Articaine Overview: Properties and Metabolism

Articaine

• Hybrid molecule, classified as an amide, but with ester characteristics
• 1.5 times more potent than lidocaine
• Toxicity similar to lidocaine and procaine
• Metabolism:
  • Only amide local anesthetic with a thiophene group (enhances lipid solubility and tissue penertration)
  • Biotransformation occurs in plasma via hydrolysis by plasma esterase and in liver via hepatic microsomal enzymes
• Excretion:
  • Via the kidneys; 5% to 10% unchanged, 90% metabolites
• Vasodilating Properties:
  • Vasodilating effect equal to that of lidocaine
• Effective dental concentration: 4%
• Onset of action:
  • Infiltration: 1 to 2 minutes
  • Block: 2 to 3 minutes
• Pulpal anesthesia:
  • 1:100,000 epinephrine: 60 – 75 minutes
  • 1:200,000 epinephrine: 45– 60 minutes
• Soft tissue anesthesia:
  • 1:100,000 epinephrine: 180 -360 minutes (3-6 hours)
  • 1:200,000 epinephrine: 120-300 minutes (2-5 hours)
• Maximum recommended dose: 7.0 mg/kg body weight
• Pregnancy classification: C (not safe)
• Side effect: Methemoglobinemia
• Contraindications:
  • Idiopathic or congenital methemoglobinemia
  • Cardiac & respiratory failure
  • Allergy to sulfite - containing drugs

Bupivacaine

• Classification: Amide
• Long acting local anesthetic drug
• Bupivacaine HCl 0.5% + epinephrine 1:100,000 or 1:200,000
• Potency: 4 times that of Lidocaine
• Pregnancy classification: C (not safe)
• Indications:
  • Lengthy dental procedures (Oral Surgery, implant surgery, periodontal procedures)
  • Management of postoperative pain
• Contraindications:
  • Physically & mentally disabled children
  • Patients with cardiovascular issues

Topical Anesthetics

• Intact skin is a barrier to diffusion of local anesthetics
• Mucous membranes and injured skin lack this barrier which allows for penetration
• Topical anesthesia is effective only on surface tissues (2 to 3mm)
• To increase efficacy, a more concentrated form is used (5% or 10% lidocaine)
• Commonly used topical local anesthetics: benzocaine, dyclonine hydrochloride, EMLA, lidocaine
• Benzocaine 20%:
  • Ester local anesthetic
  • Poorly soluble in water, remains at the site of application longer, providing a prolonged duration of action
  • Not suitable for injection
• Dyclonine Hydrochloride:
  • Ketone derivative without an ester or amide linkage
  • Can be used in patients that are allergic to common anesthetics
• EMLA (Eutectic Mixture of Local Anesthetics):
  • 2.5% Lidocaine + 2.5% Prilocaine
  • Emulsion of lidocaine and prilocaine in a 1:1 ratio by weight
  • Works on intact skin
  • Applied 1 hour prior to procedure
  • Contraindications:
    • Congenital or idiopathic methemoglobinemia (Prilocaine)
    • Infants younger than 12 months receiving treatment with methemoglobin inducing agents
    • Known sensitivity to amide type local anesthetics

Selection of Local Anesthetic for a Patient

• Length of time pain control is necessary
• Potential need for post treatment pain control
• Possibility of self-mutilation (self harm) in the post operative period
• Requirement for hemostasis
• Presence of any contraindications (Medical History, Allergies, Pregnancy)

Vasoconstrictors

• Classification:
  • Based on chemical structure:
    • Catecholamines: Epinephrine, Norepinephrine, Levonordefrin, Isoproterenol, Dopamine
    • Noncatecholamines: Amphetamine, Methamphetamine, Ephedrine, Hydroxyamphetamine, Metaraminol, Methoxamine, Phenylephrine
  • Based on mode of action:
    • Directly Acting: Epinephrine, Norepinephrine, Levonordefrin, Isoproterenol, Dopamine, Methoxamine, Phenylephrine
    • Indirectly Acting: Amphetamine, Methamphetamine, Hydroxyamphetamine, Tyramine
    • Mixed Acting: Metaraminol, Ephedrine

