Formulation of oral mucosal drug delivery systems for the systemic delivery of bioactive materials

An Update on Pharmaceutical Strategies for Oral Delivery of Therapeutic Peptides and Proteins in Adults and Pediatrics

While each route of therapeutic drug delivery has its own advantages and limitations, oral delivery is often favored because it offers convenient painless administration, sustained delivery, prolonged shelf life, and often lower manufacturing cost. Its limitations include mucus and epithelial cell barriers in the gastrointestinal (GI) tract that can block access of larger molecules including Therapeutic protein or peptide-based drugs (TPPs), resulting in reduced bioavailability. This review describes these barriers and discusses different strategies used to modify TPPs to enhance their oral bioavailability and/or to increase their absorption. Some seek to stabilize the TTPs to prevent their degradation by proteolytic enzymes in the GI tract by administering them together with protease inhibitors, while others modify TPPs with mucoadhesive polymers like polyethylene glycol (PEG) to allow them to interact with the mucus layer, thereby delaying their clearance. The further barrier provided by the epithelial cell membrane can be overcome by the addition of a cell-penetrating peptide (CPP) and the use of a carrier molecule such as a liposome, microsphere, or nanosphere to transport the TPP-CPP chimera. Enteric coatings have also been used to help TPPs reach the small intestine. Key efficacious TPP formulations that have been approved for clinical use will be discussed.

Electrospun oral formulations for combined photo-chemotherapy of colon cancer

In this work, we report new formulations for the combined photo-chemotherapy of colon cancer. Fibers were fabricated via coaxial-electrospinning with the intent of targeting delivery of the anti-cancer drug carmofur (CAR) and the photosensitizer rose bengal (RB) selectively to the colon site. The fibers comprised a hydroxypropyl methylcellulose (HPMC) core loaded with the active ingredients, and a pH-sensitive Eudragit L100-55 shell. The fibers were found to be homogeneous and cylindrical and have visible core-shell structures. X-ray diffraction and differential scanning calorimetry demonstrated that both CAR and RB were present in the fibers in the amorphous physical form. In vitro drug release studies showed that the fibers have the potential to selectively deliver drugs to the colon, with only 10-15 % release noted in the acidic conditions of the stomach but sustained release at pH 7.4. Cytotoxicity studies were undertaken on human dermal fibroblast (HDF) and colon cancer (Caco-2) cells, and the influence of light on cell death was also explored. The fibers loaded with CAR alone showed obvious toxicity to both cell lines, with and without the application of light. The RB-loaded fibers led to high viability (ca. 80% for both cell types) in the absence of light, but much greater toxicity was noted (30-50%) with light. The same trends were observed with the formulation containing both CAR and RB, but with lower viabilities. The RB and RB/CAR loaded systems show clear selectivity for cancerous over non-cancerous cells. Finally, mucoadhesion studies revealed there were strong adhesive forces between the rat colonic mucosa and the fibers after they had passed through an acidic environment. Such electrospun fibers thus could have potential in the development of oral therapies for colon cancer.

Manufacture and characterization of mucoadhesive buccal films

The buccal route of administration has a number of advantages including bypassing the gastrointestinal tract and the hepatic first pass effect. Mucoadhesive films are retentive dosage forms and release drug directly into a biological substrate. Furthermore, films have improved patient compliance due to their small size and reduced thickness, compared for example to lozenges and tablets. The development of mucoadhesive buccal films has increased dramatically over the past decade because it is a promising delivery alternative to various therapeutic classes including peptides, vaccines, and nanoparticles. The "film casting process" involves casting of aqueous solutions and/or organic solvents to yield films suitable for this administration route. Over the last decade, hot-melt extrusion has been explored as an alternative manufacturing process and has yielded promising results. Characterization of critical properties such as the mucoadhesive strength, drug content uniformity, and permeation rate represent the major research areas in the design of buccal films. This review will consider the literature that describes the manufacture and characterization of mucoadhesive buccal films.

