Local Anesthetics Flashcards
single most important determining factor in efficacy of local anesthetics
Hydrophobicity – moderate is ideal
class of drugs metabolized in the plasma and tissues by pseudocholinesterases.
Aminoesters
class of drugs metabolized in the liver, lungs and kidneys
aminoamides
stabilize the inactive conformation and increase the refractory period.
local anesthetics – Na channel blockade
fixed ratio of Na channels are blocked at all times. Minimizes blockade of non-pain sensory modalities
Tonic inhibition
Tissues undergoing high frequency stimulation. Degree of inhibition increases with the rate of action potential firing.
phasic inhibition
Diffusion through which neurium is most difficult?
perineurium
least sensitive fibers
muscle
proximal numbing prior to distal
differential blockade
applied prior to suturing small wounds
TAC – tetracaine, epinephrine, cocaine
dental topical anesthetics
Lidocaine and benzocaine
Dental injected anesthetics
lidocaine, mepivacaine, bupivacaine
Dental ideal for pediatrics
Mepivacaine
Dental more potent and longer T1/2 than mepivacaine or lidocaine. Lengthy proceedures and post op. Aminoamide
Bupivacaine
epidural and intrathecal (spinal) anesthesia
central nerve block
may be used to lengthen effect of peripheral nerve block, but caution not to cause hypoxia.
epinephrine
great for epidural but may cause cardiotoxicity
Bupivacaine (Levobupivacaine and ropivacaine may be safer)
proceedure where short acting LA is preferred (lidocaine). Uses tourniquet and distal band on an elevated extremety. No blood, practical time limit, BZ may be coadministered.
Intraveinous regional anesthesia
short acting aminoester – low hydrophobicity. Infiltration anesthesia and dental, or OB
Procaine or 2-Chloroprocaine (OB)
produces PABA metabolite that can act as an allergen and interfere with sulfonamide drugs.
Procaine
amino ester with high hydrophobicity – long acting. Spinal and topical anesthesia
Tetracaine
Medium potency and duration. Profound cardiotoxic potential. Ophthalmic anesthesia and part of TAC.
Cocaine
Most commonly used local anesthetic. Used for everything. AE – drowsiness, tinnitis, twitching, and seizures
Lidocaine
similar to lidocaine, but exibits vasoconstriction. Good for pt in which epinephrine in contraindicated.
Prilocaine
aminoamide with an ester bond – metabolized in both plasma and liver
Articaine
combination of lidocaine and prilocaine – cream or patch, useful in dental (children), venipuncture, lumbar puncture, arterial cannulation. Cocaine induced euphoria
EMLA
Local irritation – skeletal muscle, smooth muscle – biphasic vessels and bronchiols, cardiac tissue – decrease conduction velocities and contractility, CNS – cross BBB initially inducing excitement followed by depression, Immune system – hypersensitive dermatitis and asthma (aminoesters)
major toxicities
