1. Local Anaesthetic Agents In Clinical Use
Dr. Omar Karadsheh
1/11/2015

2. Outline Background Selection Of A Local Anaesthetic agent
Maximum doses of local anaesthetic agents
Most common local anaesthetic agents used in dentistry
Topical Anaesthetic agents

3. Background
In 1980, five local anaesthetics were available in dental cartridge form in the United States: lidocaine, mepivacaine, prilocaine, and the combination of procaine and propoxycaine.
Long acting agents bupivacaine (1982 Canada, 1983 United States) and etidocaine (1985).
In 1975, articaine became available in Germany, and later throughout Europe. Articaine came to North America in 1983 (Canada) and to the United States in 2000.
The combination of procaine and propoxycaine was withdrawn from the U.S. market in January 1996
rationale for selection of an appropriate local aenesthetic for a given patient at a given appointment taking into account relative and absolute C/I

4. Selection of Local Anaesthetic agents
The duration of pulpal (hard tissue) and soft tissue (total) anaesthesia needed
Need for Postoperative pain management
Need for Haemostasis
Absolute and relative C/I

5. Approximate Duration of Action of Local Anaesthetics
Short Duration (Pulpal Anesthesia Approximately 30 Minutes)
Mepivacaine HCl 3%
Prilocaine HCl 4% (by infiltration)
Intermediate Duration (Pulpal Anesthesia Approximately 60 Minutes)
Articaine HCl 4% + epinephrine 1:100,000
Articaine HCl 4% + epinephrine 1:200,000
Lidocaine HCl 2% + epinephrine 1:50,000
Lidocaine HCl 2% + epinephrine 1:100,000
Mepivacaine HCl 2% + levonordefrin 1:20,000
Prilocaine HCl 4% (via nerve block only)
Prilocaine HCl 4% + epinephrine 1:200,000
Long Duration (Pulpal Anesthesia Approximately 90+ Minutes)
Bupivacaine HCl 0.5% + epinephrine 1:200,000 (by nerve block)

6. Duration and Depth of Anaesthesia
Individual response to the drug (the “bell-shaped” curve)
Accuracy in deposition of the local anaesthetic
Status of tissues at the site of drug deposition (vascularity, pH)
Anatomic variation
Type of injection administered (supraperiosteal [“infiltration”] or nerve block)

7. Normal distribution curve (bell-shaped curve):
Variation in individual response to a drug is common and expected and is depicted in the so-called bell or normal distribution.

8. Normal distribution curve (bell-shaped curve):
Most patients will respond in a predictable manner to a drug's actions (e.g., 40 to 60 minutes). However, some patients (with none of the other factors that influence drug action obviously present) will have a shorter or longer duration of anesthesia. This is to be expected and is entirely normal.

9. Accuracy in administration
Although not as significant in certain techniques (e.g., supraperiosteal) or with certain drugs (e.g., articaine),
Accuracy in deposition is a major factor in many nerve blocks in which a considerable thickness of soft tissue must be penetrated to access the nerve being blocked.
Deposition of local anaesthetic close to the nerve provides greater depth and duration of anaesthesia compared with an anaesthetic deposited at a greater distance from the nerve to be blocked.

10. The status of the tissues into which a local anesthetic is deposited
Inflammation, infection, or pain (acute or chronic) usually decreases depth and anticipated duration of anaesthesia.
Increased vascularity more rapid absorptiondecreased duration of anesthesia.
Buffered local anaesthetics
The Gow-Gates mandibular nerve block Vs IANB

11. Anatomic variation Mandible Maxilla height of the mandibular foramen,
width of the ramus,
thickness of the cortical plate of bone
Maxilla
the zygomatic arch
Palatal roots

12. Type of Injection Administered
Blocks Vs. Infiltration
Less than recommended volumes decrease the duration of action. Larger than recommended doses do not provide increased duration.
For example,
infiltration injection with plain prilocaine 4% 10-15 min pulpal anaesthesia
nerve block with plain Prilociaine 4% 40- to 60-minute pulpal anaesthesia

