Chapter 4: Exam 1 Flashcards
what are the 3 main components to the structure of anesthetics
aromatic ring, intermediate chain, and terminal amine
an aromatic ring contains ___________ properties, has ____________ which allows the anesthetic to penetrate the nerve membrane, and determines the _______________ of the drug
lipophilic
lipid solubility
potency/concentration
an intermediate chain is either an _________ or ___________. it distinguishes the type of ___________ and determines the site of ______________
ester or amide
anesthetic
biotransformation
the terminal amine has _____________ properties, has water solubility that ensures the drug will not precipitate on exposure to ____________, and allows the agent to disperse in the ________ and ___________ fluids
hydrophilic
interstitial fluid
intracellular and extracellular
in natural form, local anesthetics are weak ________ meaning their poorly soluble in water
bases
in cartridges, LA solution is acidified to form stable __________
salts
to be stable in solution, the ph of anesthetic must favor water soluble _________ at the time of injection
cations
this is uncharged or neutral and penetrates nerve membranes
base
this has a positive charge, bind to the receptor site, and effects the duration of the anesthetic
cation
primarily effects diffusion, onset times, and success
ionization
after injection into the tissue, the equilibrium shifts from cationic to ___________ due to pH of normal tissue
neutral base
for the anesthetic to pass through the membrane, RNH+ converts to _____
RN
depleted RN in the _________ causes the equilibrium to produce more RN
extracellular fluid
once anesthetic is exposed to the axoplasm, the equilibrium shift to favor ________
RNH+
__________ ions are available in the axoplasm
hydrogen
blocked channel = no __________ = no impulse
sodium
during the resting stage, __________ ions are bound to receptor sites within the ion channels of cell membranes
calcium (Ca++)
during slow depolarization, local anesthetics compete with _______ to bind to the ion channels and to close off these channels
Ca++
during depolarization, __________ are displaced, which is thought to be the most significant factor responsible for the influx of _________ into the nerve
Ca++
sodium
percentages of RNH+ and RN are manipulated by the ________
pH
local anesthetic solution has more __________ than _________
RNH+
RN
what are the benefits to pH in local anesthetics
great stability
increased solubility
ease of sterilization
increasing the pH of a solution/surrounding tissues with increase __________ molecule concentrations
neutral base
lowering ph will favor ________ concentrations
cation
pKa is a ________________ constant
dissociation
pKa is a measurement of a molecules affinity for _________ ions
H+
if pKa = pH then base concentration = ____________ concentration
cation
what is phase I of cns action of LA
cns excitation
how is pKa determined
henderson hasselbalch equation
what is phase II of cns action of LA
cns depression
what are the two possible pathways of biotransformation
liver or blood
the process where LA drugs are broken down to less toxic or nontoxic metabolites before being excreted
biotransformation
biotransformation follows the pathway of the liver = _________________ system (slow)
p450 isoenzyme
plasma cholinesterase breaks down ______________ and ____________
esters and articaine
biotransformation follows pathway of blood = plasma _______________-
cholinesterase
plasma cholinesterase is made by the ____________ but distributed throughout the body
liver
biotransformation of amides is primarily performed by _____________ enzymes
liver hepatic
what is the exception to biotransformation of amides
articaine
biotransformation of esters happens in the blood by ________________
plasma cholinesterase
esters break down into _______________ acid which is thought to be the source of their antigenic tendencies
paraamino benzoic
what is the only injectable ester anesthetic
procaine
elimination of local anesthetics is performed by the ___________
kidneys
