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Questions and Answers
What is a common application for benzocaine?
Which type of local anesthetic is more commonly used due to its stability and low risk of hypersensitivity reactions?
What is the half-life of lignocaine?
Which local anesthetic is least likely to cause an allergic reaction among those listed?
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What is a significant risk associated with the use of high concentrations of benzocaine?
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Why is procaine generally not preferred for dental procedures?
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Which local anesthetic is likely to be a better choice for someone with pseudocholinesterase deficiency?
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Which characteristic is true for ester local anesthetics?
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What is the onset time for Xylocaine 5% Ointment?
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How long does the effect of Xylocaine 5% Ointment typically last?
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Which of the following statements about Oraqix is true?
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What is the active ingredients composition of Oraqix?
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What is the safe administration route for Oraqix?
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Which of the following local anesthetics is used without adrenaline?
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What is a key characteristic of Oraqix regarding its physical properties?
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What is a disadvantage of using Xylocaine 5% Ointment?
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How does the addition of sodium metabisulfite to a local anesthetic affect the solution?
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What is the primary reason vasoconstrictors are added to local anesthetics?
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Which statement about amide local anesthetics is true?
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What is the effect of lowering the pH in local anesthetic solutions?
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What role does sodium chloride play in local anesthetic solutions?
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Why might a dentist choose to administer local anesthesia without a vasoconstrictor?
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What is one significant consequence of the addition of adrenalin to local anesthetic solutions?
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What is the effect on patient experience when the pH of a local anesthetic solution is unaltered?
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Study Notes
Topical Anaesthetic Agents
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Topical anaesthetic agents are categorized by their intermediate chains: Esters (one 'i' in the name) and Amides (two 'i's in the name).
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Esters are less common but are used for topical application in some cases.
Ester Anaesthetics
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Procaine (brand name Novocaine) was introduced in 1905.
- Slow onset (6-10 minutes) due to high pKa.
- Short duration (60 minutes) due to rapid metabolism by pseudocholinesterase in plasma (98%).
- High dose (10 mg/kg) is possible due to short half-life.
- Vasodilating properties.
- Hypersensitivity reactions to inactive metabolite para-aminobenzoate (PABA) are a common problem.
- Pseudocholinesterase deficiency (affecting 1 in 2800-3000 people) can lead to abnormally slow metabolism and risk of methemoglobinemia.
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Benzocaine is used for topical application.
- Found in sore throat lozenges, mouthwash, throat spray, gel, and paste.
- Can also be used for earache and sunburn.
- Overuse of high concentrations can cause methemoglobinemia.
Amide Anaesthetics (Most Common in Dentistry)
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Lignocaine
- 2% plain or with adrenaline (27.5 mcg).
- Half-life of 1.5-1.8 hours.
- Lignospan Special is another brand name.
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Articaine
- 4%.
- 1:100,000 adrenaline.
- Half-life of 1.8 hours (slight longer than Lignocaine).
- Septanest is another brand name.
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Prilocaine
- 2.2ml or 1.8ml cartridges.
- 3% with or without felypressin (vasoconstrictor).
- Half-life is similar to Lignocaine.
- Citanest is another brand name.
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Oraqix
- Gel containing Lignocaine (25mg/g) and Prilocaine (25mg/g).
- Applied to periodontal sulcus prior to scaling/cleaning for 30-second onset.
- Duration of action is 17-20 minutes.
Factors Affecting Local Anaesthetic Efficacy
- pH is a critical factor influencing the burning sensation of local anaesthetics.
Common Additives to Local Anaesthetic Solutions
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Antioxidants (commonly sodium metabisulfite)
- Protects vasoconstrictor from oxidation.
- Lowers pH, leading to slower onset and increased burning during injection.
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Sodium Chloride
- Used to adjust the solution to become isotonic.
Vasoconstrictors
- All amide local anaesthetics are vasodilators.
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Vasoconstrictors are added to counter vasoconstriction.
- Slow local absorption of the drug, increasing duration of action and reducing toxicity.
Topical Anaesthetic Applications in Dentistry
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5% Lignocaine Ointment
- Adheres to dry mucosa.
- Onset of action in 3-5 minutes.
- Duration of action of 15-20 minutes.
- Does not work on intact skin.
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Description
Explore the classification and characteristics of topical anaesthetic agents, focusing on Esters and Amides. Learn about Procaine and Benzocaine, their properties, uses, and associated risks. This quiz is essential for understanding the implications of these agents in medical applications.
