Selective adherence of a sucralfate-tetracycline complex to gastric ulcers: implications for the treatment of Helicobacter pylori

To control floating drug delivery system in a simulated gastric environment by adjusting the Shell layer formulation

Background

Gastroretentive drug delivery system (GDDS) are novel systems that have been recently developed for treating stomach diseases. The key function of all GDDS systems is to control the retention time in the stomach. However, research into the bulk density or entanglement of polymers, especially regarding their effects on drug float and release times, is scarce.

Methods

In this research, we prepared the floating core-shell beads carrying tetracycline. The ratio of chitosan and xanthan gum in the shell layer was changed to modify polymer compactness. Tetracycline was encapsulated in the alginate core.

Results

Using scanning electron microscopy (SEM) techniques, we observed that the shell formulation did not change the bead morphology. The cross-sectional images showed that the beads were highly porous. The interaction between anionic xanthan gum and cationic chitosan made the shell layer dense, resisting to the mass transfer in the shell layer. Due to the high mass transfer resistance to water penetration, the longer float and delivery time were caused by the dense surface of the beads. The cell culture demonstrated that floating core-shell beads were biocompatible. Importantly, the beads with tetracycline showed a significant prolonged anti-bacterial effect.

Conclusion

Research results proved that the floating and releasing progress of core-shell beads can be well controlled by adjusting the shell layer formulation that could promote the function of gastroretentive drugs.

Floating microspheres bearing acetohydroxamic acid for the treatment of Helicobacter pylori

This investigation is part of our ongoing effort to develop effective drug delivery systems for the treatment of Helicobacter pylori infection using polycarbonate (PC) floating microspheres as drug carriers. In an effort to augment the anti-H. pylori effect of acetohydroxamic acid (AHA), floating PC microspheres, which have the ability to reside in the gastrointestinal (GI) tract for an extended period, were prepared by emulsion (O/W) solvent evaporation technique. The effect of PC concentration on the morphology, particle size, entrapment efficiency and drug release rate was studied. In-vitro studies confirmed the excellent floating properties of PC microspheres. In-vitro and in-vivo growth inhibition studies were performed on developed system(s) taking isolated cultures of H. pylori and H. pylori-infected Mongolian gerbils, respectively. The drug and PC microspheres both showed anti-H. pylori activity in vivo, but the required dose of AHA was effectively reduced by a factor of 10 in the case of PC microspheres. In conclusion, the floating microspheres more effectively cleared H. pylori from the GI tract than the drug because of the prolonged gastric residence time resulting from the excellent buoyancy of the PC.

Polyelectrolyte coated multilayered liposomes (nanocapsules) for the treatment of Helicobacter pylori infection

Helicobacter pylori infection is one of the major causes of gastric cancers. A number of systems have already been reported, but 100% eradication has never been achieved. The present invention designs a gastro-retentive drug delivery system incorporated with amoxicillin and metronidazole, specifically suited for the eradication of Helicobacter pylori infections due to its mucoadhesiveness in the presence of polyelectrolyte polymers. The system possesses the advantages of both vesicular and particulate carriers, and it was prepared by alternative coating of polyanion (poly(acrylic acid), PAA) and polycation (poly(allylamine hydrochloride), PAH) using liposomes as the core. Compared with the conventional liposomes, the polyelectrolyte based multilayered system (nanocapsules) gave prolonged drug release in simulated gastric fluid, which is well suited for drug delivery against H. pylori infection in the stomach. In vitro growth inhibition study, agglutination assay, and in situ adherence assay in cultured H. pylori suggested the successful in vitro activity and binding propensity of the system. In vivo bacterial clearance study carried out in a H. pylori infected mouse model finally confirmed the success of the developed novel nanocapsule system. Thus, the newly developed composite nanocapsules along with the use of combination therapy proved to have commendable potential in Helicobacter pylori eradication as compared to already existing conventional and novel drug delivery systems.

