Permeation enhancers are of major interest to improve the low bioavailability of therapeutic agents due to poor membrane permeation. AT1002, a six-amino acid fragment of Zonula occludens toxin, was reported to possess permeation-enhancing effects. However, further studies were suggested to focus on the peptide nature of AT1002 like stability and membrane clearance to accurately reflect its permeation-enhancing potential. Thus, this paper focused on the susceptibility of AT1002 for identifying additives to minimize the instability of AT1002, and the permeation-enhancing effect of AT1002 when co-administered with a bioadhesive polymer. The stability study showed that AT1002 were unstable in neutral to basic pH conditions and with increasing incubation time, and 5% dextrose and the 1% mixture of amino acids (arginine, cysteine, glycine) significantly minimized the instability of AT1002 at pH 7.4 for at least 6 hours, respectively. In the intranasal study of a paracellular marker, the administration of mannitol with AT1002 in 5% dextrose solution led to statistically significant 3.14- and 2.17-fold increases in $C_{max}$ and $AUC_{0-360min}$ in the presence of carrageenan over the control. Thus, the addition of carrageenan as a bioadhesive polymer and dextrose as a stabilizer together with AT1002 may allow the development of the mucosal drug delivery of low-bioavailability therapeutic agents.