Mucosal delivery of macromolecules

Oromucosal delivery of macromolecules: Challenges and recent developments to improve bioavailability

Owing to their biological diversity, high potency, good tolerability, low immunogenicity, site-specific activity, and great efficacy, macromolecular drugs (i.e., proteins and peptides, antibodies, hormones, nucleic acids, vaccines, etc.) are extensively used as diagnostics, prophylactics, and therapeutics in various diseases. To overcome drawbacks associated with parenteral (invasive) delivery of macromolecules as well as to preserve their therapeutic integrity, oromucosal route (sublingual and buccal) has been proven efficient alternate port of delivery. This review aims to summarize challenges associated with oromucosal route and overtime developments in conventional delivery systems with special emphasis on most recent delivery strategies. Over the past few decades, significant efforts have been made for improving the oromucosal absorption of macromolecules by employing chemical penetration enhancers (CPE), enzyme inhibitors, chemical modification of drug structure (i.e., lipidation, PEGylation, etc.), and mucoadhesive materials in the form of buccal tablets, films (or patches), sprays, fast disintegrating tablets, and microneedles. Adaptation of adjunct strategies (e.g., iontophoresis in conjunction with CPE) has shown significant improvement in oromucosal absorption of macromolecules; however, these approaches were also associated with many drawbacks. To overcome these shortcomings and to further improve therapeutic outcomes, specialized delivery devices called "hybrid nanosystems" have been designed in recent times. This newer intervention showed promising potential for promoting oromucosal absorption and absolute bioavailability of macromolecules along with improved thermostability (cold chain free storage), enabling self-administration, site-specific activity, improving therapeutic efficacy and patient compliance. We anticipate that tailoring of hybrid nanosystems to clinical trials as well as establishing their short- and long-term safety profile would substantiate their therapeutic value as pharmaceutical devices for oromucosal delivery of macromolecules.

Formulation and evaluation of buccoadhesive quetiapine fumarate tablets

The aim of present study was to develop and evaluate buccoadhesive Quetiapine Fumarate (QF) tablets, which is extensively metabolised by liver. Buccoadhesive tablets of QF were prepared using HPMC K4M, HPMC K15M and combination of carbopol and HPC as mucoadhesive polymers by direct compression method. Sodium deoxycholate was added to formulation to improve the permeation of drug. The formulations were tested for bioadhesion strength, ex vivo residence time, swelling time and in vitro dissolution studies and ex vivo permeation studies. Optimized formulation (F3) showed 92% in vitro release in 8 h and 67% permeation of drug through porcine buccal mucosa and followed fickian release mechanism with zero order kinetics. FTIR studies of optimized formulation showed no evidence of interaction between the drug and polymers. In vivo mucoadhesive behaviour of optimized formulation was performed and subjective parameters were evaluated.

Formulation and evaluation of bioadhesive buccal drug delivery of tizanidine hydrochloride tablets

The study aim was concerned with formulation and evaluation of bioadhesive buccal drug delivery of tizanidine hydrochloride tablets, which is extensively metabolized by liver. The tablets were prepared by direct compression using bioadhesive polymers such as hydroxylpropyl methylcellulose K4M, sodium carboxymethyl cellulose alone, and a combination of these two polymers. In order to improve the permeation of drug, different permeation enhancers like beta-cyclodextrin (beta-CD), hydroxylpropyl beta-cyclodextrin (HP-beta-CD), and sodium deoxycholate (SDC) were added to the formulations. The beta-CD and HP-beta-CD were taken in 1:1 molar ratio to drug in formulations. Bioadhesion strength, ex vivo residence time, swelling, and in vitro dissolution studies and ex vivo permeation studies were performed. In vitro release of optimized bioadhesive buccal tablet was found to be non-Fickian. SDC was taken in 1%, 2%, and 3% w/w of the total tablet weight. Stability studies in natural saliva indicated that optimized formulation has good stability in human saliva. In vivo mucoadhesive behavior of optimized formulation was performed in five healthy male human volunteers and subjective parameters were evaluated.

Current aspects of pharmacologic application of bile acids

Effects of bile acids and their salts on absorption of other substances Bile acids and their salts increase intestinal absorption of lipids and transmembrane and paracellular transfer of small and endogenous and exogenous polar molecules. It has been established that they are good promotores of insulin absorption through skin and nasal mucose, and of blood-brain barrier transfer of salycilates and quinine. Effects of bile acids and their salts on absorption of other substances and their potential action It has been established that combination of bile acids with amphotericin B has potential Leishmanicideal effect and combination with ciprofloxacine has improved its antibacterial activity against Pseudomonas aeruginosa in vitro. Bile acids pharmacodynamic effects Bile acids have analgesic and hypoglycemic effect They also have anti-HIV effect probably suppressing virus transmission from cell to cell. Conclusion New studies of natural bile acids and new synthetic bile acids have revealed that they are not only adjuvants to existing active principles in pharmaceutical forms, but they can act as new therapeutic agents. However, it is necessary to study their possible mechanisms, but they are not crucial for their therapeutic application. Toxicological and pharmacological studies will determine the role of newly synthetized bile acids and their salts in current therapy.

