Local anesthetics

Question 1

Ester anesthetic

Answer 1

C: Ester
M: Nonionized form crosses axonal membrane; ionized form (active form) blocks intracellular portion of inactive (refractory) voltage-gated sodium channel
T: Local anesthesia
SE: Local: transient neurologic symptoms (basically, really bad pain), neuronal injury. Systemic (more common with long-acting local anesthetics): CNS (early excitation: decreased inhibition, sensory disturbances, restlessness, tremor, tinnitus; later depression: lethargy, hypotension, seizures), cardiovascular (reduced conductivity, excitability, and contractility; arrhythmias (QRS widening an early sign); indirect vasodilation and bradycardia.** Methemoglobinemia (primarily with benzocaine and prilocaine)
MISC: Cocaine, procaine, benzocaine more likely to have allergic reaction than amides due to containing PABA derivitives; used less frequently than amides; metabolized by plasma esterases

Question 2

Amide anesthetic

Answer 2

C: Amide
M: Nonionized form crosses axonal membrane; ionized form (active form) blocks intracellular portion of inactive (refractory) voltage-gated sodium channel
T: Local anesthesia
SE: Local: transient neurologic symptoms (basically, really bad pain); neuronal injury Systemic (more common with long-acting local anesthetics): CNS (early excitation: decreased inhibition, sensory disturbances, restlessness, tremor, tinnitus; later depression: lethargy, hypotension, seizures); cardiovascular (reduced conductivity, excitability, and contractility; arrhythmias (QRS widening an early sign); indirect vasodilation and bradycardia ** Methemoglobinemia (primarily with benzocaine and prilocaine)
MISC: Lidocaine, mepivicaine, bupivicaine, etidocaine, prilocaine, ropivicaine, dibucaine (names have 2 or more “i”s; metabolized in liver, cleared by kidneys