Week Four: Local Anaesthetic Types Flashcards
What is intrinsic anaesthetic potency?
Concentration and lipid solubility
What is ‘onset of anaesthesia?’
Dependant on speed agent passes through the tissue, proximity to the injection site to target nerve and diameter of nerve fibres
What is ‘duration of action’?
Dependant on rate of diffusion away from target site, related to protein binding affinity & presence absence of a vasoconstrictor
What is ‘effects on other tissues?’
Effects excitable tissues. Could see toxic affects on the cardiovascular system and nervous system.
What is ‘Rate of degradation and elimination?’
- Amides broken down in the liver, significant liver disease and other drugs may effect the rate it is broken down, and subsequently how long it takes to be removed from the body.
- Significant kidney disease may also impact this.
Concerns with LA and pregnancy?
LA can cross the placental barrier.
Topical Anaesthetics: What is available?
Various agents are available today for topical analgesia.
Topical Anaesthetics. General onset time and duration?
Onset time: 2-5 minutes
Duration: 15-20minutes
General indications of topical anaesthetics?
- Anaesthetise mucous membranes
- Surface anaesthesia of gingiva prior to injections
Contraindications of topical anaesthetic?
Known allergy
Precautions of Topical?
Overdose, eating or drinking.
What are some examples of topical anaesthetics?
Xylocaine® 10% special adhesive
- Active ingredient: lignocaine
Xylocaine®5% ointment
◦ Active ingredient: lignocaine
Xylocaine® spray
Num ®
◦ Active ingredient: benzocaine
Oroqix ® (periodontal gel)
◦ Active ingredient: lignocaine and 2.5%/2.5%
◦ Periodontal Gel is supplied in dental cartridges that provide 1.7 g gel.
◦ For use on adults
◦ Thermosetting abilities, thus retained in pockets
What are the six basic components of local anaesthetic?
- Anaesthetic Agent (weak organic base- insoluble in water)
- Stabilisers- salts (converts agent so it is water soluble)
◦ Usually the hydrochlorides - Vasoconstrictors (increase duration of action of L.A)
- Antioxidants (prevents oxidation of stabiliser)
◦ Sodium metabisulphite - Preservatives
• Fungicides, antibacterials
• Methylparaben - Water
◦ Distilled water, increases volume of solution
Vasoconstrictors are added to local anaesthetics for?
- Longer lasting L.A
- More profound L.A
- Reduced operative haemorrhage
- Reduced systemic effects
What type of vasoconstrictors are used in dentistry usually?
- Sympathomimetics (adrenaline) or
* Synthetic polypeptides (octapressin/felypressin)
What is adrenaline?
Naturally occurs in the body
Binds to adrenoreceptors and exerts its effect on a number of body
systems
Sympathomimetic
What is the action of adrenaline in the heart?
• Acts on β1 receptors increases HR and contractility thereby
increasing CO, acts on β2 for coronary artery dilation
• Increase CO, increased BP
What is the action of adrenalin on blood vessels?
• Produces vasoconstriction by acting on the on blood vessels
• α 1 and α2 produce constriction of skin and mucous membranes, β2
results in skeletal muscle vasodilation
What is the effect of adrenaline on the lungs?
It acts on B2 receptors and leads to bronchiolar muscle relaxation.
What is the effect of adrenaline on the GI tract?
It reduces gut contractility, decreases saliva flow.
What is the effect of adrenaline on metabolism?
It can inhibit insulin release and lead to slightly elevated levels of circulating glucose.
What does Felypressin do?
Felypressin causes vasoconstriction by acting on smooth muscle of the vascular beds, with greater effects on the venous side of the peripheral circulation.
Why is Felypressin indicated for some patients.
Felypressin is appropriate for patients when adrenaline is contraindicated.
Name ‘amide’ type local anaesthetics.
Lidocaine/Lignocaine Articaine Prilocaine Mepivacaine Bupivacaine
What are the pharmacological properties of lidocaine/lignocaine?
Highly lipophilic therefore rapidly adsorbed and short onset of action
What is the metabolism of lidocaine/lignocaine?
(95%) Hepatic
What is the elimination half life of lidocain/lignocaine?
90-120minutes