Anesthetic Agents Part 1 Flashcards
How do we classify local anesthetics?
- By their chemical structure
- esters
- amides - Duration of pulpal and hard tissue anesthesia
- short –> 20-40 minutes
- intermediate –> up to 70 minutes
- long –> up to 8 hours
In U.S. we only inject which LA
Amide local anesthetics in dentistry
- injectable ester LA are available in other countries
Where do we use ester anesthetics?
In topical anesthetics
What are the considerations for selecting a local anesthetic agent
- length of time for which pain control is necessary
- need for post-treatment pain control
- need for hemostasis
- presence of contraindications for a given drug
What factors affect both the depth and the duration of a drug’s action
- individual response to drug
- accuracy in drug administration
- status of the tissues (ph)
- anatomical variation
- type of injection (supraperiosteal/infiltration or block)
Describe the difference between a hyper-responder and hypo-responder to LA
Hyper - effect lasts beyond what is expect
Hypo - effect dissipates quickly
T or F, Hypo-response to LA is not attributed to biotransformation/elimination
True –> not related to clinical actions
- simply occurs because this is how this individual responds to this drug
T or F, Deposition further away from nerve provides lesser depth and duration
True - “deposition closer to nerve provides greater depth and duration”
How does inflammation affect depth and duration of anesthesia?
Inflammation, infection or pain usually decreases depth and anticipated duration of anesthesia
How does increased vascularity affect duration of anesthesia?
Increased vascularity at site of deposition results in more rapid absorption and decreased duration
- depth of anesthesia will be greater in less vascular regions
T or F, Smaller than usual volumes decrease duration
True
T or F, Larger than recommended doses increase duration
False, DO NOT increase duration
Which duration of drug is best suited for non-traumatic procedures
Drugs with short duration
Name the drugs with long duration
bupivacaine (.5%) (8-12 hour of soft tissue anesthesia)
prilocaine 4% with 1:200,000 epinephrine (5-8 hours of soft tissue anesthesia)
Name the drugs with short duration
mepivacaine 3%
prilocaine 4%
What agents do you select when need for hemostasis?
Select agents with 1:50,000 or 1:100,000 epinephrine
- infiltrate locally into the surgical site
how many different drugs should you have in your office
Have a minimum of 2 different drugs of varying duration of action
What was the first synthetic local anesthetic?
Procaine (ester) = Novocain
- 1904
- used until lidocaine was developed in 1940s
Novocain is widely known for what characteristic?
Produces the greatest vasodilation of all currently used local anesthetics
How fast is the onset of action for novocain
slow onset of action (high pKa)
- no pulpal anesthesia
- only 15-30 minutes of soft tissue anesthesia
- half life of 6 minutes
how is novocain metabolized?
by plasma cholinesterase (like all esters)
What was added to procaine HCl to hasten its onset and to increase duration of action
Propoxycaine
T or F, Propoxycaine is often used alone but can be very toxic
False, never used alone, as it is very toxic = limited utility
What combination of esters was only combo in dental cartridge
Procaine HCl + propoxycaine
What was the first amide LA to be marketed?
Lidocaine HCl (1948) - replaced procaine as drug of choice for pain control
In comparison to procaine, lidocaine:
- Significantly more rapid onset of action (2-3 minutes)
- Produces more profound anesthesia
- Twice as potent as procaine
- Has longer duration of action
- Has greater potency
T or F, Allergy to amide LA isn’t common
True, it is virtually non-existent
- this is an advantage of lidocaine (and all amides)
Metabolites of lidocaine HCl
monoethylglyceine and xylidide
- **Pharmacologically active and potentially toxic
Where are lidocaine metabolites metabolized and excreted?
Metabolism = liver (1/3 drug undergoes hydrolysis) Excretion = kidneys (
T or F, Lidocaine is more vasodilating than prilocaine or mepivacaine
True
Onset of action for lidocaine HCl
Rapid onset (2-3 minutes)
Effective dental concentration for lidocaine HCl
2%
Does lidocaine HCl have a topical anesthetic action/
Yes; available in concentrations ranging from 2% to 10% in ointments
Lidocaine HCl pregnancy category
B
- safe during lactation; does not enter breast milk
3 formulations of lidocaine
- lidocaine 2% (no vasoconstrictor) light blue
- lidocaine 2% with epi 1:50,000 (green)
- lidocaine 2% with epi 1:100,000 (red)
What is the usefulness of lidocaine 2% plain?
very limited because of its vasodilating properties
- only 5-10 minutes of pulpal anesthesia
- higher blood levels
**Few applications for use of this drug in clinical practice
T or F, duration and depth of anesthesia is greater for lidocaine 2% with epi 1:50,000 than with epi 1:100,000
False, they duration and depth is equivalent
which version of lidocaine is concentration of choice?
