THE METABOLISM OF ESTER TYPE LOCAL ANAESTHETICS MAY BE INHIBITED BY ANTICHOLINESTERASES THUS INCRESING THE RISK OF SYSTEMIC TOXICITY. ESTER DERIVATIVES LIKE TETRACAINE, BENZOCAINE & PROCAINE THAT ARE HYDROLYSED TO PARAAMINO BENZOIC ACID MAY ANTAGONISE THE ACTIVITY OF AMINOSALICYLIC ACID OR SULPHONAMIDES. THESE MAY COMPETITIVELY ENHANCE THE NEUROMUSCULAR BLOCKING ACTIVITY OF SUXOMETHONIUM.