Double-phase hydrogel for buccal delivery of tramadol

Treatment of chronic pain is complicated by the evidence that abuse of prescription opioids is rising; therefore, in many cases, chronic pain remains undertreated. Tramadol is an atypical central analgesic with a mixed mechanism of action offering many advantages over conventional opioids.

We exploited the nonopioid action of tramadol, by bypassing the first-pass effect, as well as multiparticulate drug delivery. Our aim was to identify optimal formulation parameters for designing polyvinyl alcohol (PVA), single and mixed dual cross-linked tramadol microspheres-loaded hydrogel with adequate bioadhesion and providing controlled drug release for buccal delivery.

Microspheres characterization was done by scanning electron microscopy and infrared spectroscopy. Other investigations comprised the evaluation of yield, drug content, particle size, rheology, swelling, mucoadhesion, release, and permeation studies through biological membranes all together with testing the antinociceptive activity and its attenuation by the antagonist naloxone HCl.

PVA-alginate microspheres (F3)-loaded carbopol hydrogel attained: the highest mucoadhesion time (1436.67 min ± 5.77) and mucin adsorption capacity, shear thinning thixotropic properties with adequate yield value and hysteresis area, best drug release (RE = 84.20 ± 2.07%) and permeation efficiency (PE = 65.30 ± 7.02%). Dissolution and permeation profiles were compared using similarity factor; F3-loaded carbogel had the lowest value. During in vivo study, the nonsignificant difference between the AUC of the groups receiving F3-loaded carbogel buccally with (group 5) and without (group 4) administration of naloxone, and between group 4 and the oral group, showed that the buccal route may arguably provide an alternative safer route of tramadol administration.