Local Anaesthetic

Question 1

What is local anaesthetic?

Answer 1

It is the loss of sensation in an area of the body caused by a depression in the excitation of the nerves, or an inhibition of the conduction process in the peripheral nerves.

Question 2

How does LA work?

Answer 2

LA blocks the conduction if electrical impulses along the nerve fibres by decreasing the permeability of the ion channels to sodium ions (Na+).

Question 3

What are the 3 parts of LA molecules?

Answer 3

Lipophilic end
Hydrophilic end
Link between the ends (ester or amide)

Question 4

What is vasodilation?

Answer 4

It is the widening of the blood vessels. It results from the relaxation of smooth muscle cells in the vessel walls.

Vasodilation decreases blood pressure.

Question 5

What is vasoconstriction?

Answer 5

It is the narrowing of blood vessels from contraction of the muscular walls of the vessels.

The opposite of vasodilation.

Question 6

All LA’s have vasodilation effects. What are these?

Answer 6

Increased perfusion at the site.
Increased absorption of LA.
Higher plasma levels of the LA.
Decreased depth of LA and decreased duration of action.
Increased bleeding at the site of treatment.

Question 7

Why are vasoconstrictors added to LA?

Answer 7

They control tissue perfusion and oppose the vasodilatory actions of LA.
They decrease perfusion (blood flow).
Slow the absorption of LA into the cardiovascular system.
Prolongs anaesthesia in the site, meaning less LA needs to be used, therefore lowering toxicity levels.
Decreases bleeding at the administration and treatment site.

Question 8

Most common vasoconstrictors used in dentistry..

Answer 8

Epinephrine
Norepinephrine 
Phenylephrine
Levonordefin
Octapressin

Question 9

5 things about epinephrine and adrenaline…

Answer 9

They are hormones produced by the medulla of the adrenal gland

Powerful vasoconstrictor.

Allow more anaesthetic molecules to diffuse to the nerve membrane and thus improves depth and duration of anaesthesia.

It is the most commonly used in dentistry

Primary action of epinephrine is on the smaller arterioles and pre-capillary sphincters.

Question 10

5 things about norepinephrine and noradrenaline…

Answer 10

Hormone produced by the adrenal medulla.

Similar chemical and pharmacological properties to epinephrine

Produces intense peripheral vasoconstriction with possible dramatic elevation of the blood vessels.

Use of norepinephrine in dentistry is not recommended

Mixing epinephrine and norepinephrine should be absolutely avoided

Question 11

What is phenylephrine used for?

Answer 11

Used as a nasal decongestant

Reduces the size of blood vessels (Vasoconstrictor)

Used in patients with hypotension to increase blood pressure

Not recommended for use in patients with high blood pressure.

Question 12

Things about levonordefrin

Answer 12

Only found in cartridges containing mepivacaine 1:20,000

Levonordefrin weaker than epinephrine but 1:20,000 is 5x stronger than standard concentration of epinephrine.

Question 13

Things about octapressin

Answer 13

Similar properties to vasopressin

Does not predicted ischemia (blanching) at the injection site

Comes in citanest 3% with octapressin

Question 14

Name the esters and amides

Answer 14

Esters: procaine

Amides: articaine, bupivacaine, lidocaine, mepivacaine, prilocaine

Question 15

3 things about LA

Answer 15

LA reversibly blocks conduction alone a nerve distal to the application site.

They are generally classified into chemical structure, rate of onset, potency and duration of action.

Chemically they are either aminoamides or aminoesters.

Question 16

Procaine

Brand name novoacaine

Answer 16

Relatively weak with long onset of action and short duration

Ester (high risk of allergy).
Plain procaine provides no pupal anaesthesia.
Pot-1
Tox-1
Duration-15-30mins of s/t
Onset-6-10mins
High vasodilating properties - the most of all LA’s

Question 17

Lidocaine

Brand names lignocaine, xylocaine, xylocar

Answer 17

Amide
Most versatile and most used due to high potency, rapid onset of action and long duration. Has topical activity. 
Pulpal anaesthesia with plain LA is 5mins
Pot-2
Tox-2
Onset-2-3mins
Duration- 1 hour with vasoconstrictor
3-5hours s/t

Lidocaine 2% with epinephrine 1:50,000 and lidocaine 2% with epinephrine 1:100,000

1:50,000 is stronger and provides better haemostatic properties.

Question 18

Mepivacaine (brand name scandonest)

Answer 18

Amide 
Pot-2
Tox-1.5-2
Onset- 1.5-2mins
Pulpal anaesthesia- 20-40mins (plain) 
60mins with vasoconstrictor 
2-3 hours s/t plain 
3-5hours s/t with vasoconstrictor 

Mepivacaine 3% plain recommended for patients who cannot have vasoconstrictor and for short length appointments where pulp anaesthesia isn’t needed.

Mepivacaine 2% with levonordefrin 1:20,000 or epinephrine 1:100,000

Question 19

Prilocaine (Brand name citanest)

Answer 19

Amide
Pot-2
Tox-1
Onset 2-4mins
Prilocaine plain pulpal anaesthesia 10-15mins, 1.5-2hours s/t, nerve block 60mins. 
Prilocaine with epinephrine 1:200,000 pulpal anaesthesia 60-90mins, 3-8hours s/t
Less toxic than lidocaine
Can be used as topical with lidocaine. 

Don’t use in patients with idiopathic or congenital methamoglobinemia or patients taking acetaminophen

Question 20

What is methemoglobinemia?

Answer 20

It is a blood disorder in which an abnormal amount of methemoglobin (a form of haemoglobin) is produced.
Methemoglobin cannot release oxygen.

Question 21

Articaine (Brand name septanest, ubistesin)

Answer 21

Amide
Contains both amide linkage and Ester chain) more potent and lipid soluble. Short metabolic half-life.
Pot-1.5
Tox-0.6
Onset 1-5mins
Can cause methemoglobinemia and increased risk of mandibular paralysis.
Not for kids under 4y/o

Articaine 4% with epinephrine 1:100,000 pulp anaesthesia 60-70mins
Articaine 4% with epinephrine 1:200,000 pulpal anaesthesia 45-60mins

Question 22

Bupivicaine (Brand name marcaine)

Answer 22

Amide
Long duration
Chemically similar to mepivacaine but more lipid soluble = more potent
Tox- 4x less than lidocaine
Pot-4x more than lidocaine 
Onset - 6-10mins
Duration- 3-10hours

Bupivacaine 0.5% with epinephrine 1:200,000 pulpal anaesthesia 90-180mins, s/t 240-540 (good for full mouth reconstructions, implant surgery, extensive perio treatment and management of post op pain)

Not recommended for kids - biting!

Question 23

Types of syringes

Answer 23

• Non disposable
• Safety syringes
• Breech loading-aspirating syringe and self aspirating
• pressure syringes