Procaine belongs to which class of local anesthetics?

• A. Amide
• B. None
• C. Ester
• D. Both

Answer: (C)

Local anesthetics are categorized by the chemical linkage in their structure into esters and amides. Procaine is an ester-type local anesthetic because it is the ester of para-aminobenzoic acid. This ester linkage means it is rapidly hydrolyzed in the blood by plasma cholinesterases, giving it a relatively short duration of action. Esters tend to have shorter durations and historically have a higher association with allergic reactions related to the PABA metabolite, whereas amide anesthetics (such as lidocaine or bupivacaine) are more resistant to hydrolysis, metabolized mainly in the liver, and generally have longer durations. This combination of rapid breakdown and the ester linkage is why procaine is classified as an ester local anesthetic.