14. Maximum doses of L.A Unlikely to be reached.
Milligrams per kilogram (mg/kg) or as milligrams per pound (mg/lb).
Only estimated values (Bell-shaped curve):
Normal responders Hypo-responders Hyper-responders
Always minimize drug doses and use the smallest clinically effective dose
For patients whose responses to anesthetic blood levels lie within the middle of the normal distribution curve, administration of a maximum dose based on body weight produces a local anesthetic blood level below the usual threshold for an overdose (toxic) reaction. The response observed if an overdose reaction occurs at that dose is mild (e.g., tremor of the arms and legs, drowsiness). Patients who are hypo-responders to elevated local anesthetic blood levels may not experience any adverse reaction until their local anesthetic blood level m
is considerably above this “normal” overdose threshold. These patients represent little increased risk when local anesthetics are administered in “usual” dental doses. However, hyperresponders may demonstrate clinical signs and symptoms of local anesthetic overdose at blood levels that are considerably lower than those normally necessary to produce such reactions. To increase safety for all patients during administration of local anesthetics, but especially in this latter group, one should always minimize drug doses and use the smallest clinically effective dose

15. Maximum doses of L.A agents
Two groups of patients represent potentially increased risk from overly high local anaesthetic blood levels:
the smaller, lighter-weight (and well-behaved) child,
the debilitated elderly individual.
Medically compromised (Blood, liver and kidney problems)
The calculated drug dose (based on body weight) should be decreased in all “at risk” individuals.
It is suggested that the doctor evaluate each patient's dental care needs and then devise a treatment plan that takes into account that person's requirement for smaller doses of local anaesthetic at every treatment appointment.
Maximum doses are unlikely to be reached in most dental patients, especially adults of normal body weight, for most dental procedures.
The maximum recommended dose calculated should always be decreased in medically compromised, debilitated, or elderly persons. Changes in liver function, plasma protein binding, blood volume, and other important physiologic functions influence the manner in which local anesthetics are distributed and biotransformed in the body
The half-lives of the amide local anesthetics are significantly increased in the presence of decreased liver function or perfusion.
Unfortunately, there is no magical formula that can aid in determining the degree of dose reduction for a given patient.

16. Overdose (OD)
When the MRD is exceeded, there is no guarantee that an OD will occur, only that there is a greater likelihood of its occurrence.
An OD may be seen with dosages below the calculated MRD (hyper- responders to the drug).
Another factor in determining whether an OD will occur is the time over which the local anaesthetic dose was administered.

19. Calculation of Maximum dosage and Number of Cartridges (single drug)
Patient: 22 years old, Healthy, Female, 50 kg L.A: Lidocaine HCL + Epinephrine 1:100,000 MRD Lidocaine: 7 mg/kg Lidocaine 2%  x 10 = 20 mg/ml Cartridge contains 1.8 ml solution ,so  20 x 1.8 = 36mg/cartridge Maximum dose for this patient is: 7 mg/kg x 50 = 350 mg Number of cartridges= 350/36 = ~10

23. Local Anaesthetic Agents Used in Dental Injections
Ester Type
Procaine
Propoxycaine HCl
Mixture of Procaine + Propoxycaine
Amide Type
Mepivacaine
Prilocaine
Lidocaine
Articaine
Bupivacaine

24. Procaine HCL

25. Procaine HCL
Until 1996, procaine was found in dental cartridges in combination with a second ester anesthetic, propoxycaine.
2% procaine (plain) provides essentially no pulpal anaesthesia and from 15 to 30 minutes of soft tissue anaesthesia.
Procaine produces the greatest vasodilation of all clinically used local anaesthetics.
Procaine is of importance in the immediate management of inadvertent intra-arterial (IA) injection of a drug; its vasodilating properties are used to aid in breaking arteriospasm.
Although not extremely common, Allergy to esters > amides
Procaine does not exhibit increased toxicity in patients with hepatic dysfunction.
Procaine has a slow clinical onset of anesthesia (6 to 10 minutes) (pKa of 9.1 )—a reason for inclusion of propoxycaine in the anesthetic cartridge.
Used as the sole local anesthetic agent for pain control in dentistry, as it was from its introduction in 1904 until the introduction of the amide local anesthetic lidocaine in the mid-1940s

