9. Types of local anesthetics and their metabolism. Mechanism of action of local anesthetics. Vasoconstrictors. Interaction of local anesthetics with other drugs . Flashcards
Purpose of LA
-Pain control
Method of action of Local anaesthetics
- Block voltage gated sodium channels
- Block depolarisation of cell and inhibit neural activity
Structure of sodium channel
- Alpha 1 (pore through which sodium enters)
- Beta 1
- Beta 2
Number of variations of sodium channel
-9 different variations
Techniques of local Anaesthesia
- Topical
- Infiltration
- Regional block
- Intraosseous
- Intraligamentary
- Intrapulpal
Two types of local anaesthetics
- Esters
- Amines(mostly used)
Differences between esters and amines
- In metabolism and allergy production
- Esters metabolised in plasma
- Amines primarily undergo hepatic metabolism (prilocaine breakdown also in lungs, articaine metabolism in plasma)
Lidocaine
- Gold standard
- Plain solution of 2%-> short lasting
-Epinephrine vasoconstrictor common 1:200 000 to 1:80 000(5μg/m to 12.5μg/m)
Mepivicaine
-Concentration of 2% 1:100 000 epinephrine→ similar to 2% epinephrine lidocaine
3% plain (better anaesthesia than lidocaine when vasoconstrictor free solution required)
Prilocaine
- 4% plain solution
- 3% solution w/ vasocontrictor felypressin(if epinephrine free required)
Formulations of topical anesthetics
- Creams
- Ointments
- Sprays
Local anaesthetics agents commonly used as topical
- Lidocaine and Benzocaine
- Oraqix-Lidocaine and prilocaine
Technique for infiltration anaesthesia
- Mouth partly open
- Needle to depth of buccal sulcus(if bone contacted-slight withdrawal)
- Injection site supraperiosteal
- Aspiration and injection of 1-2 ml
Benefits of slow injection
- Reduces discomfort
- Increases success
- Lessens systemic problems
How long do infiltration injections last?
Pulps 45 mins and soft tissues 1.5-2 hours
Anaesthetic used in those allergic to amides
Procaine
Amide metabolised in plasma and therefore has shorter half life and is safer
Articaine
Articaine
4% 1:100 000 or 1:200 000 epinephrine
-Better mandibular infiltration anaesthesia than lidocaine
Bupivacaine
- long lasting
- 1:200 000
- Supplementary intraoral injection during general anaesthesia
- Reduces number of post-op analgesics required
Effect of Epinephrine in La
🔹Vasoconstriction
🔹Reduced bleeding
🔹Prolonged anaesthesia
Effects of Epinephrine injection into vessel
🔷Systemic absorption-systemic toxicity
🔹Cardiovascular effects- tachycardia , Hypertension, arrhythmias
🔹CNS effects- dizziness, tremors, seizures
🔹Local tissue ischemia->necrosis
Epinephrine effect on heart
🔹Secreted by adrenal glands
🔹Binds to beta adrenergic receptors on heart muscle cells
🔹Increases HR and strength of contractions->increased blood supply
🔹Raises Bp
Role of epinephrine in allergic reactions
🔸Inhibits release of inflammatory mediators
🔸Histamine, leukotrienes
How epinephrine counteracts effects of vasodilation and increased vascular permeability during allergic reactions
🔸Induces vasoconstriction and reduces vascular permeability
Importance of bronchodilation during severe allergic reactions
🔸Improved airflow
Effects epinephrine has on cardiovascular system during allergic reactions
🔸Maintains blood pressure and cardiac output
How Articaine has better penetration into tissues than lidocaine
🔸Presence of ester group in its structure
🔸Allows better diffusion
Advantages of Articaines improved penetration
🔸More profound anaesthesia at lower doses
Main effects of epinephrine in allergy
🔸Vasoconstriction (reduces swelling)
🔸Bronchodilation (improved airflow)
🔸Cardiovascular effects
🔸Suppression of inflammatory mediators
Active ingredient of Ubistein
Articaine and epinephrine
Active ingredient of Scandonest
Mepivicaine and epinephrine
Active ingredient of xylodren
Lidocaine and epinephrine
Active ingredient of dentocain
Articaine and adrenaline
Active ingredient of septonest
Adrenaline and Articaine
Factors that affect intensity and duration of LA’s
🔸Tissue blood flow
🔸Activity of plasma cholinesterase
🔸Vasoconstrictor use
🔸pH of tissue
🔸Dose of La
How infection hinders effect of La
🔸Creates acidic environment->decreases pH of tissues
🔸Alters ionisation and ability to penetrate nerve fibres->
🔸Reduces the potency and duration of LAs
Strategies to overcome resistance of LA in infected tissues
🔸Antibiotics and anti inflammatory agents (reduce inflammation and acidity)
🔸Regional nerve blocks and intravenous sedation
Overdose of LAs can cause
🔹Severe hypotension (Vasodilation)
🔹Seizures
🔹Respiratory depression