Factors and strategies for improving buccal absorption of peptides

Peptides and polypeptides have important pharmacological properties but only a limited number (e.g. insulin, oxytocin, vasopressin) have been exploited as therapeutics because of problems related to their delivery. The buccal mucosa offers an alternative route to conventional, parenteral administration. Peptides are generally not well absorbed through mucosae because of their molecular size, hydrophilicity and the low permeability of the membrane. Peptide transport across buccal mucosa occurs via passive diffusion and is often accompanied by varying degrees of metabolism. This review describes various approaches to improve the buccal absorption of peptides including the use of penetration enhancers to increase membrane permeability and/or the addition of enzyme inhibitors to increase their stability. Other strategies including molecular modification with bioreversible chemical groups or specific formulations such as bioadhesive delivery systems are also discussed.

Permeability of antisense oligonucleotide through porcine buccal mucosa

Antisense oligonucleotides (AONs) that can modulate malfunctioning genes have a great potential to become future therapeutic agents. In this study, we investigated the feasibility of buccal delivery of AONs using ISIS 3082 as a model compound. An isocratic HPLC method was developed to quantify ISIS 3082. The permeability coefficient of this AON at 37 degrees C, determined by using side-by-side diffusion cells, was 1.05x10(-9) (cm/s). The flux of ISIS 3082 across buccal mucosa was dependent upon its concentration in the donor chamber. The permeation of ISIS 3082 was increased when 100 mM of sodium glycocholate was used as a permeation enhancer. The potential of delivering AONs via buccal route with the aid of permeation enhancers is explored in this study.

Recent advances in buccal drug delivery and absorption--in vitro and in vivo studies

In the first part of this study, the aim was to characterize transport of fluorescein isothiocyanate (FITC)-labelled dextrans of different molecular weights as model compounds for peptides and proteins through buccal mucosa. The penetration of these dextrans through porcine buccal mucosa (a nonkeratinized epithelium, comparable to human buccal mucosa) was investigated by measuring transbuccal fluxes and by analyzing the distribution of the fluorescent probe in the epithelium, using confocal laser scanning microscopy for visualizing permeation pathways. The results revealed that passage of hydrophilic compounds such as the FITC-dextrans through porcine buccal epithelium is restricted to permeants with a molecular weight lower than 20 kDa. The permeabilities of buccal mucosa for the 4 and 10 kDa FITC-dextran (of the order of 10(-8) cm/s) were not significantly different from each other or from the much smaller compound FITC. The confocal images of the distribution pattern of FITC-dextrans showed that the paracellular route is the major pathway through buccal epithelium. In the in vivo part of this study, buccal delivery of FITC-labelled dextran 4400 (FD4) and the peptide drug buserelin was investigated in vivo, in pigs. The delivery device consisted of an application chamber with a solution of FD4 or buserelin, and was attached to the buccal mucosa for 4 h using an adhesive patch. A randomized cross-over study including intravenous administration and buccal delivery without and with 10 mM sodium glycodeoxycholate (GDC) as an absorption enhancer was performed in pigs. After buccal administration, steady-state plasma levels were rapidly achieved. Co-administration of 10 mM GDC increased the absolute bioavailability from 1.8+/-0.5 to 12.7+/-2.0% for FD4. From the present studies, it is concluded that buccal administration is a suitable route for the delivery for macromolecules and hydrophilic compounds such as peptide drugs.

In-vivo buccal delivery of fluorescein isothiocyanate-dextran 4400 with glycodeoxycholate as an absorption enhancer in pigs

Buccal delivery of fluorescein isothiocyanate labeled dextran 4400 (FD4) was investigated in-vivo in pigs. The delivery device consisted of an application chamber with a solution of FD4 and was adhered to the buccal mucosa for 4 h using an adhesive patch. A randomized crossover study including intravenous administration and buccal delivery without and with 10 mM sodium glycodeoxycholate (GDC) as absorption enhancer was performed in five pigs. After buccal administration, steady state plasma levels were rapidly reached. Coadministration of 10 mM GDC increased the absolute bioavailability of FD4 from 1.8 +/- 0.5% to 12.7 +/- 2.0%. Since FD4 is a macromolecular and hydrophilic compound such as peptide and protein drugs, buccal delivery would provide an adequate alternative to the parenteral administration of these drugs.