clinical action of specific agents

8/13/2019 Clinical Action of Specific Agents

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CLINICAL ACTIONOF SPECIFIC

AGENTS



INTRODUCTION

With the availability of various localanesthetics with or withoutvasoconstrictors, it is now possible for a

doctor to select a drug possessing specificpain controlling properties necessary forthe patient for a given dental procedure.

Before discussing the clinical actions of

various local anesthetics it is necessary tounderstand the concepts like

1) Duration of action

2) Determination of maximum recommended

dose.



DURATION

Factors affecting the depth and duration of

action are:

1) Individual response to the drug (“Bell shaped curve”)



DURATION

2. Accuracy in deposition of LA

3. Status of the tissues at the site ofdeposition ( Vascularity, pH)

4. Anatomical variation

5. Type of injection administered(supraperiosteal / infiltration) or nerveblock

Variation or individual response to a drugis common and is deposited in the socalled bell or normal distribution curve.



DURATION

Some individuals respond normal midregion

to duration of particular LA called as normal

responders.

Some will have anesthetic effect beyond the

normal duration of LA (i.e. pulpal & soft

tissue) – hypo responders.

In hypo responders the response is short ofthe normal duration of actions of a particular

drug.



DURATION

Accuracy of administration of LA isanother factor influencing drug action.Deposition of LA close to the nerveprovides greater depth and duration ofanesthesia.

Status of tissues: Healthy tissue

evokes normal effect of inflamed orinfected tissue decreases the depthand duration increased vascularityresults in decreased duration of

action.



DURATION

Other variables like size ,shape and

thickness of bone influences the depth

and duration of anesthesia. Type of injection administered, the

administration of nerve block provides

a longer duration of both pulpal and

soft tissue anesthesia.



MAXIMUM DOSE OF

LOCAL ANESTHETICS

It is presented in terms of milligrams per kgbody weight or milligrams per pound bodyweight.

The council on dental therapeutics of the American dental association and unitedstates pharmacopeial convention reviewedindependently and are of the view that the

maximum recommended dose should notbe adjusted for inclusion of avasoconstrictor.



MAXIMUM DOSE OF

LOCAL ANESTHETICS

For example the maximum dose of

lidocaine without a vasoconstrictor or

with a vasoconstrictor should be300mgs.

The maximum calculated drug dose

always should be decreased in

medically deblitated or elderly

patients.



MAXIMUM DOSE OF

LOCAL ANESTHETICS

When one or more local anesthetics

are used for a general treatment,

ensure that the total dose of both thelocal anesthetics not to exceed the

lower than the maximum doe of the

individual agents.



ESTER TYPE LOCAL

ANESTHETICS

Procaine HCl: prepared in 1904 to 1905;potency – 1; toxicity – 1; produces thegreatest vasodilatation of all LA’s.

Onset of action – 6 – 10 hrs

Dental concentration – 2% & 4%

Half life = 0.1 hr (6 mts) – no pulpalanesthesia 15- 30 minutes of soft tissueanesthesia.

First synthetic injectable local anesthetic – no longer available.

It is of importance in the immediatemanagement of inadvertent intra arterialinjection of drug – to break arteriospasm.

Maximum recommended dose is 1000 mg.



ESTER TYPE LOCAL

ANESTHETICS

Propoxycaine HCl: ester, potency 7-

8; toxicity 7-8.

It is combined with procaine to providemore rapid onset of rapid action.

Its usefulness is limited because of its

high toxicity – effective concentration0.4%.



ESTER TYPE LOCAL

ANESTHETICS

Procaine HCl + propoxycaine HCl: It wasuseful when amide were absolutelycontraindicated until 1996, the combinationwas only ester local anesthetic available indental cartridge form.

It is now as 0.4 % propoxyacine / 2%procaine with 1: 20,000 levonordefrin orwith 1:30,000 norepinephrine.

Provides 40 minutes of pulpal anesthesiaand 2-3 hrs of soft tissue anesthesia.Maximum recommended dose was 3mg/lbor 6.6 mg/kg body weight. For children3mg/lb.



AMIDE TYPE LOCAL

ANESTHETICS

Lidocaine HCl: prepared in 1943, approved

in 1948 Nov. Potency – 2; Toxicity – 2.

Vasodilating properties – less than procaine

more than prilocaine or mepivacaine. Pka 7.9 ; pH of plain solution 6.5; with

vasoconstrictor 5 to 5.5; Onset of action 3-5

minutes; dental concentration – 2 %; half

life – 1.6 hrs; maximum recommended dose – 300 mgs with or without adrenaline.

Lignocaine HCl was synthesized in 1943

and in 1948 became the first amide LA to

be marketed.