26. Propoxycaine

27. Mixture
Propoxycaine was combined with procaine in solution to provide more rapid onset and a more profound and longer-lasting anesthesia than could be obtained with procaine alone
. Propoxycaine was not available alone because its higher toxicity (seven to eight times that of procaine) limited its usefulness as a sole agent.
0.4% propoxycaine/2% procaine with 1:20,000 levonordefrin (United States) or with 1:30,000 norepinephrine (Canada) provided approximately 40 minutes of pulpal anesthesia and 2 to 3 hours of soft tissue anaesthesia.
The use of norepinephrine in local anesthetic solutions is no longer recommended, especially in areas where prolonged ischemia can lead to tissue necrosis. In the oral cavity, this is most likely to be seen in the palate.

28. Amide-Type Local Anesthetics

29. Lidocaine HCL

30. Lidocaine HCL

31. Compared with procaine, lidocaine possesses :
Lidocaine had replaced procaine (Novocaine) as the most widely used local anaesthetic in both medicine and dentistry.
Compared with procaine, lidocaine possesses :
a significantly more rapid onset of action (3 to 5 minutes vs. 6 to 10 minutes),
produces more profound anaesthesia,
has a longer duration of action,
and has greater potency.
Allergy to amide local anaesthetics is virtually non-existent; true, documented, and reproducible allergic reactions are extremely rare,

32. Lidocaine Preparations
2% lidocaine without epinephrine (2% “plain”) is no longer available in dental cartridges in North America. Two Percent Lidocaine HCl Without a Vasoconstrictor (Lidocaine Plain) Its vasodilating properties severely limit the duration and the depth of pulpal anesthesia (5 to 10 minutes).
This vasodilatory effect leads to (1) higher blood levels of lidocaine, with an attendant increase in the risk of adverse reactions, along with (2) increased perfusion in the area of drug deposition. Few clinical indications are known for the use of 2% lidocaine without a vasoconstrictor in the typical dental practice. As of August 2011, 2% lidocaine without epinephrine (2% “plain”) was no longer available in dental cartridges in North America.

34. Lidocaine 2% + Epinephrine
Decreased bleeding caused by the α-stimulating actions of epinephrine.
The local anaesthetic is absorbed into the cardiovascular system more slowly leading to an increase in both depth and duration of anaesthesia:
approximately 60 minutes of pulpal anaesthesia and 3 to 5 hours of soft tissue anaesthesia.
2) (thereby remaining at the site of administration longer, it is hoped near the nerve),

35. Two Percent Lidocaine With Epinephrine 1:50,000
1:50,000 epinephrine concentration is equal to 20 µg/mL,
Cartridge has 1.8 ml  36 µg per cartridge.
For patients weighing more than 45 kg (100 lb),the maximum epinephrine dose of 200 µg for the healthy patient.
The MRD for epinephrine-sensitive individuals (e.g., certain cardiovascularly compromised {ASA} 3], and clinically hyperthyroid patients [ASA 3]) is 40 µg per appointment. This is equivalent to about one cartridge of 1:50,000 epinephrine
The only recommended use of 2% lidocaine with a 1:50,000 epinephrine concentration is for haemostasis (a situation wherein only small volumes are infiltrated directly into the surgical site).
patients [American Society of Anesthesiologists Physical Status classification system

36. Two Percent Lidocaine With Epinephrine 1:100,000
Administration of 2% lidocaine with epinephrine 1:100,000 decreases blood flow into the area of injection  less bleeding and longer duration of action
The epinephrine dilution is 10 µg/mL, or 18 µg per cartridge.
Epinephrine-sensitive patients should be limited to two cartridges of 1:100,000 epinephrine per appointment.