Formulation and evaluation of clarithromycin microspheres for eradication of Helicobacter pylori

The objective of the study was to develop a stomach-specific drug delivery system for controlled release of clarithromycin for eradication of Helicobacter pylori (H. pylori). Floating-bioadhesive microspheres of clarithromycin (FBMC) were prepared by emulsification-solvent evaporation method using ethylcellulose as matrix polymer and Carbopol 934P as mucoadhesive polymer. The prepared microspheres were subjected to evaluation for particle size, incorporation efficiency, in vitro buoyancy, in vitro mucoadhesion and in vitro drug release characteristics. The prepared microspheres showed a strong mucoadhesive property with good buoyancy. The formulation variables like polymer concentration and drug concentration influenced the in vitro drug release significantly in simulated gastric fluid (pH. 2.0). The in vivo H. pylori clearance efficiency of prepared FBMC in reference to clarithromycin suspension following repeated oral administration to H. pylori infected Mongolian gerbils was examined by polymerase chain reaction (PCR) technique and by a microbial culture method. The FBMC showed a significant anti-H. pylori effect in the in vivo gerbil model. It was also noted that the required amount of clarithromycin for eradication of H. pylori was significantly less in FBMC than from corresponding clarithromycin suspension. The results further substantiated that FBMC improved the gastric stability of clarithromycin (due to entrapment within the microsphere) and eradicated H. pylori from the gastrointestinal tract more effectively than clarithromycin suspension because of the prolonged gastrointestinal residence time of the formulation.

Development and evaluation of a novel floating in situ gelling system of amoxicillin for eradication of Helicobacter pylori

The aim of this study was to develop a new intra-gastric floating in situ gelling system for controlled delivery of amoxicillin for the treatment of peptic ulcer disease caused by Helicobacter pylori (H. pylori). Gellan based amoxicillin floating in situ gelling systems (AFIG) were prepared by dissolving varying concentrations of gellan gum in deionized water containing sodium citrate, to which varying concentrations of drug and calcium carbonate, as gas-forming agent, was added and dissolved by stirring. The formulation variables like concentration of gellan gum and calcium carbonate significantly affected the in vitro drug release from the prepared AFIG. The in vivo H. pylori clearance efficacy of prepared AFIG in reference to amoxicillin suspension following repeated oral administration to H. pylori infected Mongolian gerbils was examined by polymerase chain reaction (PCR) technique and by a microbial culture method. AFIG showed a significant anti-H. pylori effect in the in vivo gerbil model. It was noted that the required amount of amoxicillin for eradication of H. pylori was 10 times less in AFIG than from the corresponding amoxicillin suspension. The results further substantiated that the prepared AFIG has feasibility of forming rigid gels in the gastric environment and eradicated H. pylori from the gastrointestinal tract more effectively than amoxicillin suspension because of the prolonged gastrointestinal residence time of the formulation.

Clinical trial evaluating amoxicillin and clarithromycin hydrogels (Chitosan-polyacrylic acid polyionic complex) for H. pylori eradication

AIM

It has been suggested that enhancement of amoxicillin or clarithromycin concentration at the gastric tissue may improve the anti-Helicobacter pylori effect of these drugs. This could be achieved by allowing the drug to remain longer in the stomach using dried hydrogels. Our aim was to evaluate the efficacy of an H. pylori eradication regimen including both amoxicillin and clarithromycin hydrogels.

DESIGN

prospective clinical trial.

PATIENTS

with peptic ulcer or functional dyspepsia.

INTERVENTION

7-day rabeprazole-amoxicillin-clarithromycin regimen. In addition, amoxicillin and clarithromycin hydrogels were administered twice daily during the 7 days. The polyionic complex hydrogel was prepared with Chitosan and polyacrylic acid.

OUTCOME

H. pylori eradication was defined as a negative C-urea breath test 8 weeks after completing therapy.

RESULTS

Forty patients were included. One patient did not return for follow-up. Ninety percent of the patients took all the medications correctly. Per-protocol and intention-to-treat eradication rates were 74% (95% CI=58%-86%) and 70% (55%-82%). Mild adverse effects were reported in 4 (10%) patients (diarrhea in 3, and nausea/heartburn in 1).

CONCLUSIONS

Although dried polyionic complexes could serve as suitable candidates for amoxicillin and clarithromycin site-specific delivery in the stomach, its addition does not increase the eradication efficacy of the generally prescribed proton pump inhibitor plus amoxicillin and clarithromycin regimen.

