Local anaesthetic with maximum ionized form at physiological pH ?

Ans. is 'd' i.e., Chloroprocaine Local anaesthetics with pKa value closest at physiological pH (7.4) will have a higher concentration of nonionized (unionized) base. Thus, the agent with pKa value away from physiological pH will have more concentration of ionized form. Chloroprocaine has highest pKa value, hence maximum ionized form at physiological pH. Local anaesthetics with pKa value in increasing order Mepivacaine (7.6) < Etidocaine (7-7) < Lidocaine (7-8) Prilocaine (7.8) < Bupivacaine (8-1) = Ropivacaine (8-1) < Tetracaine (8.2) < Cocaine (8.7) < Procaine (8.9) < Chloroprocaine (9-0)