The essential features of esters are:

  • Esters are less stable in solution than amides
  • Metabolism is mainly by plasma cholinesterases
  • The metabolite para-amino benzoic acid (PABA) is thought to be the cause of the higher incidence of hypersensitivity reactions than in the amide group. However, such reactions are rare and have only been reported in individual case reports
  • tetracaine used in single use minims for corneal anaesthesia is an example of a commonly used ester
  • Cocaine is another member of this group.