local anesthetics Flashcards
what happens with local anesthetics?
inhibit nerve conduction by blocking Na+ channel
how many functional amines and what are they
lipophilic group
tertiary amine
intermediate chain connecting the two
what was the first local anesthetic?
cocaine- causes vasoconstriction
pharmacokinetics of local anesthetics
pKa is 8-9
pH(7) is < pKa so it will be charged
need a transporter
hendersen haslbach figures percentage of D vs DH
drug is in cell binds to Na and inhibits it which inhibits depolarization
Absorption
dose
site of injection
drug/tissue interaction
local blood flow (use epi to target alpha 1– vasoconstriction)
physio chem drug properties–inflamation… acidosis… more acid region when molecules are basic…
what happens when there is myelination?
sensitivity of nerves to local anesthetic is less
frequency of Na+ channel is spaced out
> distance
< time
what happens when there is no/low myelination?
sensitivity of nerves to local anesthetic is more
metabolism and excretion
ester: via blood esterases
amide: liver via P450 isozymes (up to 15 hr duration)
2-15 min onset for both
liver disease caution
Adverse effects: CNS
CNS: excite followed by depression; convulsions can occur durring excite stage
low dose: sleepy, light head, visual/audio, restless, numbness in toungue
high dose: nystagmus; muscle twitch; convulsions
Adverse effects: Cardiac
suppress excitability in myocardium and conduction
bradycardia
heart block
reduce force
cardiac arrest
relax vasc SM vasodilation and hypotension
what is PABA
para amino benzoic acid… increase risk for allerge
greater chance for allergic rxn in ester or amide
ester – metabolized to PABA which triggers it
topical administration
what drugs
applied to skin/mucous membrane
releive pain, itch, soreness
lidocaine/tetrocaine/procaine
Pramoxine
itching
pramoxine
used with hydrocortisone for rectal hemrrhoids
diclonine
in cough meds; oral anesthetic for cough lozenges/ throat spray
proparacaine
opthalmic local anesthetic
dibucaine
topical anesthetic used in hemmrhoid cream
infiltration (injection) anesthesia
injection of local anesthetic into immediate area of surgery
articaine, bupivicaine (cardio depressant), levobupivicaine(less cardiotoxic), chlorprocaine
how does duration of anesthesia increase?
w/ epinephrine contraindicated in end tissues (toes, fingers, penis) due to restriction of blood flow causing gangrene
nerve block anesthesia
injection of local anesthesia into or near nerve that supplies the surgical area
lidocaine, mepivicaine, levobupivicaine, and ropivicane(3-15 hr duration)
amides have londer duration are chemically stabel
IV anesthesia
- used on extremities
- limit systemic circulation
- lidocaine w/o epi is preferred
epidural anesthesia
avoid preservatives
after inj of local anesthetic into epidural space, which is in spinal column but outside dura mater.
diffusion of anesthetic across dura into subarachnoid space blocks conduction of nerve roots and conduction in spinal cord
lidocaine bupivicaine levobupivicaine
spinal anesthesia
in cerebral spinal fluid in subarachnoid space in the lumbar region below termination of spinal cord
lidocaine, tetracaine, bupivicaine, and levobupivicaine
