Determination of the stability constant for the inclusion complex between beta-cyclodextrin and nicotine using capillary electrophoresis

Capillary electrophoresis has been employed in order to determine the stability constant for the inclusion complex between beta-cyclodextrin (beta B-CD) and nicotine. The investigation has been performed in aqueous solution at 25 and 37 degrees C and 100 mM ionic strength in a pH interval (5.7 less than or equal to pH less than or equal to 9.6) relevant for systemic delivery of drugs via the oral mucosa. It has been shown that neutral nicotine binds considerably stronger than charged monoprotonated nicotine to beta-CD: K-1 = 22 +/- 12 M-1, K-2 = 242 +/- 11 M-1 (25 degrees C) and K-1 = 22 +/- 12 M-1, K-2 = 194 +/- 10 M-1 (37 degrees C) (K-1 and K-2 refer to complexation by monoprotonated and neutral nicotine, respectively). Oral nicotine absorption from a sublingual tablet containing beta-CD-bound nicotine is briefly discussed in connection with the use of this tablet in smoking cessation therapy. (C) 1997 Elsevier Science B.V.