Local Anesthetics Overview

Articaine

• Articaine is classified as an amide, but it possesses both amide and ester characteristics
• It is 1.5 times more potent than lidocaine
• Toxicity is comparable to lidocaine and procaine
• It is the only amide-type local anesthetic that contains a thiophene group, which enhances its lipid solubility and penetration into tissues
• Metabolises in plasma (hydrolysis by plasma esterase) and liver (hepatic microsomal enzymes)
• Excretion via kidneys, approximately 5% to 10% unchanged
• Vasodilating effects similar to lidocaine

Bupivacaine

• Classified as an Amide
• Long-acting local anesthetic
• Potency is 4 times greater than lidocaine
• Indicated for lengthy dental procedures (oral surgery, implant surgery, periodontal procedures)
• Used to manage postoperative pain

Topical Anesthetics

• Intact skin prevents local anesthetic diffusion
• Mucous membranes and injured skin allow topical anesthetics to reach nerve endings
• Topical anesthesia is effective only on surface tissues (2 to 3 mm deep)
• More concentrated forms of the drug are used topically (5% or 10% lidocaine) than for injection (2% Lidocaine)
• Common topical anesthetics include: benzocaine, dyclonine hydrochloride, EMLA, lidocaine
• Benzocaine 20% is poorly soluble in water, remains at the site of application longer, providing a prolonged duration of action, not suitable for injection
• Dyclonine Hydrochloride is classified as a ketone derivative and can be used in patients allergic to common anesthetics

EMLA

• EMLA cream contains 2.5% Lidocaine + 2.5% Prilocaine
• Emulsion where oil phase is a eutectic mixture of lidocaine and prilocaine
• Works on intact skin
• Applied 1 hour prior to procedure

Vasoconstrictors

• Vasoconstrictors decrease blood flow and the rate of local anesthetic absorption into the cardiovascular system, lowering anesthetic blood levels
• Reduce risk of toxicity, increase duration of action, and promote hemostasis (decrease bleeding)
• Alpha (α) receptors cause vasoconstriction, beta (β) receptors promote vasodilation and bronchodilation
• Epinephrine directly activates both alpha (α) and Beta (β) adrenergic receptors
• Levonordefrin primarily activates alpha receptors

Epinephrine

• Increases heart rate and cardiac output
• Increases systolic blood pressure
• Causes vasoconstriction of smaller arterioles
• Acts as a bronchodilator
• Increases oxygen consumption and glycogenolysis (increasing blood sugar)

Levonordefrin

• Less potent than epinephrine
• Less cardiac and CNS stimulation compared to epinephrine

Selecting a Local Anesthetic

• Consider the duration of pain control needed
• Assess the potential for post-treatment pain
• Consider the risk of self-harm
• Evaluate the need for hemostasis
• Review contraindications (medical history, allergies, pregnancy)

Selecting a Vasoconstrictor

• Consider the length of the dental procedure
• Assess the need for hemostasis during and after the procedure
• Evaluate the requirement for post-operative pain control
• Review the medical status of the patient
• Benefits and risks of vasoconstrictors must be weighed against benefits and risks of using a plain anesthetic solution

Contraindications for Vasoconstrictors

• Individuals with significant cardiovascular disease (ASA classes 3 and 4)
• Patients with certain non-cardiovascular diseases (thyroid dysfunction, diabetes, sulfite sensitivity)
• Patients receiving MAO inhibitors (monoamine oxidase inhibitors)

Calculating Cartridge Maximums

• 2% Mepivacaine with Epi 1:100,000 (red color): Maximum carpules/visit = (Body weight X 6.6mg/kg) / 36 mg/cartridge (36 mg/cartridge calculated from 20 mg mepivacaine/ml X 1.8 ml/cartridge)
• 3% Mepivacaine without Epi (green color): Maximum carpules/visit = (Body weight X 6.6mg/kg) / 54 mg/cartridge (54mg/cartridge calculated from 30 mg mepivacaine/ml X 1.8 ml/cartridge)
• 4% Articaine with Epi (blue color): Maximum carpules/visit = (Body weight X 7 mg/kg) / 72 mg/cartridge