- -> lidocaine 2% with epi 1:100,000 is preferred drug for most dental procedures (safer)
- especially for hyper-responders, elderly, ASA III or IV cardiac risk
- lidocaine 2% 1:50,000 is concentration of choice BUT poses risk in patient with heart disease.
Signs and symptoms of lidocaine toxicity
CNS stimulation followed by CNS depression
**First signs and symptoms of overdose may be drowsiness, leading to loss of consciousness and respiratory arrest
What specific properties does lidocaine possess outside of dental procedures?
Possess anticonvulsant properties
available versions of mepivacaine HCl?
- 3% mepivacaine HCl (no vasoconstrictor)
2. 2% mepivacaine HCl w/ levonordefrin 1:20,000
Mepivacaine is chemically similar to what other LA? Pharmacologically similar to what other LA?
Chemically: bupivacaine
Pharmacologically: lidocaine
- lacks duration of bupivacaine
Which LA is the weakest vasodilator of all injectable amide LA?
Mepivacaine HCl
- mild vasodilating properties = longer acting than other LA without vasoconstrictors
Indications for Mepivacaine?
- Short/minor procedures requiring neither lengthy or profound pulpal anesthesia
- Patients with contraindications to vasoconstrictor
Signs and symptoms of overdose of mepivacaine
Follow more classic presentation
- CNS stimulation followed by depression
- -> absence of CNS stimulation phase with immediate depression is rare
Potency of Mepivacaine HCl
- Twice as potent as procaine
- Equal to lidocaine and prilocaine
- 2/3 as potent as articaine
- 1/4 as potent as bupivacaine
Mepivacaine is similar in toxicity to what?
articaine
lidocaine
Metabolism and excretion of mepivacaine
Liver via hydroxylation and N-demethylation
Via kidneys = ~1-16% of dose excreted unchanged
Why is it good to know that mepivacaine is the weakest vasodilator of all 5 injectable LA drugs in dental form?
Because it allows it to be used without a vasoconstrictor
Onset of action for mepivacaine HCl
Rapid (1-2 minutes)
Mepivacaine HCl pregnancy category
C
- Not known whether crosses into breast milk; use caution
Pharmacologically, prilocaine is similar to what?
mepivacaine
What is the risk found with prilocaine?
can reduce the blood’s oxygen carrying capability, which may lead to a specific type of anemia
- methemoglobinemia
How does prilocaine differ from lidocaine and mepivacaine?
Chemical ring structure is different
Aromatic ring is linked to a secondary amine
- other amide LA are all linked to tertiary amines
Metabolites of prilocaine
Orthotoluidine
N-propylalanine
**Carbon Dioxide is major end-product of biotransformation
Which metabolic of prilocaine induces formation of methemoglobin
Orthotoluidine
T or F, Lidocaine is metabolized much more rapidly and completely than prilocaine
False, Prilocaine is metabolized much more rapidly and completely than lidocaine
Biotransformation of prilocaine takes place where?
Liver
- also in lungs and kidney**
Prilocaine is excreted via?
Kidneys
***Renal clearance is faster than for all other amides
How toxic is Prilocaine in comparison to comparable potent amides?
Less toxic systemically
- less toxic because it is removed from circulation faster
Prilocaine is available in 2 formulations:
Prilocaine 4% (plain)
Prilocaine 4% w/ epi 1:200,000
How useful is prilocaine 4% (plain)
Frequently able to provide anesthesia of equal duration seen with lidocaine or mepivacaine with vasoconstrictor
How much of a vasodilator is prilocaine?
Weak vasodilator
- can get good clinical effects without a vasoconstrictor (not as weak as mepivacaine)
Prilocaine 4% w/ epi 1:200,000 is good for what patients?
good for epinephrine-sensitive patients with the least concentrated dilution of epinephrine but still provides lengthy anesthesia
Contraindications to prilocaine
- idiopathic or congenital methemoglobinemia
- hemoglobinopathies (sickle cell anemia)
- anemia
- cardiac or respiratory failure with hypoxia
- acetaminophen or phenacetin
Potency of prilocaine
- twice as potent as procaine
- equal to lidocaine and mepivacaine
- 2/3 as potent as articaine
- 1/4 as potent as bupivacaine
toxicity of prilocaine
half as toxic as lidocaine
Describe the metabolism comparisons between prilocaine and lidocaine
Prilocaine is more rapid and complete biotransformation than lidocaine
Place the vasodilating properties in order for procaine, lidocaine, mepivacaine and prilocaine
- mepivacaine (weakest)
- Prilocaine
- lidocaine 3. Articaine
- procaine
topical anesthetic action for prilocaine
Only in combination with other drugs; 2.5% lidocaine + 2.5% prilocaine
Prilocaine pregnancy category
B
- thought to enter into breast milk; use with caution
Describe the ring structure for articaine
Amide
- Thiophene ring (lipophilic) for aromatic ring
- contains an ester side chain off ring structure
- Sulfur atom within ring structure = eases passage through neural membrane = increased lipid solubility
Where does biotransformation occur for articaine
Plasma (ester) and liver (amide)
What makes the biotransformation of articaine different than other amide components?
