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Properties of the Ideal Local Anesthetic:

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Potent. Reversible. Absence of local and systemic reactions. Absence of allergic reactions. Rapid onset and satisfactory duration. Adequate tissue penetration. Low cost. Stability in solution. Ease of metabolism and excretion.

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Two major groups of L.A.:

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Amides and Esters.

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Where are amides metabolized?

answer

the liver.

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Where are esters metabolized?

answer

the blood plasma.

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Amides and allergies:

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very low allergy potential; uncommon.

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Esters and allergies:

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high allergy potential; used as a topical.

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Examples of amides:

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lidocaine which is Xylocaine. mepivicaine which is Carbocaine. bupivacaine which is Marcaine. prilocaine which is Citanest. articaine which is Septocaine.

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Examples of esters:

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procaine which is Novocain. ethylaminobenzoate which is 20% Benzocaine.

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What is the most commonly used anesthetic solution in dentistry?

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Lidocaine which is Xylocaine. Lidocaine 2% w/ 1:100,000 epinephrine.

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Is lidocaine/xylocaine safe for pregnancy?

answer

Yes.

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There are currently no ____ avaliable in a dental cartridge today.

answer

esters.

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Is Lidocaine 2% w/ 1:100,000 epinephrine a vasodilator or vasoconstrictor?

answer

vasoconstrictor.

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What does Lidocaine 2% w/ 1:100,000 epinephrine provide?

answer

profound anes. of medium duration.

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A patient who has an allergy to one agent in a group is more likely to exhibit a hypersensitivity reaction to:

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other agents within the same group.

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If an allergic reaction does occur, most likely it is toward the:

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*preservatives.

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Cross-hypersensitivity between the amides and the esters is:

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very unlikely.

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Nerve conduction or nerve action potential involves:

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opening both Na+ and K+ channels. Na+ in and K+ out.

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Local anesthetics block nerve impulse travel by blocking the:

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depolarization (pain sensation) process.

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What does local anesthetics attach themselves to?

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specific receptors in the nerve cell membrane.

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Local anesthetics reduce:

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Na+ permeability.

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What is reducing Na permeability?

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blocking Na from entering cell.

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What does reducing Na permeability allow?

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the flow of K+ out of the cell, thus inhibiting membrane repolarization (action potential) and nerve conduction.

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What is local anesthetics mechanism of action? How does it work?

answer

Work by blocking peripheral nerve conduction by decreasing the permeability of ion channels to sodium; local anesthetic agents inhibit the influx of sodium ions (Na+) by competing with calcium (Ca++) for binding sites.

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Local anes. agents decrease the: prolong the:

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DEcrease the rate of DEpolarization. prolong rate of repolarization.

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Local anesthetics are weak bases occurring equilibrated between their two forms:

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the fat soluble - free base and water-soluble hydrochloride salt.

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The portion of drug in each form is determined by the:

answer

pKa of the local anesthetic and the pH of the environment.

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pKa=

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pH at which half is salt and half is base.

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Once injected into local tissue, the amount of local anesthetic in the free base form increases and allows

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for greater tissue penetration.

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If there is an infection or inflammation, the free base form decreases and:

answer

less drug penetrates the tissue.

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Local anesthetic antioxidant:

answer

Sodium metabisulfite or sodium bisulfite.

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Sodium metabisulfite or sodium bisulfite; present if anesthetic contains:

answer

a vasoconstrictor.

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Asthmatic pts. who are injected with _______ + ______ need to be watched for signs of wheezing and chest tightness!

answer

vascoconstrictors + sulfite agent.

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Absorption:

answer

Uptake into circulatory system.

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Absorption factors:

answer

route of injection. tissue vascularity.

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Tissue vascularity is a function of inflammation, vasodilating properties of the local anesthetic, presence of heat, or the use of massage

answer

...

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It is important to reduce the systemic absorption of a local anesthetic when it is used in dentistry This is done by the addition of:

answer

a vasoconstrictor.