AMIDE TYPE LOCAL

ANESTHETICS

Within a few years of its introduction lidocaine replacedprocaine as the most widely used local anesthetic inboth medicine and dentistry a position it maintainstoday.

It represents the “ Gold Standard “ the drug to whichall new local anesthetics are compared.

2% lidocaine HCl without vasoconstrictor limits pulpalanesthesia to about 5 – 10 minutes.

2% lidocaine with epinephrine 1:50,000 produces a

decrease in blood flow because of its stimulatingaction of epinephrine. Leads to decreased duration ofaction approximately 60 minutes of pulpal anesthesiaand 3 – 5 hrs of soft tissue anesthesia.



AMIDE TYPE LOCAL

ANESTHETICS

The only recommended use of 2 % lidocaine with a1:50,000 epinephtrine for hemostasis ( where onlysmall volumes are infiltrated directly into the surgicalsite)

2% lidocaine HCl with 1: 100,000 epinephrine ispreferred to 1: 50,000 epinephrine.

In patients with ASA III and IV risks and in elderlypatients a greater dilution of 1: 100,000 or 1: 200,000should be used.

The first signs and symptoms of lidocaine overdosemay be overdose or drowsiness leading to loss ofconsciousness and respiratory arrest.



AMIDE TYPE LOCAL

ANESTHETICS

Half life – 1.9 hours.

Maximum recommended dose 3mg/lb

or 6.6 mg/kg. Maximum – 400 mgs. 3% Mepivaxcaine without a

vasoconstrictor is recommended forpatients in whom vasoconstrictor is

not indicated and for minor dentalprocedures requiring neither lengthynor profound anesthesia.



AMIDE TYPE LOCAL

ANESTHETICS

Mepivacaine plain is the most used

local anesthetic in paediatric patient.

Two vasoconstrictors levonordefrin1:20,000 and epinpehrine 1: 100,000

are available with mepivacaine

levonordefrin does nor provide the

intesnsity of hemostasis as

epinephrine.



AMIDE TYPE LOCAL

ANESTHETICS

Prilocaine HCl: Amide. Prepared in 1953and approved in 1965. Potency – 2; toxicity – 1 – 40% less toxic than plain liodcaine.

Being a secondary amine it is hyodrolysedstraight forwardly by hepatic amidase intoortho- toluidine and propylamine.

Ortho toluidine can producemethemoglobinemia if large doses are

administered. Methemoglobinemia can be revresed within

15 minutes administration of 1-2 mg/kgbody weight of 1% methylene blue solutionintravenously over a 5 minute period.



AMIDE TYPE LOCAL

ANESTHETICS

Pka 7.9. pH plain solution 4.5 withvasoconstrictor 3 – 4.0.

Onset of action is slower than lidocaine.

Effective dental concentration is 4%.

Half life 1.6 hrs.

Maximum recommended dose is 400mgs.

Prilocaine plain is able to provideanesthesia equal in duration to thatobtained from lidocaine or mepivacaine witha vasoconstrictor.



AMIDE TYPE LOCAL

ANESTHETICS

Prilocaine with epinephrine as low as 1:200,000dilution provides lengthy anesthetic containing 9 ug ofepinephrine in one dental cartridge 1.8 ml. It can besafely given to a ASA III patient upto 4 cartridges

(36ug). In epinephrine sensitive individuals requiring prolonged

pulpal anesthesia prilocaine plain or prilocaine with1:200,000 epinephrine is strongly recommended.

It is relatively contraindicated in patients with idiopathic

or congenital methemoglobinemia,hemoglobinopathies , anemia, cardiac or respiratoryfailure.

Also relatively contraindicated in patients receivingacetaminophen or phenactin.



AMIDE TYPE LOCAL

ANESTHETICS

Articaine HCl: prepared in 1969. FDA

approved in april 2000.

Potency – 1.5 times that of lidocaine and

1.9 times that of procaine.

Toxicity: Similar to lidocaine & prilocaine.

It is the only local anesthetic that contains

thiophene group and also the only usedamide local anesthetic that also contains an

ester group.

Biotransformation occurs in both the plasma

and liver ( hepatic microsomal enzymes)



AMIDE TYPE LOCAL

ANESTHETICS

Articiane has a vasodilating effect equal tothat of lidocaine.

pKa 7.8. pH of vasoconstrictor conating

solution 4.4 to 5.2. of 1:100,000, 4.6 to 5.4of 1:200,000.

Onset of action = 1-2 hrs.

Effective dental concentration 4% with

1:100,000 or 1:200,000 epinephrine. Half life = 0.5 hrs.

