Local Anesthetic Pharm (EB) Flashcards
Local anesthetic amides (5)
lidocaine Bupivacaine Ropivacaine Mepivacaine Prilocaine
Local anesthetic esters (4)
cocaine Procaine Tetracaine Amethocaine
Myelin layer of B nerve fibers? Function? Order of block? Effect?
Myelin layer = light Function = autonomic, preganglionic, sympathetic Order of block = 1 Effect = warmth (vasodilation)
Myelin layer of C nerve fibers? Function? Order of block? Effect? ?
Myelin layer = none Function = pain Order of block =2 Effect = loss of pain sensation
Myelin layer of Adelta nerve fibers? Function? Order of block? Effect? ?
Myelin layer = light Function = pain, temp Order of block = 2 Effect = loss of pain and temp sensation
Myelin layer of Agamma nerve fibers? Function? Order of block? Effect? ?
Myelin layer = moderate Function = muscle tone Order of block = 3 Effect = loss of proprioception
Myelin layer of Abeta nerve fibers? Function? Order of block? Effect? ?
Myelin layer = moderate Function = touch, pressure Order of block = 4 Effect = loss?
Myelin layer of Aalpha nerve fibers? Function? Order of block? Effect? ?
Myelin layer = heavy Function = motor Order of block = 5 Effect = paralysis
How does frequency of stimulation influence the onset of blockade?
traumatized tissue more sensitive to local anes blockade
Order of regional local anes blocking?
proximal regions are blocked sooner than distal regions
Which kind of fibers are blocked first (conventionally)
small sensory fibers are blocked before larger sensory and motor fibers
potency of a local anes is closely correlated to
lipid solubility
What are nerve membranes made out of to help with the potency of local anes?
lipids
What influences the speed of onset of a local anes?
pKa
PKa of local anes
weak bases = 7.6 - 9.1
At tissue pH of 7.4, < 50% of local anesthetics are
nonionized
What form of local anesthetics diffuses across the cell membrane
non-ionized
pH _ in infected tissues?
decreases
Because pH decreases in infected tissues, what happens to the non-ionized fraction of local anes? What happens to the action of localed anes?
reduced non-ionized fraction. Reduced or absent local anes action
Protein binding and duration of action of bupivacaine?
95% protein bound, Long duration
Protein binding and duration of action of lidocaine
65% protein bound, Short duration
Effect of action of local anes on vessels? What effect does this have on the drug?
vasodilation»_space; fastens uptake of drug, shortens duration of effect
Additives to a local anesthetic (3)
vasoconstrictors (epinephrine) Hyaluronidase Bicarbonate
Why is epinephrine added to a local anesthetic?
delayed absorption, prolonged action
Con of adding epinephrine to a local anesthetic?
localized ischemia possible
Why is hyaluronidase added to a local anesthetic?
increasing tissue permeability Facilitates diffusion Rapid onset
Why is bicarbonate added to a local anesthetic?
buffers G+ Faster diffusion Shortens onset and duration Injection less painful
What metabolized local anes esters into inactive compounds?
plasma cholinesterases
NB to a long IV infusion of amide local anes?
slowly metabolized by the liver so can accumulate after long IV infusion
Pros of loco-regional use of local anesthetics (3)
easy to use Effective and reliable analgesia Minimal systemic effects