LA Pharmacology Flashcards
What is normally in a cartridge?
- usually 2.2ml or 1.8ml
- anaesthetic agent
- vasoconstrictor
- stabilizer / preservative
- isotonic carrier medium
What is the Uk trade name for Lidocaine and what is its vasoconstrictor?
Lidocaine vasoconstrictor is adrenaline
Uk trade name = Lignospan Special™
How do local anaesthetics work?
Action potentials:
– Initial opening of Na+ channels……
– Depolarisation
Therefore – to block Action potentials:
– REVERSIBLY block Na+ channels
What 2 states does Local Anaesthetic exist in?
Exist in 2 states:
Uncharged (lipid soluble) – pass through axon membrane
Charged – binds to sodium channel
LA drugs poorly soluble in aqueous environment
If an LA has a low pKa what happens?
LA has a low pKa:
– More uncharged drug
– Passes through nerve membrane rapidly
What are the Types of Local Anaesthetics?
Lidocaine Gold standard
Prilocaine An alternative
Mepivacaine An alternative - Least vasodilatory
Bupivacaine High protein binding \Long acting
Articaine Relatively new USP: diffusability
What drugs are these drugs classes as : – Lidocaine – Prilocaine – Mepivacaine – Bupivacaine – Articaine
Amides
Why would a Vasoconstrictor be used?
- increase speed of onset
- counteract vasodilatory effects of the LA agent
- extend duration of anaesthesia
- improve depth of anaesthesia
- lower blood levels of LA
- reduce haemorrhage
How to work out max dose for each patient?
Based upon patient weight:
A tenth of a cartridge per Kg for healthy patients
Lidocaine:
– 70Kg average patient
– 70 tenths i.e. 7 cartridges
– Tenth of a cartridge = 4.4mg Lidocaine
– Dose = 308mg
Once max dose reached do not switch to another LA drug
When Do you not use Lidocaine/adrenaline?
Do not use Lidocaine/adrenaline if patient has:
– Unstable angina
– Severe Cardiac dysrhythmia
– Allergy to any components
What is Articaine?
- Amide with an ester group
- Thiophene ring as its lipophilic component – increases lipid solubility
What is the Unique selling point of Articaine?
Ability to diffuse through bone
Can achieve anaesthesia of lower posterior teeth by infiltration
