective alternative to the Cremophor EL and ethanol formulation.

Biodegradable nanoparticles loaded with insulin-phospholipid complex for oral delivery: preparation, in vitro characterization and in vivo evaluation.

Biodegradable nanoparticles loaded with insulin-phospholipid complex were prepared by a novel reverse micelle-solvent evaporation method, in which soybean phosphatidylcholine (SPC) was employed to improve the liposolubility of insulin, and biodegradable polymers as carrier materials to control drug release. Solubilization study, IR and X-ray diffraction analysis were employed to prove the complex formation. The effects of key parameters such as polymer/SPC weight ratio, organic phase and polymer type on the properties of the nanoparticles were investigated. Spherical particles of 200 nm mean diameter and a narrow size distribution were obtained under optimal conditions. The drug entrapment efficiency was up to 90%. The in vitro drug release was characterized by an initial burst and subsequent delayed release in both pH 6.8 and pH 1.2 dissolution mediums. The specific modality of drug release, i.e., free or SPC-combined, was investigated in the aid of ultracentrifugation and ultrafiltration methods. The influence of polymer type on the drug release was also discussed. The pharmacological effects of the nanoparticles made of PLGA 50/50 (Av.Mw 9500) were further evaluated to confirm their potential suitability for oral delivery. Intragastric administration of the 20 IU/kg nanoparticles reduced fasting plasma glucose levels to 57.4% within the first 8 h of administration and this continued for 12 h. PK/PD analysis indicated that 7.7% of oral bioavailability relative to subcutaneous injection was obtained.

Short-term delayed-release microcapsules spraycoated with acrylic terpolymers.

A series of poly(ethyl acrylate (EA)/methyl methacrylate (MMA)/2-hydroxyethyl methacrylate (HEMA)) lattices were synthesized to prepare short-term delayed-release microcapsules by employing the Wurster coating process. Latex with a HEMA molar fraction exceeding 60% could not be synthesized as an aqueous suspension due to latex particle precipitation. The effects of monomer composition on the particle size of latex and the water-uptake and glass transition temperature (T(g)) of cast films were investigated. Lattices whose T(g) ranged from 40 to 80 degrees C were used to prepare the microcapsules. Most of the lattices exhibited excellent process performance while coating particles that were smaller than 100 microm: the product yields were 85.1-90.6% and the mean particle sizes were 82-85 microm. However, since the lattices with high molar ratios of EA and HEMA were highly hydrophilic and strongly adhesive, the core particles in the coating were severely agglomerated. The microcapsules coated with lattices whose HEMA molar fractions were higher than 50% were unable to retard the release of carbazochrome sodium sulfonate, a water-soluble model drug, during the initial 0.5 min. Poly(EA/MMA/HEMA) with a molar ratio of 9:9:10 appeared to be suitable for the preparation of short-term delayed-release microcapsules by the Wurster coating process.

Preparation of roxithromycin-polymeric microspheres by the emulsion solvent diffusion method for taste masking.

Microspheres of roxithromycin with Eudragit S100 and silica were prepared by the emulsion solvent diffusion method to mask the bitter taste of the antibiotic. The effect of different polymers and drug-polymer ratios on the taste masking and the characteristics of the microspheres were investigated. It was found that Eudragit S100 was the best for masking the unpleasant taste of roxithromycin among the six kinds of polymers investigated. The results of DSC, X-ray diffraction and IR showed that there were several combinations of roxithromycin and Eudragit S100. The influence of other formulation factors, i.e. dichloromethane-acetone ratios and silica-polymer ratios on the properties of the microspheres were also examined. In conclusion, the results of the present study will be helpful for the preparation of oral forms of roxithromycin with an acceptable taste.