The acidic complexation of tetracycline with sucralfate for its mucoadhesive preparation

The complex of antibiotics with sucralfate (SF) was prepared with acid. The mechanism of the complexation and some factors concerning the preparation, which influence the mucoadhering property, were studied. The complexation was confirmed by the change in color and instrumental analysis. The acidic complex appeared to be produced by reagglomeration of SF preliminary particles. It was suggested that the amide or amine groups of tetracycline (TC) and aluminum moieties of SF serve as the binding sites. The potential of multiple binding sites and a priority in them were suggested by the Scatchard plot analysis. The additional amounts of acid and the increase in the surface area increased the number of sites. The amount of the additional acid appeared to be the most important factor during the preparation of the acidic complex. The appropriate amount of acid added appeared to produce a complex rich in TC. However, an excess amount might cause the excess dissociation of aluminum moieties, which destroys the mucoadhesive paste-forming property.

Chitosan-based gastrointestinal delivery systems

Chitosan, a natural polymer obtained by alkaline deacetylation of chitin, is non-toxic, biocompatible, and biodegradable. These properties make chitosan a good candidate for the development of conventional and novel gastrointestinal (GI) drug and gene delivery systems. The objective of this review is to summarize the recent applications of chitosan in oral and/or buccal delivery, stomach-specific drug delivery, intestinal delivery, and colon-specific drug delivery. The use of chitosan for targeting of drugs to each of these sites in the GI tract is illustrated by examples supported by in vivo studies. Chitosan appears to be a promising material for GI drug and gene delivery applications as many derivatives and formulations are being examined.

Stomach-specific anti-H. pylori therapy. I: Preparation and characterization of tetracyline-loaded chitosan microspheres

The main objective of the study was to develop a stomach-specific drug delivery system to increase the efficacy of tetracycline against Helicobacter pylori. Chitosan microspheres were prepared by ionic cross-linking and precipitation with sodium sulfate. Two different methods were used for drug loading. In method I, tetracycline was mixed with chitosan solution before the simultaneous cross-linking and precipitation. In method II, the drug was incubated with pre-formed microspheres for 48 h. The cumulative amount of tetracycline that was released from chitosan microspheres and the stability of the drug was examined in different pH medium at 37 degrees C. Microspheres with a spherical shape and an average diameter of 2.0-3.0 microm were formed. When the drug was added to the polymer solution before cross-linking and precipitation only 8% (w/w) was optimally incorporated in the final microsphere formulation. When the drug was incubated with the pre-formed microspheres, on the other hand, a maximum of 69% (w/w) could be loaded. Thirty percent of tetracycline either in solution or when released from microspheres was found to degrade at pH 1.2 in 12 h. The preliminary results from this study suggest that chitosan microspheres can be used to incorporate antibiotic drugs and may be effective when administered locally in the stomach against H. pylori.

Evaluation of the factors influencing stomach-specific delivery of antibacterial agents for Helicobacter pylori infection

Because Helicobacter pylori infection is localized in the gastric mucus layer and at the mucus layer-epithelial cell interface, we have developed amoxycillin- and metronidazole-containing chitosan microspheres for stomach-specific drug delivery. Drug-loaded porous chitosan microspheres were prepared by simultaneous crosslinking and precipitation with sodium tripolyphosphate. The release of antibacterial agents into simulated gastric fluid (SGF, pH 1.2), and the stability and permeability through gastric mucin, were examined at 37 degrees C. Because of the high porosity of drug-loaded chitosan microspheres, all the amoxycillin and metronidazole were released in 2 h. High-performance liquid chromatography assays of the antibacterial agents in SGF at 37 degrees C indicated 40% degradation of amoxycillin after 10 h. Metronidazole was completely stable for up to 24 h in SGF. Amoxycillin and metronidazole were highly permeable through the gastric mucin gel layer. The results of this study show that acid-stable antibacterial agents, such as metronidazole, that rapidly permeate the gastric mucus layer would be very effective for the complete eradication of H. pylori infection when delivered specifically at the site of infection in the stomach.