The short half-life and bitter taste of
carbinoxamine maleate2 (CAM) lead to poor compliance by pediatric patients who are being treated for
allergic rhinitis. To address these issues,
carbinoxamine-resin complexes3 (
CRCs) were prepared by ion exchange and then coated with Kollicoat SR 30D. The resultant microencapsulated
carbinoxamine-resin complexes4 (MCRCs) were dispersed into the medium to obtain the final
suspensions. The
drug loading kinetics and thermodynamics of
CRCs, anti-swelling mechanism of the impregnant in MCRCs, in vitro release, and in vivo pharmacokinetics of the
suspensions were systematically evaluated. The
drug loading process was found to obey a first-order kinetic process that was spontaneous, entropy-reduced and exothermic, and the diffusion of CAM into the resin was the rate-limiting step. During microencapsulation, the impregnant could create a certain
buffer space to control the swelling of
CRCs and maintain the coating film intact. The homemade preparations had release behaviors similar to that of the reference in vitro and achieved sustained release in vivo. The low
drug loading preparation had a higher relative bioavailability of 109% owing to its faster release and better dispersibility. Therefore, the
suspensions based on MCRCs could be successfully applied to treating
allergic rhinitis in children.