Flashcards in Pharmocology Deck (18)
What is an LA cartridge?
anaesthetic agent, vasoconstrictor, preservative/stabiliser, isotonic carrier medium,
Name 3 UK trade names for lidocaine and adrenaline
Utilycaine, Lignospan Special, Xylocaine
Name 2 UK trade names for articaine and adrenaline
Bartinest and Septanest
Describe the structure of LA
Lipophilic part, intermediate chain, hydrophilic
What are the 2 different types of molecular structures within the intermediate chain?
Ester and Amide
What is the main action of a local anaesthetic?
REVERSIBLY blocky sodium channel so that action potentials cannot occur along the nerve
What are the 2 theories for how local anaesthetics work?
Specific receptor theory
Membrane expansion theory
Describe the membrane expansion theory
local anaesthetic diffuses into the membrane of the axon and prevents the sodium channels from opening
Describe the specific receptor theory
Local anaesthetic bind sodium channel and inactivates it
What is the key point of the specific receptor theory?
LA accesses the sodium channel from inside
Why must LA be lipophilic?
to be able to pass through the axon membrane
Why must LA be hydrophilic?
to be able to bind to the sodium channel
What 2 states does LA exist in?
Charged and uncharged
What does the proportion of charged and uncharged depend on?
the pKa of the drug and the pH of the environment
What does it mean if an LA has a low pKa?
more uncharged drug and so can pass through the axon membrane more rapidly
Name 4 properties of LA
Disassociation and solubility
What type of nerve fibres are the easiest to block?