Factors and strategies for improving buccal absorption of peptides

Buccal transport of flecainide and sotalol: effect of a bile salt and ionization state

Patients with infrequent attacks of supraventricular arrhythmia may benefit from self administration of antiarrhythmic drugs on an 'as required' basis. The oral cavity is easily accessible and the potential for rapid absorption exists. The effects of ionization state and sodium glycocholate on the ex vivo transport of sotalol and flecainide across porcine buccal mucosa were studied. The permeated amounts at 3 h (Q) and fluxes (J) of sotalol in an aqueous solution at pH 7.4 and 9.0 were similar. At pH 7.4, in contrast to pH 9.0, the addition of 1.0% (w/v) sodium glycocholate decreased Q and J four and five fold. Flecainide base in propylene glycol resulted in a nine and 12 fold higher Q and J as compared with an aqueous solution of flecainide acetate at pH 5.8. The presence of sodium glycocholate reduced the transport rate of the flecainide base. However, Q and J were increased 110 and 75 fold by adding 1.0% (w/v) sodium glycocholate to a solution of flecainide acetate at pH 5.8. Sodium glycocholate seems to be an effective penetration enhancer for the buccal absorption of the more polar ionized form of flecainide in an aqueous solution. Sodium glycocholate does not seem to improve the transport of sotalol.

New horizons--alternative routes for insulin therapy

Since the introduction of insulin therapy 80 years ago, the lives of millions of patients with diabetes have been saved, prolonged and immeasurably improved. However, restoring normal glucose levels in diabetic patients through administering insulin by subcutaneous injection has proved virtually impossible. The consequences for patients are serious complications, including diabetic retinopathy and nephropathy, which tend to result from persistent hyperglycaemia. Maximizing glucose control in diabetic patients requires several daily injections. In an effort to reduce this burden, alternative and less-intrusive routes for the administration of insulin are being explored.

The effect of enzyme inhibitor and absorption site following [D-ala2, D-leu5]enkephalin oral administration in rats

The effects of enzyme inhibitor, amastatin, and absorption site following intravenous (i.v.) oral (p.o.), jejunal and ileal administration of [D-ala(2), D-leu(5)]enkephalin (YdAGFdL) were investigated in rats. Model dependent and independent pharmacokinetic parameters were obtained and compared. Linear pharmacokinetics of YdAGFdL were evaluated at 0.28 and 500 microg doses for i.v. and at 1, 500, and 1000 microg for p.o. and ileal routes. Plasma samples were collected and assayed for intact YdAGFdL using a radiometric thin layer chromatography. The clearance (CL) and half lives of the distribution and elimination phases following the 0.28 microg (n=6) i.v. dose were 42.7+/-26.2 (S.D.) ml/min, 0.48+/-0.17 min, and 3.98+/-0.92 min, while those of the 500 microg dose (n=6) were 48.0+/-23.3 ml/min, 0.59+/-0.25, and 6.81+/-3.12 min, respectively, suggesting apparent linear kinetics. The CL values were close to the cardiac output of rats (50 ml/min) indicating very rapid elimination from the body. Mean bioavailability (F) values following p.o. (n=15), jejunal (n=4), and ileal (n=16) administration were 0.40+/-0.24% (S.E.), 1.25+/-0.39, and 1.78+/-0.40, respectively, and were not significantly different (p<0.05) among three doses (1, 1000, 5000 microg). The F value of YdAGFdL following ileal administration in the presence of amastatin was 8.76+/-4.47% (n=6), a 22 fold increase over po administration and a five fold increase over ileal administration without an inhibitor. These results indicate that 'effective' oral delivery of small peptides may be achievable.

The potential of chitosan in enhancing peptide and protein absorption across the TR146 cell culture model-an in vitro model of the buccal epithelium

PURPOSE

To investigate the potential of chitosan (CS) to enhance buccal peptide and protein absorption, the TR146 cell culture model, a model of the buccal epithelium, was used.

METHODS

The sensitivity of TR146 cells to several CS solutions (different salts with different MW) was investigated by using the MTS/ PMS assay. Permeability studies were performed to determine the enhancing effect of CS glutamate (1, 20, 40, 60, and 100 microg/mL) on the permeability of 3H-mannitol and fluorescein isothiocyanate labeled dextrans (FD) with various MW (4.4-19.5 kD) across the cell culture model.

RESULTS

Sensitivity of TR146 cells to CS solutions depended on the concentration, the pH, and the type of CS salt. CS glutamate solutions (pH 6.0) were found to be the least harmful. CS glutamate was able to increase the permeability of model substances with MW up to 9.5 kD across the cell model. An enhancing effect was found for CS concentrations of 20 microg/mL and higher, correlating with a decrease in TEER values. The 20 microg/mL CS concentration had a negligible effect on the enzyme activity of the cells as determined by the MTS/PMS assay.

CONCLUSIONS

CS glutamate is effective in enhancing the transport of macromolecules across the buccal TR146 cell culture model. Therefore. it might be a promising vehicle for peptide and protein buccal administration.