Action of Vasoconstrictors

• Decrease blood flow
• Decreased rate of absorption of LA into CVS, lower anesthetic blood levels
• Decrease the risk of toxicity
• Increases duration of action
• Decrease bleeding (hemostasis)

Adrenergic Receptors

• Special proteins found on the surface of cells, act as docking stations for catecholamines (Epinephrine)
• Two types of receptors:
  • Alpha (α) - vasoconstriction
  • Beta (β) - vasodilation, bronchodilation, cardiac stimulation

Epinephrine

• Mode of action: Acts directly on alpha (α) and beta (β) adrenergic receptors
• Systemic Effects:
  • Myocardium: ↑ heart rate & cardiac output
  • Blood Pressure: ↑ systolic pressure
  • Vasculature: vasoconstriction of smaller arterioles
  • Respiratory: Bronchodilator
  • CNS: Not a potent CNS stimulant
  • Metabolism:
    • Increase oxygen consumption
    • Glycogenolysis - ↑ blood sugar
• Clinical applications:
  • Management of acute allergic reactions (anaphylaxis)
  • Management of refractory bronchospasm (status asthmaticus)
  • Management of cardiac arrest
  • As a vasoconstrictor in local anesthetics
  • To produce mydriasis (dilatation of the pupil)

Epinephrine Recommended Maximum Dosages:

• Normal healthy patient (ASA I):
  • 1:50000 (36): 5.5 cartridges
  • 1:100000 (18): 11 cartridges
  • 1:200000 (9): 22 cartridges
• Patient with clinically significant CVS disease (ASA III or IV):

  • 1:50000 (36): 1 cartridges

  • 1:100000 (18): 2 cartridges

  • 1:200000 (9): 4 cartridges

  • Maximum epinephrine dose of 0.2 mg (200 µg) per appointment for normal healthy patients (11 cartridges)

  • Maximum epinephrine dose of 0.04 mg (40 µg) per appointment for ASA III or ASA IV (2 cartridges)

Levonordefrin

• Mode of Action:
  • Direct α-receptor stimulation (75%), with some β activity (25%)
  • 15% as potent a vasopressor as epinephrine
• Systemic Actions:
  • Produces less cardiac and CNS stimulation than epinephrine
• Side Effects and Overdose:
  • The same as with epinephrine but to a lesser extent
  • Higher doses can cause: hypertension, ventricular tachycardia, and anginal episodes in patients with coronary artery insufficiency
• Clinical Applications:
  • Used as a vasoconstrictor in local anesthetics
  • Combined with Mepivacaine in a 1:20,000 dilution
• Maximum Doses:
  • 1 mg per appointment for all patients of a 1:20,000 dilution (11 cartridges)
  • Volume is limited by local anesthetic dose

Selection of Vasoconstrictors

• Length of the dental procedure
• Need for hemostasis
• Requirement for postoperative pain control
• Medical status of the patient

Contraindications of Vasoconstrictors

• Benefits and risks of including the vasopressor must be weighed against using a plain solution
• Groups of patients with contraindications include:
  • Patients with more significant cardiovascular disease (ASA class 3 and 4)
  • Patients with certain non-cardiovascular diseases (e.g., thyroid dysfunction, diabetes, sulfite sensitivity)
  • Patients receiving MAO inhibitors (monoamine oxidase inhibitors)

How to calculate the maximum number of carpules (cartridges) per appointment

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

This quiz covers the key characteristics and pharmacology of Articaine, including its potency compared to other local anesthetics, metabolic pathways, and clinical application in dental procedures. Test your understanding of its properties, efficacy, and safety parameters.