LOCAL ANESTHETICS Flashcards
IN A NUTSHELL HOW DO LA’S WORK?
LA PRODUCE A REVERSIBLE, DOSE DEPENDENT BLOCKADE OF SODIUM ION INFLUX INTO NERVE CYTOPLASM. THEY PREVENT SODIUM FROM ENTERING THE NEURON AND FIRING.
WHAT ARE THE 2 MAIN STRUCTURES OF LA AND HOW ARE THEY METABOLIZED?
ESTERS-MET. BY PLASMA CHOLINESTERASE IN BLOOD.
AMIDES- MET. BY LIVER ENZYMES CP450
WHAT IS THE STRUCTURE OF AN LA….AND WHY IS IT IMPORTANT?
THERE ARE 3 ESSENTIAL UNITS…1HYDROPHILIC CHAIN JOINED TO A 2. LIPOPHILIC PORTION BY A 3. ESTER/AMIDE LINKAGE. THIS STRUCTURE ALLOWS LA TO PASS BOTH WATER AND LIPID SOLUBLE MEMBRANES WHICH IS CRUCIAL FOR ITS ACTION AND TO TAKE EFFECT.
WHAT IS THE PKA OF LA (RANGE) AND WHAT DOES THIS MEAN?
PKA=7.6-9
IN AN ACIDIC ENVIORNMENT LIKE INFECTED TISSUE, THE IONIZED PORTION IS INCREASED AND DECREASES ONSET/EFFICACY. IN A BASIC MEDIUM THE UNIONIZED FORM IS INCREASED AND ABSORPTION IS ENHANCED. IN A NUTSHELL…THE NON IONIZED FORM IS ESSENTIAL FOR PENETRATION TO NEURONS BUT ONCE IN THE INTRA AXONAL PH MEDIUM THE DRUG IS PRONATED AND IT IS THE IONIZED PORTION THAT ACTS ON THE RECEPTOR SITE.
WHAT DETERMINES POTENCY OF A LA?
LIPID SOLUBILITY (AND ALSO VASODILATION POTENTIAL)
WHAT DOES PROTEIN BINDING OF LA AFFECT?
DURATION OF LA
WHAT DETERMINES METABOLISM OF LA?
LINKAGE OF LA…WHETHER IS AN ESTER (CO) OR AMIDE (NHC) LINKAGE.
DO IONIZED AND NONIONIZED FORMS OF LA PLAY IMPORTANT ROLES IN IMPULSE BLOCKADE?
YES!!!!!!
WHAT ARE THE BASIC PRINCIPLES OF THE SPECIFIC RECEPTOR THEORY FOR LA MOA?
LA BLOCK AP PROPAGATION BY THE LA BINDING TO INTERNAL OPENING OF NA CHANNEL AND THESE INTERNAL NA RECEPTORS HAVE A HIGHER AFFINITY FOR THE IONIZED FORM OF THE LA. BUT IN ORDER TO GET INSIDE THE LA MUST FIRST PENETRATE THE CELL MEMBRANE WHICH IS FACILITATED BY THE UNIONIZED FORM OF LA.
WHAT IS THE NEURON ORDER OF BLOCKADE FROM EASIST TO HARDEST TO BLOCK?
BCA (dgba)
WHAT IS THE ORDER OF LA BLOCKADE IN THEMS OF WHAT YOU WILL SEE FROM EARLIST TO LATEST SIGNS?
HINT: ALL STUDENTS MUST PASS
AUTONOMIC, SENSORY, MOTOR, PROPRIOCEPTION
LA POTENCY IS MAINLY A PRODUCT OF……?
LIPID SOLUBILITY
LA DURATION IS MAINLY A PRODUCT OF….?
PROTEIN BINDING
LA PKA=PH OF TISSUE =…..?
FASTER ONSET
FOR LA ABSORPTION=……?
WHAT ARE 3 FACTORS THAT AFFECT ABSORPTION?
ABSORPTION=BEGINNING OF OFFSET.
TISSUE BLOOD FLOW, LIPID SOLUBILITY OF THE AGENT, PT AGE/CV STATUS
