Pharmacology of Local Anesthetics Flashcards
What class of local anesthetic is longer-acting?
Amide LAs - Ester LAs are shorter-acting but potentially less toxic
What types of nerve bundles (Mantle/Core) are more susceptible to LAs?
Mantle Bundles - they are placed more proximally
What is the effect of inflammation on tissue pH?
Inflammation lowers tissue pH - thus reducing the effectiveness of most LAs
Injection administration of an LA is used to target what nerves?
Peripheral nerve endings, nerve trunks, or nerve roots
What is the purpose of the inactive form of LAs?
Weak bases that can readily cross the cell membrane in order to bind Na+ channels once active
How should an LA be administered to target only superficial nerves?
Topically
What are the Amide LAs?
Lidocaine, Prilocaine, Articaine, Bupivacaine
True/False. pKa predicts the rate of onset of a LA.
True - Lower pKa indicated faster onset while Higher pKa indicated longer onset
True/False. LAs have antihistaminic, anticholinergic, and antiarrhythmic effects
True - particularly lidocaine
Methemoglobinemia is most associated with what LA?
Prilocaine
What is the effect of lipid solubility on LA potency?
The greater the lipid solubility, the more potent the LA
What Ester LA is considered the longest lasting and used for spinal anesthesia and ophthalmic procedures?
Tetracaine
These types of nerve fibers are most susceptible to LAs.
Pain > Temperature > Light Touch > Deep Pressure > Proprioception
True/False. Myelination has a greater effect on LA effectiveness than fiber diameter.
False. Fiber diameter is more influential than myelination
How do intrinsic neuronal properties influence the effectiveness of LAs?
Small-diameter fibers, myelinated axons, and neurons with hire firing rates are most susceptible to LAs
What are the commonly used topical LAs?
Lidocaine, Benzocaine (only used topically)
A metabolite of this class of local anesthetics may cause serious allergic reactions in some patients.
Ester LAs
What is neuraxial anesthesia?
Administration of an LA directly into the fatty tissue surrounding nerve roots as they exit the spine
What is the active form of an LA?
Charged cationic form
What may be used to reverse cardiac ADRs of LAs?
IV lipid infusion
This vasoconstrictor has fewer cardiac effects than epinephrine, but potentially interacts with tricyclic antidepressants.
Levonordefrin
What are the commonly injected LAs?
Lidocaine, Bupivocaine, Mepivacine, Procaine
What effect does vasodilation have on LA effect?
Most LAs as vasodilators. This reduces the time LAs are within tissues and decreases their duration of action
What is the effect of low pH on the effectiveness of LAs?
Low pH favors the active form of LAs. This means there is less of the LA in inactive form to cross the cell membrane. The result is longer induction and lower effectiveness
What vasoconstrictors are commonly administered with LAs?
Epinephrine, Levenordefrin
What is the only LA that is a vasoconstrictor, rather than vasodilator?
Cocaine
True/False. Greater protein binding increases the effectiveness of LAs.
False. The higher the degree of protein binding, the less effective the LA
What is the MOA of LAs?
Bind inside voltage-gated Na+ channels to block initiation and propagation of action potentials
What are the most common cardiac ADRs associated with LA use?
Bradycardia, hypotension, shock
What are the common Ester LAs?
Procaine, Chloroprocaine, Tetracaine, Benzocaine, Proparacaine