In vitro and in vivo evaluation of a new sublingual tablet system for rapid oromucosal absorption using fentanyl citrate as the active substance.

Oromucosal delivery of drugs promotes rapid absorption and high bioavailability, with subsequent almost immediate onset of pharmacological effect. However, many oromucosal delivery systems are compromised by the possibility of the patient swallowing the active substance before it has been released and absorbed locally into the systemic circulation. This paper introduces a new tablet system for sublingual administration and rapid drug absorption. The tablet is based on interactive mixtures of components, consisting of carrier particles partially covered by fine dry particles of the drug, in this case fentanyl citrate. In the interests of increasing retention of the drug at the site of absorption in the oral cavity, a bioadhesive component was also added to the carrier particles. Tablets containing 100, 200 and 400 microg of fentanyl were tested both in vitro and in vivo. The tablets disintegrated rapidly and dissolution tests revealed that fentanyl citrate was dissolved from the formulation almost instantly. Plasma concentrations of fentanyl were obtained within 10 min, with no second peak. These results indicated that the bioadhesive component prevented the fentanyl from being swallowed (the fraction swallowed was considered smaller compared to other mucosal delivery systems), without hindering its release and absorption. This new sublingual tablet formulation may also hold potential for other substances where a rapid onset of effect is desirable.