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Pharmacokinetics: in short, l.a's are absorbed from their site of administration into the bloodstream, which:

answer

dilutes and carries them to all parts of the body.

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Distribution:

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Into the tissue. Dissemination throughout the body.

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The local anesthetic becomes partially bound to:

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plasma and red blood cells.

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The unbound drug freely diffuses to:

answer

other tissues including the CNS and across the placenta.

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METABOLISM: Biotransformation in:

answer

liver.

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EXCRETION by:

answer

the kidneys.

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*Amides are primarily removed from the blood and inactivated in:

answer

the liver.

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In severe liver disease, or with alcoholism, amides may:

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accumulate and produce systemic toxicity.

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*Esters are metabolized in the:

answer

blood plasma.

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*The main pharmacologic effect of local dental anesthetic is to:

answer

reversibly block peripheral nerve conduction.

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Local anesthetic (lidocaine) are also useful intravenously in the treatment of:

answer

arrhythmias.

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Adverse reactions are directly related to:

answer

blood levels.

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Factors that influence toxicity:

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Drug itself Concentration. Route of administration. Rate of injection. Vascularity. Patient's weight. Rate of metabolism and excretion.

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Systemic Effects:

answer

Most affected are CNS and CVS.

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CNS stimulation may occur:

answer

first.

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CNS stimulation may occur first; results in:

answer

restlessness, tachycardia and tremors.

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CNS depression follows:

answer

CNS stimulation.

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CNS depression leads to:

answer

leading to respiratory and CV collapse.

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Local anesthetic can produce myocardial depression and cardiac arrest with:

answer

peripheral vasodilation.

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Local effects of local anesthetic include physical injury; such as:

answer

hematoma caused by poor injection technique.

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Hematomas occur most often with:

answer

PSAs.

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If patient has a sulfite allergy, local anesthetic with vasoconstrictors may cause:

answer

an asthma attack.

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If a patient has a sulfite allergy; local anes. w vasoconstrictors contain a sodium bisulfite that serves as an antioxidant. Therefore what should be used?

answer

plain without EPI. is the aneshetic of choice.

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What is a hematoma?

answer

collection of blood outside the blood vessels.

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Isotonic:

answer

Having the same or equal osmotic pressure.

question

Local Anesthetic Solution:

answer

vasoconstrictor, antioxidant (sodium bisulfite), sodium hydroxide, sodium chloride.

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Vasoconstrictor:

answer

Reduces blood supply to the area; retards absorption; reduces systemic toxicity; prolongs the duration of action.

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Antioxidant: Sodium bisulfite:

answer

preservative that delays the oxidation of epinephrine and prolongs shelf life.

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Sodium hydroxide:

answer

Adjusts the pH of the solution to between 6 and 7.

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Sodium chloride:

answer

Makes the injectable solution isotonic.

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Choice of agent should be based upon:

answer

onset of action, duration of anesthesia required and side effects.

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The amides: (the fab 5)

answer

lidocaine, brand name- Xylocaine. mepivicaine, brand name- Carbocaine. prilocaine, brand name- Citanest. bupivacaine, brand name- Marcaine. articaine, brand name- Septocaine.

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Most commonly used anesthetic:

answer

*Lidocaine with epinephrine 1:100,000.

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Some patients experience ____ with lidocaine.

answer

sedation.

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In toxic reactions (to lidocaine) one is likely to observe:

answer

observe CNS depression initially rather than CNS stimulation characteristic of other local anesthetic solutions.

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Lidocaine (xylocaine) toxic reaction side effects:

answer

Hypotension. Headache. Shivering.

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mepivicaine's rate of onset, duration, potency, toxicity similar to:

answer

lidocaine.

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mepivicaine can be used as:

answer

as a 3% solution without a vasconstrictor ("plain") for short procedures when a vasoconstrictor is contraindicated.

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Caution should be used with mepivicaine because:

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toxicity is more likely because of the increased concentration of local anesthetic with out vasoconstrictor.

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Benefit of a shorter duration does not usually warrant elimination of the vasoconstrictor; especially when:

answer

concentration of anesthetic is increased.