Maximum recommended dose 3.2 mg/lb or7mg/Kg. Maximum dose 600 mg.



AMIDE TYPE LOCAL

ANESTHETICS

Articaine is bale to diffuse through soft or

hard tissues more reliably than other local

anesthetics.

Articaine & prilocaine are the only local

anesthetic presently employed in 4%

concentration.

Articaine HCl with epinephrine iscontraindicated in person with known

sensitivity for amide type local anesthetics.



AMIDE TYPE LOCAL

ANESTHETICS

Articiane should be used with caution

in persons with hepatic disease and

significant impairment ofcardiovascular function.

Use in children under 4 yrs of age is

not recommended.



AMIDE TYPE LOCAL

ANESTHETICS

Bupivaicaine HCl: Amide. Prepared in1957, approved in oct 1972.

Potency : four times that of lidocaine,

mepivacaine and prilocaine. Toxicity less than 4 times that of lidocaine

and mepivacaine.

Vasodilating properties relatively

siginificant. pKa: 8.1; pH of plain solution 4.5 to 6.0; with

vasoconstrictor 3.0 to 4.5.



AMIDE TYPE LOCAL

ANESTHETICS Onset of action usually requires longer

onset of action ( 6-10 minutes) Dentalconcentration 0.5%.

Half life 2.7 hrs. Maximum recommended dose : 0.6 mg/lb

or 1.3 mg/kg body weight. A maximumdose of 90 mg can be given.

Two primary indications for its use:1) Procedure exceeding 90 minutes.

2) Management of post operative pain. Inpatients requiring post operative opiodanalgesics the dose is considerablylessened.



AMIDE TYPE LOCAL

ANESTHETICS For post operative pain control after lengthy

surgical procedure bupivacaine is administeredimmediately before the patients discharge fromthe office.

Since the onset of anesthesia is delayed inmany patients it is advisable to initiate theprocedure with more rapid acting anestheticslike articaine, mepivacaine or prilocainefollowed by bupivacaine for the duration offanesthesia.

Bupivacaine is not recommended in youngerpatients, physically handicapped and mentallydisabled persosn for the risk of post – operativetissue injury.

Rarely indicate din children because paediatric

dental procedures are usually of short duration.



AMIDE TYPE LOCAL

ANESTHETICS

Etidocaine HCl: Prepared – 1971.

FDA approved – 1976. Potency – 4

times that of lidocaine. Toxicity – 2times toxic than lidocaine.

When given subcutaneously 4 times

toxic.

When given rapid IV vasodilating

properties relatively significant.



AMIDE TYPE LOCAL

ANESTHETICS

Vasodilating properties relatively significant.

Pka 7.7. pH of plain solution is 4.5; withvasoconstrictor 3-3.5.

Onset of action – equivalent to that oflidocaine, mepivacaine, prilocaine (1 ½ to 3minutes)

Effective dental concentration 1.5%.

Half life 2.6 hours.

Maximum recommended dose 400 mgs.

Long acting local anesthetics likebupivacaine only differ in the onset ofaction.



ANESTHETICS FOR

TOPICAL APPLICATION

Concentration in typically greater than the

same administered by injection. Since they

don’t contain vasoconstrictors vascular

absorption is rapid.

As a rule topical anesthetics are effective

only on surface tissues eg- benzocaine,

liodcaine.

Spray devices that do not deliver “measured

doses” should not be used intra orally.



Eutectic Mixture of Local

Anesthetic (EMLA)

EMLA cream (lidocaine 2.5%, Prilocaine

2.5%) is an emulsion in which the phase is

a eutectic mixture of lidocaine and

prilocaine in a ratio of 1:1 by weight.

Supplied in a 5g or 30 g tube. Not indicated

in patients with congenital or idiopathic

methemoglobinemia & infants under 12.

Lidocaine available in two forms for topical

use lidocaine base 5%, Lidocaine 2%.

Tetracaine HCl: Long duration ester LA can

be injected or applied topically.



SELECTION OF A LOCAL

ANESTHETIC

The following factors to be considered:

1) Length of time for which pain control is

necessary.

2) The need for post treatment pain control.

3) The need for hemostasis.

4) Whether any contraindication exists for the

administration of the selected localanesthetic.

LOCAL ANESTHESIA



LOCAL ANESTHESIA

ARMAMENTARIUM FOR A

DENTIST Minimum two drugs is recommended –

Amides are prefered.

1) Short duration of pulpal anesthesia

(30mts).

2) Intermediate duration (approximately 60

mts)

3) Long duration ( 90 mts)4) Typical anesthetic for tissue preparation

before injecting LA.

clinical action of specific agents

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