Local anesthetics Flashcards
Potency of Local Anesthetic determines by-
Lipid solubility
Why is Bupivicaine formulates in 0.25% vs lidocaine in 1-2%?
Because buoivicaine is more lipid soluble and 4 Times more potent than lidocaine
What determines duration of local anesthetics? And what does this mean? It’s also influenced by what?
Protein binding. It means that local anesthetics with a higher affinity its for protein remain bound longer to the sodium channel. The degree of binding depends on addition of larger chemical radicals to amine or aromatic end-for example Buoi is 95% protein bound. S lidocaine 65% protein bound
Speed of onset of local anesthetics depends on what?
PKA. Closer pKA of the local anesthetic is to tissue pH, the more rapid the onset time.
What is the definition of pKA?
pH at which 50% of the molecules exist in the unionized lipid Simple tertiary form, and 50% in ionized quaternary water soluble form
The percentage of local anesthetic present in the unionized form when injected into tissue is ________ proportional to its pKA.
Inversely. LA with pKA closer to physiologic pH will have a higher concentration of unionized lipid soluble base-therefore more molecules can cross the lipid membrane into the axoplasm, yielding a faster speed of onset
Why is mepivicaine not used in OB?
Metabolism is prolonged in the fetus.
Mepivicaine vs lidocaine?
Slightly longer DOA compared to lidocaine
Lidocaine Lipid solubility
3
Lidocaine Protein binding?
65%
Lidocaine pKA?
7.8
Bupivicaine lipid solubility
28
Bupivicaine protein binding
95%
Bupivicaine pKA
8.1
Rooivicaine Lipid solubility
14