37. Which Lidocaine preparation?
In terms of duration and depth of anaesthesia for most procedures in a typical dental patient, 2% lidocaine with 1:100,000 epinephrine is preferred to 2% lidocaine with 1:50,000 epinephrine
2% lidocaine with 1:200,000 or 1:300,000 epinephrine provides the same duration of pulpal and soft tissue anaesthesia, although not the same level of haemostasis, their use is recommended in elderly patients or hyper- responders to epinephrine

38. Concluding Notes
The 1:50,000 solution provides excellent haemostatic action. The 1:100,000 dilution also may be used for hemostasis, but it is not as effective.
Rebound vasodilation occurs with both 1:50,000 and 1:100,000 epinephrine concentrations as the tissue concentration of epinephrine decreases.
Minimum volumes of solution should be administered to provide excellent haemostasis.
Signs and symptoms of lidocaine toxicity (overdose) may be the same (central nervous system [CNS] stimulation followed by CNS depression) as other agents.
However, the stimulatory phase may be brief or may not develop at all. Although muscle tremor and seizures commonly occur with overly high lidocaine blood levels, the first signs and symptoms of lidocaine overdose may include drowsiness, leading to loss of consciousness and respiratory arrest.

39. Mepivacaine HCl

40. Mepivacaine HCl

42. Three Percent Mepivacaine Without a Vasoconstrictor
For patients in whom a vasoconstrictor is not indicated
For dental procedures requiring neither lengthy nor profound pulpal anaesthesia.
Mepivacaine plain is the most used local anaesthetic in paediatric patients when the treating doctor is not a paediatric dentist (e.g., is a general practitioner) and often is quite appropriate in the management of geriatric patients.

44. Two Percent Mepivacaine With a Vasoconstrictor, Levonordefrin 1:20,000
Depth and duration of anaesthesia is similar to Lidocaine combinations.
Mepivacaine is available in combination with levonordefrin (1:20,000). Where hemostasis is desired, epinephrine is preferred to levonordefrin
Signs and symptoms of mepivacaine overdose usually follow the more typical pattern of CNS stimulation followed by depression.
Although possible, absence of stimulation with immediate CNS depression (e.g., drowsiness and unconsciousness, as is seen more commonly with lidocaine) is rare with mepivacaine

45. Prilocain HCL Potency:2 (procaine = 1; lidocaine = 2).
Toxicity: 1 (procaine = 1; lidocaine = 2); 40% less toxic than lidocaine.
Vasodilating Properties: Prilocaine is a vasodilator. It produces greater vasodilation than is produced by mepivacaine but less than lidocaine
pKa 7.9.
Onset of Action : Slightly slower than that of lidocaine (3 to 5 minutes).
Effective Dental Concentration 4%.
Anaesthetic Half-Life: 1.6 hours.
Topical Anaesthetic Action:
Not in clinically acceptable concentrations.
Prilocaine, in its uncharged base form, is an integral part of EMLA cream

46. Prilocaine HCL Metabolism:
Is significantly different from lidocaine and mepivacaine,it undergoes more rapid and complete biotransformation
Orthotoluidine, a by-product, can induce the formation of methemoglobin, producing methemoglobinemia if large doses are administered reducing the blood's oxygen-carrying capacity, at times sufficiently to cause observable cyanosis.
Limiting the total prilocaine dose to 600 mg (FDA recommendation) avoids symptomatic cyanosis.
Excretion:
Prilocaine and its metabolites are excreted primarily via the kidneys. Renal clearance of prilocaine is faster than for other amides, resulting in its faster removal from the circulation.
Pregnancy Classification B Safety During Lactation : Unknown.

47. Prilocaine Preparations

48. Infiltration with Prilocaine 4% plain provides short durations of pulpal (10 to 15 minutes) and soft tissue ( to 2 hours) anesthesia,
whereas regional nerve block provides pulpal anesthesia for up to 60 minutes (commonly 40 to 60 minutes) and soft tissue anesthesia for 2 to 4 hours. Thus prilocaine plain frequently is able to provide anaesthesia that is equal in duration to that attained with lidocaine or mepivacaine with a vasoconstrictor.
Prilocaine with epinephrine provides lengthy anaesthesia while offering a less concentrated epinephrine dilution: 1:200,000.
In epinephrine-sensitive patients requiring prolonged pulpal anesthesia (≥60 minutes), prilocaine plain or with 1:200,000 epinephrine is strongly recommended. It is rapidly biotransformed and, for this reason, is considered to be a safe local anaesthetic (e.g., lower toxicity)

49. C/I of Prilocaine
Prilocaine is relatively contraindicated in patients with idiopathic or congenital methemoglobinemia, hemoglobinopathies (sickle cell anemia), anemia, or cardiac or respiratory failure evidenced by hypoxia, because methemoglobin levels are increased, decreasing oxygen-carrying capacity.
Prilocaine administration is also relatively contraindicated in patients receiving acetaminophen or phenacetin, both of which produce elevations in methemoglobin levels.
Neurotoxicity and paresthesia ?

