12- Local Anestetic Flashcards
What are local anesthetics
Reversible loss of sensation in a region in the body without loss of consciousness
How to local anesthetics to work
Reversibly disrupt the propagation of nerve impulses
Advantages of local anesthetics
Breathing unaffected
Full cv function
How do local anesthetics work
Competitive blockade of sodium gated channel
Two types of linkages
Amine
Ester
Amide link
Can be interfered by hepatic cyp enzymes
Ester type agents are degraded by
Esterase enzymes (AChE inhibitors)
All agents are acids or bases
Bases
What form do all agents exist in
Protonated and deprotonated
Advantages of neutral form of drug
Improved potency and onset
Does pH have an effect on how anesthetics act
Yes
Where do anesthetics block
Vintage gated Na channels
Bind within channel pore
Determinate’s of anesthetisia action
Placement of drug
Tissue environment
Electrolytes
What does K and Na affect
Resting membrane potential
What does Ca affect
Membrane potential
Considerations for local anesthetics
Lipid solubility
Protein binding
Considerations for local anesthetics
Potency Onset time Duration of action CNS toxicity Cvs toxicity
Ester type drugs
Procaine
Tetracaine
Proparacaine
Amide type
Lidocaine
Bupivaccaime
Mepivacaime
Benzocaine
Lidocaine
Very stable Hepaticly metabolized Active metabolites Many routes of admin Cats handle differently
Adverse lidocaine
CNS signs at low conc
Cvs effects at high conc
Goats are more prone to CNS signs
Bupivacaine
Longer lasting
Amide type
Nerve block
More cardio toxic
Mepivacaine
Use in horses
Amide type
