An ester-type local anesthetic agent, benzocaine (BZC), and its metabolite, para-aminobenzoic acid (PABA), both form 1:1 host-guest complexes with cucurbit[7]uril (CB[7]) in aqueous solution and has been observed by 1 H NMR, UV-visible spectroscopic titrations (including Job's Plot), electrospray ionization (ESI) mass spectrometry, and density functional theory (DFT) molecular modeling. The host-guest binding affinities are (2.2 ± 0.2) × 10 4 M-1 and (1.5 ± 0.2) × 10 4 M-1 for protonated BZC and PABA, respectively, in acidic solutions. The binding constants decrease by ~100-fold to approximately 300 and 200 M-1 for BZC and PABA, respectively, upon deprotonation of these guest molecules in PBS buffered solution (pH = 7.4). However, the encapsulation of these guest molecules by CB[7] only resulted in very moderate pKa shift. This supramolecular encapsulation of BZC and PABA could potentially find applications in drugs formulation for the purpose of enhancing bio-absorption as well as reducing methemoglobinemia and allergic reactions caused by the derivation of PABA during metabolism of BZC.