MOA OF LA
blocking sodium channels → prevent influx of sodium ions
how to achieve selectivity of LA
by delivering LA to a limited area
why do we need to achieve selectivity for LA
LAs are non-selective, will block any action potential in all neurons
factors affecting action of LA
- size (small > big)
- myelinated > non-myelinated
- sensory > motor
- circumferential > deep nerve trunk
how does lipid solubulity affect action of LA
more hydrophobic → more potent → longer half life
which transmissions are blocked first
nociceptive and sympathetic
how does pH affect action of LA
alkaline pH → increased LA activity
acidic pH → decreased LA activity
two types of LA
esters and amides
how and where are ester-type and amide-type LA metabolised
ester → esterases in blood
amide → hepatic enzymes in liver
who cannot tolerate ester-type LA
those with PABA allergy
who cannot tolerate amide-type LA
those with liver diseases
examples of injected LA
lidocaine, bupivacaine
examples of topical LA
lidocaine, tetracaine, dibucaine
