Ans. b (Prilocaine) (Ref. KDT 5th ed., 325; Anaesthsia by Ajay Yadav 3rd ed., 218-appendix; 114)Local anesthetic is associated with the risk of Methemoglobinemia- Prilocaine.PRILOCAINE# Prilocaine is an amide type local anesthetic agent.# Safest Local Anesthetic# Metabolized in liver, kidney and lung# Maximum safest dose is 5 mg/kg with adrenaline 8 mg/kg# Most suitable for Bier's block (0.5%)# Methemoglobinemia occurs at higher dose (prilocaine is unique amongst the local anesthetic agents for its ability to reduce the blood's oxygen carrying capacity to cause clinically detectable cyanosis.)# Stored in cool place# Metabolized by pseudocholine esterase# Agent of choice in patients with history of malignant hyperthermia.# It is the first synthetic local anesthetic introduced in 1905.# Practically, it is not used today.# Prilocaine can however be used for Bier's block (or intravenous regional anaesthesia--IVRA). No serious complications have been documented.# Equipotent with lignocaine, but its duration of action is longer and it is less toxic.# It is not a surface anesthetic.Chart 1: Drug capable of inducing methemoglobinemia AcetaminophenAnti malaria drugsNitratesNitric oxidep-Aminislicylic acidChloroquineAmmonum nitrateNitrous oxideLocal anestheticsPrimaquineSilver nitratePiperazineBenzocaineQuinacrineSodium nitrateRifampinBupivacaineMethylene blueNitroglycerineRiluzoleLidocaineDapsoneNitroprussideSulfonamidesPolocainePhenacetinsBismuth subnitrateSulfasalazineEMLA*PhenazopyndineNitntesSulfamethoxazoleAnticonvusantsFlutamideAmyl nitrateSulfadiazineVaiproic acidHydroxylamineIsobutyl nitrateSulfapyridinePhenytoinOral hypoglycemicMetochlopramideNitrofurantoinSulfonesSulfanilamide