Polymeric microspheres for drug delivery to the oral cavity: an in vitro evaluation of mucoadhesive potential

Polymeric microparticles were fabricated from Carbopol, polycarbophil, chitosan, or Gantrez using a "water-in-oil emulsification" solvent evaporation method. Mean particle sizes, as determined by laser diffraction, were in the range 23-38 microm. Electron microscopy revealed that all microparticles were spherical and of smooth surface morphology. In pH 7.0 phosphate buffered saline, the microspheres exhibited significantly increased swelling ratios and longer half-times of swelling than the corresponding powdered polymers. The relative merits of the potential usefulness of these microspheres as formulation tools for the enhanced retention of a therapeutic entity within the oral mucosa were evaluated by in vitro mucoadhesion tests. Tensile tests showed that all microspheres under consideration were capable of adhering to porcine esophageal mucosa, with particles prepared from the poly(acrylic acid)s exhibiting greater mucoadhesive strength than those constructed from chitosan or Gantrez. However, in elution experiments involving a challenge with artificial saliva, particles of chitosan or Gantrez were retained onto mucosal tissue for longer time periods than those assembled from the poly(acrylic acid)s.

Evaluation of polyoxyethylene homopolymers for buccal bioadhesive drug delivery device formulations

Our objective was to evaluate the application of polyoxyethylene homopolymers in buccal bioadhesive drug (BBD) delivery device formulations. The bioadhesive strength of four different molecular weight (MW) polyoxyethylene polymers was measured by Instron tensile tester using glass plate and bovine sublingual tissue as substrate surfaces. Several BBD device formulations containing polyoxyethylene polymer (MW 7,000,000) were prepared by direct compression and compression molding processes. The prepared BBD devices were evaluated for their elasticity, in vitro adhesion and drug release characteristics. The in vivo bioadhesion characteristics of a placebo compression molded device were examined in 3 adult healthy male beagle dogs. The bioadhesive strength of polyoxyethylene polymers appeared to be directly related to their molecular weights. When bovine sublingual mucosa or a glass plate was used as model mucosal substrate surface, the rank order of bioadhesive strength of different molecular weight polyoxyethylene polymers was similar. The bioadhesive strength of devices prepared by the compression molding process was greater than those prepared by direct compression, but the kinetics of drug release were independent of the process used for the preparation of the devices. The drug release and the bioadhesive strength of the similarly prepared device formulations appeared to be dependent on the drug:polymer ratios. The elasticity of the BBD devices prepared by compression molding was improved by the inclusion of polyisobutylene polymer in the formulations. When adhered to the oral cavity of the dogs, the compression molded placebo BBD device exhibited adhesion for at least 4 hours and appeared to show no signs of local irritation. In conclusion, BBD devices containing polyoxyethylene polymer (MW 7,000,000) can be prepared by direct compression or compression molding process in order to provide controlled drug release to the oral cavity while maintaining appropriate bioadhesive characteristics.

In vitro studies on enhancing effect of sodium glycocholate on transbuccal permeation of morphine hydrochloride

During the perioperative period, gastric emptying rate and first-pass metabolism limit the use of peroral morphine. Buccal mucosa appears to be a potential site for delivery of morphine as it provides direct entry into the system circulation thereby avoiding the hepatic first-pass effect. However, the low permeability of the buccal epithelium results in a low flux of the drug. The use of a penetration enhancer is required to improve the bioavailability of the drug via buccal route. In this study, the enhancing effect of sodium glycocholate (GC) used at 10 mM and 100 mM concentrations on permeation of morphine hydrochloride (MPH) across the porcine buccal mucosa was studied in vitro. Furthermore, in conjunction with its permeation, accumulation of GC in the tissue with time was also studied in order to elucidate the relationship between GC and enhanced mucosal permeation of the drug. Franz diffusion cells were used in the experiments. Permeation of MPH was increased in the presence of 100 mM GC with an enhancement factor of 9.3 whereas no enhancement was obtained with 10 mM GC. The calculated permeability coefficient for MPH in the presence of 100 mM GC was 2.35 x 10(-5) cm/s. Accumulation of GC at 100 mM in the tissue appears to be more significant at 100 mM concentration which correlated well with the increased permeation of the drug. GC was diffused through the buccal epithelium significantly at 100 mM concentration. Interaction of GC with the tissue appears to be more significant at 100 mM concentration compared to 10 mM concentration, thus resulting in a significant enhancing effect.