Because of the ester component, this allows for rapid biotransformation = majority of drug is metabolized in plasma (approx. 90%)
- short half life… only 20 minutes (lidocaine = 90 minutes)
Which LA has the most rapid onset of all five injectable amide LA?
Articaine
T or F, Artisane is not effective without a vasoconstrictor
True
Available formulations of articaine
articaine 4% with epinephrine 1:100,000
articaine 4% with epinephrine 1:200,000
T or F, artisane presents less risk for systemic toxicity? why
True, because of its rapid metabolism and clearance
T or F, multiple cases of methemoglobinemia have been reported with usual use of articaine in dentistry
False, NO cases
Potency of articaine
- twice as potent as procaine
- 1/3 more potent than lidocaine, mepivacaine and prilocaine
- 1/3 as potent as bupivacaine
metabolism for articaine
amide = liver ester = plasma (cholinesterase)
Excretion for articaine
Kidneys (less than 2% is excreted unchanged)
Pregnancy category or articaine
C
- may enter breast milk; use with caution
2 primary indications for bupivacaine
- Lengthy dental procedures requiring pulpal anesthesia for longer than 90 minutes
- Management of post-operative pain
- Need for post-op opioids is significantly reduced
Describe onset for bupivacaine
For some it is normal as in other amides (2-4 minutes)
- **But for many, onset is delayed to 6-10 minutes
Which amide LA has the slowest onset of all amide LA
bupivacaine
- due to high pKa
T or F, bupivacaine is recommended for adult patients as well as younger patients including children and toddlers
False, NOT recommended for children and for patients at risk for self-injury
Which amide LA is the most potent vasodilator of all injectable amide LA?
bupivacaine
- However it isn’t as potent as procaine (ester is most potent)
Why is bupivacaine capable of producing prolonged anesthesia
- due to strong receptor binding in sodium channels
- can last for up to 12 hours = LONGEST ACTING AMIDE LA
bupivacaine will not be metabolized or cleared as quickly in what patients?
with compromised cardiovascular system
Explain overdoses and their occurrence with bupivacaine
Overdoses are common
When overdose occurs, it is more severe and less easily reversed
- Cardiotoxic
available form of bupivacaine
bupivacaine 0.5% with epinephrine 1:200,000
describe metabolism & excretion of bupivacaine
M: Liver by amidases (slow)
E: Kidney
What is the most toxic LA
bupivacaine
Pregnancy category of bupivacaine
C
- may enter breast milk; use with caution
Use of topical anesthetic is important for what reason?
atraumatic injection technique
- pre-injection numbing
T or F, Concentration for the same drug applied topically is lower than what is used via injection
False, HIGHER
** Higher concentrations increase risk for toxicity
T or F, LA are vasodilators = topical agents also contain vasoconstrictors
False, they do not contain vasoconstrictors
- able to get absorbed
- some quickly
T or F, many injectable LA are ineffective as topical because the concentrations necessary to produce topical anesthesia are too high
True
- significantly increases risk for overdose and local tissue toxicity
Which LA are NOT used topically
Articaine Mepivacaine Prilocaine (only in combination topical anesthetics) Procaine Bupivacaine
Topical anesthesia is effective only where?
on surface tissues (2-3 mm)
Formulations for topical anesthestics
Ointments
gels
solutions
sprays
Benzocaine has what ring structure
ester
T or F, Benzocaine is not suitable for injection
True
Why is dyclonine hydrochloride chemically unique?
Ketone
- excellent for patients with known sensitivities to other LA
Potency of dyclonine hydrochloride is equal to that of what other LA
Cocaine
Onset of action for dyclonine hydrochloride
slow (up to 10 minutes) but lasts for up to 1 hour
Lidocaine is available in what 2 forms for topical application?
- lidocaine base
2. lidocaine hydrochloride
Most potent of dental topical anesthetics
tetracaine hydrochloride
Cetacaine contains what compounds?
benzocaine, butamben, and tetracaine
- contains 3 esters
2 formulations of 2.5% lidocaine with 2.5% prilocaine
- EMLA = primarily used in medicine
2. Oraqix = specifically formulated for dentistry
Characteristics of eutectic mixtures
- Provide more rapid onset on skin
- greater depth of topical penetration on both skin and mucous membranes
- higher concentrations of base forms of drugs
What eutectic mixture is used for intrapockets?
Oraqix
- applied into gingival pocket
