Pre-administration Protocol

Before administrating any drug to a patient, the clinician must evaluate the health of the patient to determine whether the patient can tolerate the drug and minimize possible complications resulting from the drug interacting with the patient’s organ systems or with medication the patient is taking. Local anaesthetic actions include depressant effects on the central nervous system and cardiovascular system. Because local anaesthetics undergo bio-transformation in the liver (amides) and blood (esters) and are excreted by the kidneys, the status of these organ systems should be evaluated. A patient’s psychological acceptance of a local anaesthetic needs to be assessed as many patients view the “shot” as the most traumatic aspect of the dental procedure.

While a comprehensive medical history is recommended for all dental patients, the following questions are most pertinent for those patients who are to receive local anaesthesia.

  • Has the patient ever received a local/topical anaesthetic for medical or dental care?
    • If so, were there any adverse reactions?
  • Is the patient having any pain at this time?
    • How severe?
    • How long?
    • Any swelling?
  • Is the patient nervous about receiving dental treatment?
    • Why are they nervous?
    • Has the patient had any bad dental experiences?
  • Has the patient been in a hospital during the past two years?
  • Has the patient taken any medicine or drugs during the past two years?
  • Has the patient been under the care of a physician during the past two years?
  • Is the patient allergic to any foods or drugs?
  • Does the patient have any bleeding problems that require special treatment?
  • Has the patient ever have any of the following conditions or treatment?
    • Heart failure
    • Heart attack or heart disease
    • Angina pectoris
    • Hypertension
    • Heart murmur, rheumatic fever
    • Congenital heart problems
    • Artificial heart valve
    • Heart pacemaker
    • Implanted cardioverter/defibrillator
    • Heart operation
  • Has the patient ever have any of the following conditions or treatment?
    • Anemia (methemoglobinemia)
    • Stroke
    • Kidney trouble
    • Hay fever, sinus trouble, allergies or hives
    • Thyroid disease
    • Pain in jaw joints
    • HIV/AIDS
    • Hepatitis A, B, C
    • Epilepsy or seizures
    • Fainting, dizzy spells, nervousness
    • Psychiatric treatment
  • Does the patient bruise easily?
  • Is the patient pregnant?
  • Does the patient have any disease, condition or problem not mentioned?

As the confines of this course limit a full discussion of the effects of local anaesthetics on the body and with other drugs the following tables summarize the more common interactions.

Table 6. Drug-to-Drug Interactions.5
Drugs Example Significance Rating Interaction
Summation interactions of local anaesthetics Lidocaine plus articaine Major Toxicity of local anaesthetics are additive. Total dose of all administered local anaesthetics should not exceed the maximum recommended dose of the drugs.
Local anaesthetics with opioid sedation Local anaesthetic with Demerol Major May increase the risk of local anaesthetic overdose. Minimize the dosage of the local anaesthetic.
Vasoconstrictor with cocaine Epinephrine with cocaine

Vasopressors should not be administered to patients who have used cocaine within the last 24 hours
Major Increases likelihood of cardiac dysrhythmias, tachycardia and hypertension. May lead to MI and cardiac arrest.
Vasoconstrictors with general anaesthetics Epinephrine with halothane Major Increases the likelihood of cardiac dysrhythmias. Discuss with cardiologist before administration.
Vasoconstrictors with nonselective beta adrenoreceptor antagonists (beta-blocker) Epinephrine with propranolol Major TCAs enhance the cardiovascular actions of administered vasopressors.

5-10X with levonordefrin and norepinephrine.

2X with epinephrine
Local anaesthetic induced methoglobinemia (a condition in which the oxygen carrying capacity of the blood is reduced) Excessive doses of prilocaine Moderate Large doses of benzocaine can also induce methoglobinemia
Vasoconstrictor with antipsychotic drugs Epinephrine with chlorpromazine Moderate May result in hypotension
Vasoconstrictor with thyroid hormone Epinephrine with thyroxine Moderate Increase in effects of vasoconstrictor with excessive thyroid hormones
Sulfonamides and esters Procaine and tetracaine and sulfonamides Minor Ester anaesthetics inhibit the bacteriostatic action of sulfonamides. Use amide local anaesthetics.
Amide local anaesthetics with metabolic inhibitors (GI disorders) Cimetidine (Tagamet) and lidocaine. No problem with rantidine (Zantac) and famotidine (Pepcid) Minor Inhibits anaesthetic bio-transformation. Increases half-life of anaesthetic.

Use minimal dose of amide local anaesthetic.
Significance Rating
Major – Potentially life threatening or capable of causing permanent damage.
Moderate – Could cause deterioration of patient's clinical status; additional treatment or hospitalization might be necessary.
Minor – Mild effects that are bothersome or unnoticed; should not significantly affect therapeutic outcome.
Table 5. Contraindications for Local Anaesthetics.3
Medical Problem Drugs to Avoid Type of Contraindication Alternative Drug
Local anaesthetic allergy, documented All local anaesthetics in the same class, (e.g., esters) Absolute Local anaesthetics in a different chemical class (e.g., amides)
Bisulfite allergy Local anaesthetics containing a vasoconstrictor Absolute Local anaesthesia without a vasoconstrictor
Atypical plasma cholinesterase Esters Relative Amides
Methoglobinemia, idiopathic or congenital Articaine, prilocaine, topical benzocaine in children younger than 2 years Relative Other amides or esters
Significant liver dysfunction (ASA III-IV) Amides Relative Amides or esters but judiciously
Significant renal dysfunction (ASA III-IV) Amides or ester Relative Amides or esters but judiciously
Significant cardiovascular dysfunction (ASA III-IV) High concentrations of vasoconstrictors (as in racemic epinephrine cords) Relative Local anaesthetics with concentrations of 1:200,000 or 1:100,000 or mepivacaine 3% or prilocaine 4% (nerve blocks)
Clinical hyperthyroidism (ASA III-IV) High concentrations of vasoconstrictors (as in racemic epinephrine cords) Relative Local anaesthetics with concentrations of 1:200,000 or 1:100,000 or mepivacaine 3% or prilocaine 4% (nerve blocks)
Absolute contraindication – Implies that under no circumstance should this drug be administered to this patient because the possibility of potentially toxic or lethal interactions is increased.
Relative contraindication – Implies that the drug in question may be administered to the patient after carefully weighing the risk of using the drug to its potential benefit, and if an acceptable alternative drug is not available.
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