50. Articaine HCl
Classification : Hybrid molecule. Classified as an amide; however, it possesses both amide and ester characteristics.
Potency 1.5 times that of lidocaine; 1.9 times that of procaine.
Toxicity Similar to lidocaine and procaine.

51. Articaine HCL
Metabolism : Articaine is the only amide-type local anesthetic that contains a thiophene group. Because articaine HCl is the only widely used amide-type local anesthetic that contains an ester group, biotransformation of articaine HCl occurs in both plasma (hydrolysis by plasma esterase) and liver (hepatic microsomal enzymes).
Excretion: Via the kidneys; approximately 5% to 10% unchanged, approximately 90% metabolites.
Vasodilating Properties: Articaine has a vasodilating effect equal to that of lidocaine. Procaine is slightly more vasoactive.

52. Anaesthetic Half-Life: 0.5 hours [27 minutes].
Onset of Action:
Articaine 1:200,000, infiltration 1 to 2 minutes, mandibular block 2 to 3 minutes;
Articaine 1:100,000, infiltration 1 to 2 minutes, mandibular block 2 to 3 minutes.
Effective Dental Concentration: 4% with 1:100,000 or 1:200,000 epinephrine.
Anaesthetic Half-Life: 0.5 hours [27 minutes].
Topical Anaesthetic Action: Not in clinically acceptable concentrations.
Pregnancy Classification: C.
Safety During Lactation: Unknown (use with caution in females who are breast- feeding because it is not known whether articaine is excreted in milk).
Maximum Recommended Dose: The FDA maximum recommended dose is 7.0 mg/kg or 3.2 mg/lb of body weight for the adult patient

54. Articaine HCL Articaine, as the newest local anaesthetic drug marketed
It has been claimed that articaine is able to diffuse through soft and hard tissues more reliably than other local anesthetics
Clinically, it is claimed that following maxillary buccal infiltration, articaine on occasion may provide palatal soft tissue anesthesia, obviating the need for palatal injection
The significant success of articaine administered by buccal infiltration in the mandible of adult patients.
Reports of paraesthesia following local anaesthetic administration. An overwhelming majority of reported cases occurred following inferior alveolar nerve block and primarily involved the lingual nerve

55. Articaine HCL relative C/I
Articaine HCl should be used with caution in persons with hepatic disease and significant impairment in cardiovascular function
Class C drug during pregnancy.
Use with caution in females who are breast-feeding
Administration to children younger than 4 years is not recommended because insufficient data are available to support such usage.

56. Bupivacaine HCl

57. Bupivacaine HCL

58. Bupivacaine HCL MRD bupivacaine is 90 mg.
Bupivacaine is available as a 0.5% solution with 1:200,000 epinephrine
Two primary indications for its utilization in dentistry:
Lengthy dental procedures for which pulpal (deep) anesthesia in excess of 90 minutes is necessary (e.g., full mouth reconstruction, implant surgery, extensive periodontal procedures)
Management of postoperative pain (e.g., endodontic, periodontal, postimplant, surgical) The patient's requirement for postoperative opioid analgesics is considerably lessened.

59. Relative C/I
Bupivacaine is not recommended in younger patients or in those for whom the risk of postoperative soft tissue injury produced by self-mutilation is increased, such as physically and mentally disabled persons.
Bupivacaine is rarely indicated in children because pediatric dental procedures are usually of short duration.

61. Anesthetics For Topical Application
Conventional topical anesthetics are unable to penetrate intact skin but do diffuse through abraded skin (e.g., sunburn) and any mucous membranes.
The concentration of a local anaesthetic applied topically is typically greater than that of the same local anaesthetic administered by injection.
The higher concentration facilitates diffusion of the drug through the mucous membrane. Higher concentration also increases the risk of toxicity, both locally to tissues and systemically if the drug is efficiently absorbed.
Do not contain vasoconstrictors and local anesthetics have vasodilatory properties.

