Test One: LA And Fluoride Flashcards
What is the purpose of the benzene ring in the LA structure?
It is lipophilic which aids in crossing biological membranes
What is the difference between an amide and an ester linkage for local anesthetics?
Metabolism and clinical efficacy; esters metabolized in tissue/plasma by plasma cholinesterase making it easier to cleave and inactivate, also higher chance of allergy
Amides metabolized in Liver
Once inside the membranes how does the structure change?
Proton added to the tertiary amine at the other end to make it water soluble/polar
What is the mechanism of action of LAs?
Blocks action potentials by blocking sodium channels in the BH+ form
What is within a carpule of anesthesia?
Epinephrine, HCl or NaOH to adjust pH of solution, and metabisulfite (antioxidant to increase shelf life–cause of most allergies), isotonic NaCl
Theories for mode of action on sodium channels
Membrane expansion theory: Incorporation into the membrane closes pores/passage of electrolytes
Receptor mechanism: physical occlusion, allosteric change in conformation
alteration of electrical field
What phase of an action potential is affected by locals?
Phase 0-greatest influx of sodium ions; does not affect resting membrane potential
What is a differential nerve blockade?
Loss of autonomic influence by blocking temp sensation, pain, touch, pressure, and motor function
Why does cocaine not need epinephrine for vasoconstriction?
Cocaine prevents the reuptake of NTs which causes vasoconstriction
How does infection/inflammation affect locals?
Lower pH in tissue, increased blood flow promoting clearance, alteration in Na channel function and number, increased response to noxious stimulants
What processes do amides undergo during biotransformation?
Hepatic microsomal metabolism: Dealkylation and glucuronidation (any liver disease or decrease of hepatic circulation can cause systemic intolerance)
Why does articaine have a low risk of toxicity?
Its ester side chain is metabolized in plasma very quickly
How does renal clearance relate to protein binding capacity and pH of urine?
Inverse relationship with binding and inversely proportional to pH
What effect do LAs have on the heart and why?
They can cause decreased contractility. Bupivicaine is a highly lipophilic anesthetic and wants to affect excitable tissue like the myocardium- can be cardiotoxic
Most serious consequence of systemic LA toxicity?
postconvulsive central nervous system depression
What are some adverse effects of intravascular injection of a LA?
Cardio and resp depression, neuro damage and death
What is Clark’s rule for dosage?
Based on body weight. For a child: (weight in lbs. x adult dose)/ 150
What is the max dose for xylocaine/lidocaine?
With epi: 7 mg/kg or 500 mg
Without epi: 4.5 mg/kg or 300 mg
What is an adverse effect of prilocaine?
Methemoglobinemia: reduced capacity of hemoglobin to carry oxygen (also articaine and benzocaine)
Why is bupivicaine not recommended for children or disabled people?
More potent and maybe toxic than lido; prolonged effect and greater potential for soft tissue injury
What is a risk associated with 4% articaine and prilocaine?
Greater possibility of paresthesia
What is the reversal agent for LA effects?
Phentolamine mesylate (OraVerse): Alpha adrenergic blocker
What is epinephrine reversal?
Hypotension. This can be caused by antipsychotics like Prazosine which is an alpha1 blocker
EMLA
Eugenic mixture of local anesthetics; topical cream for skin–2.5% lidocaine and prilocaine
Oraqix
Intraoral preparation of EMLA- 50% pain reduction for srp
Probable toxic dose for fluoride?
5 mg/kg-minimum dose that could cause life threatening systemic signs/symptoms
Mechanism of action of fluoride
- inhibit enamel demineralization
- enhance enamel remineralization
- inhibit metabolism of carbs in cariogenic bacteria
Tx for acute fluoride toxicity
- prevent further absorption with gastric levage using fluid high in Ca like milk
- cardiopulmonary monitoring
- blood analysis
- iv infusion of salts like calcium gluconate as a buffer
- alkaline diuresis to promote excretion
Where and how does fluorosis (chronic toxicity) occur?
Excess ingestion of fluoride during development of teeth. Most commonly permanent canines and premolars and second molars. Once crowns are completely formed fluorosis is not possible.
Fluoride poisoning signs
Nausea, vomiting, diarrhea, can progress to hypotension, hypocalcemia, and hypomagnesemia and acidosis–>severe cardiac dysfunction
What concept is fluoridation of communal water supplies fulfilling?
Low concentration, high frequency
Optimal fluoride concentration in cold, cool, and warm climate areas
Cold- 1.2 ppm
Cooler- 1.0 ppm (60% of pop has access to this concentration)
Warmer- 0.6-0.8 ppm
What is the recommended fluoride concentration in schools and why is it different?
4.5 x higher than community because kids spend 1/4 of their time in school and they need to compensate for this lack of community exposure during these times
What does dosage of prescribed fluoride supplements depend on?
Age and existing fluoride concentration in water supply
What are the 3 fluoride formulations?
APF (acidulated phosphate fluoride), sodium fluoride, and stannous fluoride
Which formulation of fluoride is preferred?
APF
