<prompt> The following statements about bupivacaine are true, except:Must never be injected into veinMore cardiotoxic than lignocaine0.25 is effective for sensory blockProduces methemoglobinemia  <response>: Bupivacaine and its congeners - Bupivacaine a long acting local anesthetic is very common in clinical use due to its good capability of differential block. The major demerit is that it is most cardio toxic. It is racemic mixture. Prilocaine is the only local anesthetic that is metabolized to o -toluidine, which conves hemoglobin to methemoglobin producing methemoglobinemia. This is usually significant with doses of prilocaine as large as 600mg. Benzocaine used in topical local anesthetic sprays can also cause dangerous Methemoglobinemia. Treatment of medically impoant methemoglobinemia includes intravenous methylene blue 1-2 mgkg of a 1 solution over 5 min. Methylene blue acts by reducing methemoglobin Fe 3 to hemoglobin Fe 2 . 