62. Many local anesthetics used effectively via injection prove ineffective when applied topically (e.g., articaine HCl, mepivacaine HCl, prilocaine HCl, procaine HCl) because the concentrations necessary to produce anesthesia via topical application are high, with significantly increased overdose and local tissue toxicity potential .
As a general rule, topical anesthetics are effective only on surface tissues (2 to 3 mm). Tissues deep to the area of application are poorly anesthetized, if at all. However, surface anesthesia does allow for atraumatic needle penetration of the mucous membrane

63. The topical anesthetics benzocaine and lidocaine base (not the HCl form used by injection) are insoluble in water. However, they are soluble in alcohol, propylene glycol, polyethylene glycol, and other vehicles suitable for surface application. The base forms of benzocaine and lidocaine are slowly absorbed into the cardiovascular system and therefore are less likely to produce an overdose reaction following typical dental application.
Some topical anesthetics are marketed in pressurized spray containers. Although they are no more effective than other forms, it is difficult to control the amount of anaesthetic expelled and to confine it to the desired site of application. Spray devices that do not deliver measured doses should not be used intraorally.

64. Topical Anaesthesia

65. Benzocaine Benzocaine (ethyl p-aminobenzoate) is an ester
Poor solubility in water
Poor absorption into the cardiovascular system
Systemic toxic (overdose) reactions virtually unknown
Remains at the site of application longer, providing a prolonged duration of action
Not suitable for injection
Inhibits the antibacterial action of sulfonamides
Availability (Benzocaine is available in the following formulations in numerous dosages: aerosol, gel, gel patch, ointment, and solution.)

66. Topical Agents
Cocaine hydrochloride is an ester that occurs naturally as a white crystalline solid that is highly soluble in water:
Used exclusively via topical application.
Injection of cocaine is contraindicated because its highly toxic
Onset of topical anesthetic action is quite rapid, usually occurring within 1 minute.
Duration of anesthetic action may be as long as 2 hours.
It is absorbed rapidly but eliminated slowly (elimination half-life = 42 minutes). .

67. Cocaine
Cocaine is the only local anaesthetic consistently demonstrated to produce vasoconstriction
Potentiate the actions of endogenous epinephrine and norepinephrine.
Addition of vasoconstrictors to cocaine therefore is unnecessary and is potentially dangerous, increasing the likelihood of dysrhythmias, including ventricular fibrillation

68. Classified as a Schedule II drug under the Controlled Substances Act
Classified as a Schedule II drug under the Controlled Substances Act. Repeated use results in psychological dependence and tolerance.
Overdose of cocaine is not uncommon following illicit use, primarily because the drug is readily absorbed from the nasal mucosa and its dosage is not carefully monitored.
Clinical manifestations of mild overdose include euphoria, excitement, restlessness, tremor, hypertension, tachycardia, and tachypnea.
Clinical manifestations of acute cocaine overdose include excitement, restlessness, confusion, tremor, hypertension, tachycardia, tachypnea, nausea and vomiting, abdominal pain, exophthalmos, and mydriasis; these are followed by depression (CNS, cardiovascular, respiratory) and death from respiratory arrest.

69. It is recommended that the concentration of cocaine not exceed 4% for topical application to oral mucous membranes.
Solutions of cocaine are unstable and deteriorate on standing.
Because of the extreme abuse potential of cocaine, its use as a topical anesthetic in dentistry is not recommended.
Topically applied cocaine is used occasionally before nasal-endotracheal intubation is performed in the operating theater to minimize bleeding from this highly vascular region and pain as the endotracheal tube is passed.

70. Dyclonine Hydrochloride
Dyclonine hydrochloride) is a ketone derivative without an ester or amide linkage that may be used in patients who are allergic to the common anesthetics.
Dyclonine offers advantages over other topical anesthetic agents
it to be effective and safe.
Cross-sensitization with other local anesthetics does not occur
Slightly soluble in water
Potency equal to that of cocaine
Onset of anesthesia slow, requiring up to 10 minutes
Duration of anesthesia may be as long as 1 hour.
Systemic toxicity is extremely low, primarily because of the agent's poor water solubility.
Not indicated for use by injection; irritating to tissues at the site of application 8 A 0.5% solution is used in dentistry. Maximum recommended dose is 200 mg (40 mL of a 0.5% solution). 9 Dyclonine was available as Dyclone in a 0.5% solution: each 100 mL of solution contained 500 mg of dyclonine HCl, 300 mg of chlorobutanol as a preservative, sodium chloride for isotonicity, and hydrochloric acid, as needed, to adjust pH. The Dyclone brand was withdrawn from the North American market in 2001.

