In-vitro characterization of buccal iontophoresis: The case of sumatriptan succinate

Buccal administration of sumatriptan succinate might be an interesting alternative to the present administration routes, due to its non-invasiveness and rapid onset of action, but because of its low permeability, a permeation enhancement strategy is required. The aim of this work was then to study, in-vitro, buccal iontophoresis of sumatriptan succinate. Permeation experiments were performed in-vitro across pig esophageal epithelium, a recently proposed model of human buccal mucosa, using vertical diffusion cells. The iontophoretic behavior of the tissue was characterized by measuring its isoelectric point (Na+ transport number and the electroosmotic flow of acetaminophen determination) and by evaluating tissue integrity after current application. The results obtained confirm the usefulness of pig esophageal epithelium as an in-vitro model membrane for buccal drug delivery. The application of iontophoresis increased sumatriptan transport, proportionally to the current density applied, without tissue damage: electrotransport was the predominant mechanism. Integrating the results of the present work with literature data on the transport of other molecules across the buccal mucosa and across the skin, we can draw a general conclusion: the difference in passive transport across buccal mucosa and across the skin is influenced by permeant lipophilicity and by the penetration pathway. Finally, buccal iontophoretic administration of sumatriptan allows to administer 6 mg of the drug in 1 h, representing a promising alternative to the current administration routes.