Tricyclic antidepressants, as
doxepin hydrochloride (DH), may have
analgesic local effect due to its biochemical mechanism of action. Delivery of DH directly to the oral cavity could be an interesting alternative for
toothache due to its
analgesic local effect. One problem associated with the
mucosal administration routes is the short residence time of the
dosage form on the mucosal membranes. In this sense, we have developed new
doxepin mucoadhesive films able of reducing
pain and increasing the effectiveness of treatment. For this purpose, we tested three different
polymers:
chitosan,
sodium hydroxypropylmethylcellulose (HPMC) and
sodium carboxymethylcellulose (SCMC) in film elaboration. The results obtained show that all films are hydrophilic matrices that absorb water when placed in an aqueous media. All the films hydrated very quickly, reaching high percentage of swelling after just few minutes (5 min for SCMC, 2 min for HPMC and 30 min for
chitosan). Moreover, the SCMC and HPMC films were dissolved whereas
chitosan was not dissolved. Dissolution also leads to viscous liquids with a higher retention time over mucosal surfaces what may lead to adhesive interactions. In vitro permeation studies showed that for all the formulations studied, SCMC (19.91%), HPMC (69.5%) and
chitosan (24.17%), the percentage of
drug permeated increased compared to the
drug solution (8.26%). Specifically the HPMC film presents greater amounts of
doxepin permeated (49.27 ± 4.47 µg/cm(2)).