The feasibility of [P(AA-co-PEGMM)] film as a buccal mucoadhesive patch was previously reported by estimating mucoadhesiveness and release characteristics. To find a rational penetration enhancer of [P(AA-co-PEGMM)] film containing butorphanol tartrate (Bt), penetration of Bt from [P(AA-co-PEGMM)] film which contained various additives was estimated by measuring its flux, Papp and lag tme in in vitro buccal membrane of porcine. EDTA showed almost no increase of Bt permeability, wherease SGC, STDHF and SLS increased the permeability of Bt with the order of SGC > STDHF > SLS. The rational additive concentration of SGC was 4% and its Papp and lag time were $1.93{ imes}10^{-4}{pm}4.21{ imes}10^{-6},;126.60{pm}21.88min;(control;:;Papp;0.45{ imes}10^{-4};;lag;time;211.01{pm}16.77;min)$, respectively.