71. EMLA (Eutectic Mixture of Local Anesthetics)
EMLA cream (composed of lidocaine 2.5% and prilocaine 2.5%) is an emulsion in which the oil phase is a eutectic mixture of lidocaine and prilocaine in a ratio of 1:1 by weight.
provide surface anesthesia for intact skin (other topical anesthetics do not produce anesthesia on intact skin, only abraded skin
Used primarily before painful procedures such as venipuncture and other needle insertions
EMLA has gained popularity among needle-phobic adults and persons having other superficial, but painful, procedures performed (e.g., hair removal
Because intact skin is a barrier to drug diffusion, EMLA must be applied 1 hour before the procedure. Satisfactory numbing of the skin occurs 1 hour after application, reaches a maximum at 2 to 3 hours, and lasts for 1 to 2 hours after removal.
EMLA is supplied in a 5-g or 30-g tube or as an EMLA anesthetic disc

72. EMLA
EMLA is contraindicated for use in patients with congenital or idiopathic methemoglobinemia, infants younger than 12 months who are receiving treatment with methemoglobin-inducing agents, and patients with known sensitivity to amide-type local anesthetics or any other component of the product.
“EMLA is not recommended for use on mucous membranes,” subsequent clinical trials have demonstrated satisfactory results.
Bernardi and associates demonstrated statistically significant analgesia in 52 dental patients requiring removal of metal maxillary or mandibular splints used to contain fractures. A study showed that use of EMLA could eliminate to some extent use of the needle in procedures performed in pediatric dentistry.

73. Lidocaine Lidocaine is available in two forms for topical application:
lidocaine base, which is poorly soluble in water, is used as a 5% concentration, and is indicated for use on ulcerated, abraded, or lacerated tissue;
and lidocaine hydrochloride, its water-soluble preparation, which is used as a 2% concentration. The water- soluble form of lidocaine penetrates tissue more efficiently than the base form. However, systemic absorption is also greater, providing greater risk of toxicity than the base form.
Maximum recommended dose following topical application is 200 mg.
Availability: Lidocaine base is available as an aerosol spray, ointment, patch, and solution in various dosage forms
Lidocaine HCl is available as an oral topical solution in 20 mg/mL (viscous) and 40 mg/mL (solution).

75. Tetracaine Hydrochloride
Tetracaine hydrochloride) is a long-duration ester local anaesthetic that can be injected or applied topically, Highly soluble in water , Applied topically,
five to eight times more potent than cocaine
Onset of action after topical application is slow.
Duration of action is approximately 45 minutes after topical application.
Metabolized in plasma and the liver by plasma pseudocholinesterase at a slower rate than procaine
Rapidly absorbed through mucous membranes. Use should be limited to small areas to avoid rapid absorption. Other, more slowly or poorly absorbed agents should be used in lieu of tetracaine when larger areas of topical anesthesia are necessary
Maximum recommended dose of 20 mg when used for topical application. This represents 1 mL of a 2% solution.
Caution is urged because of great potential for systemic toxicity.

76. Availability (Canada): a Aerosol: 0.7 mg/metered spray 1 Supracaine
Tetracaine in a 3% concentration, with the vasoconstrictor oxymetazocine, has been shown to provide pulpal anesthesia of maxillary teeth when administered by aerosol spray into a patient's nares.

77. Summary

79. Summary Amides are preferred to esters whenever possible:
A minimum of two drugs is recommended for most offices:
1 Short-duration pulpal anaesthetic (≈30 minutes)
2 Intermediate-duration pulpal anaesthetic (≈60 minutes)
3 Long-duration pulpal anaesthetic (90 or more minutes)
4 Topical anaesthetic for tissue preparation before injection of local anaesthetic

81. Thank You