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prilocaine:

answer

less potent, less toxic than lidocaine with a slightly longer duration of action.

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Disadvantage of prilocaine:

answer

it may induce methemoglobinemia.

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Methemoglobinemia:

answer

condition in which iron in hemoglobin does not carry O2 effectively, therefore, this anesthetic should not be used with oxygentation problems in patients.

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Potential advantage of prilocaine;

answer

that the concentration of EPI (1:200,000) is ½ that of lidocaine with EPI (1:100,000).

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bupivacaine advantage:

answer

greatly prolongs duration of action, good for ≥1.5 hours of anesthesia, or when post-op pain is expected; like with oral or periodontal surgery. longest duration.

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articaine (Septocaine) requires:

answer

a lower dose and this anesthetic possess some concern with an increased risk for paraesthesia. Longer duration than prilocaine and shorter duration than bupivacaine.

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articaine (Septocaine):

answer

Widely used in most countries. Greater lipid solubility; thus ability to cross nerve membranes; this allows for more rapid reinjection, if needed, thus, in toxicity risk. Rapidly metabolized. (short half-life). In a 4% solution with 1:100,000 epi; can only safely use one-half as much as 2% lidocaine.

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Vasoconstrictors are also called:

answer

adrenergic agonists or sympathomimetics.

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Reasons vasoconstrictors/epinephrine:

answer

1. Prolong the duration of action. 2. Increase the depth of anesthesia. (by retaining the solution in the treatment area). 3. Reduce toxicity by delaying systemic absorption . 4. Reduce bleeding; localized hemostasis.

question

How do vasoconstrictors reduce bleeding (localized hemostasis)?

answer

by decreasing blood flow to the area due to constriction of blood vessels.

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Epinephrine is used for:

answer

Management of acute allergic reactions. Management of bronchospasm. Management of cardiac arrest. Hemostasis. Produce mydriasis which is dilation of pupils.

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Epinephrine used in local dental anesthetics to:

answer

decrease absorption into the CV system. increase depth of anesthesia. increase duration of anesthesia.

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Contraindications to Epinephrine:

answer

Heart attack, MI or stroke in the last six months. Uncontrolled hypertension (≥ 200/115), angina, arrhythmias. Uncontrolled severe hyperthyroidism. Uncontrolled diabetes.

question

The majority of cardiovascular patients should _____ from the use of EPI.

answer

benefit.

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CV patients who are ______ (____ or ____) may receive local dental anesthesia with EPI.

answer

controlled. (ASA II or ASA III).

question

Patients with cardiovascular disease, who can receive a vasoconstrictor, should receive:

answer

the lowest dose possible.

question

Dose of epi for a healthy patient:

answer

.2mg

question

Dose of epi for a cardiac patient:

answer

0.04mg

question

*Cardiac Dose:

answer

A cardiac patient could be given two (2) cartridges of lidocaine with 1:100,000 epi without exceeding the cardiac dose.

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Esters such as benzocaine (20%) are commonly used:

answer

topically.

question

Most commonly topical:

answer

benzocaine 20%.

question

Examples of benzocaine:

answer

hurricaine, anbesol, benzodent, orabase-B.

question

2nd most common topical:

answer

lidocaine, an amide.

question

Possible reactions to benzocaine:

answer

burning, stinging, hypersensitivity.

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Avoid unmetered sprays which may be:

answer

overly absorbed into the CV system.

question

Dentipatch:

answer

Anesthetic occurs within 2.5 mins. Duration:15 minutes of application period. Persists: approximately 30 minutes after removal.

question

Dentipatch is best used on:

answer

Maxillary arch. On the mandibular arch it slides around per saliva.

question

Intranasal Anesthetics:

answer

lidocaine. used currently on pets. may be used on humans in the future.

question

Oraverse is an injection given by: what is it?

answer

the dentist only. it is a dental anesthesia reversal inhection.

Chapter 9: Local Anesthetics – Flashcards

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