Topical Anesthetics

Can not penetrate intact skin More effective if not water soluble Higher concentrations than injectables Can cause toxicity

Topical Anesthetics Concentrations are higher to facilitate diffusion; leads to a greater potential for toxicity Many injectables are not used as topical because their effective concentrations would be toxic

Topical Anesthetics Only penetrate 2-3 mm, on mucous membranes or disrupted skin Smallest effective quantities, since rapidly absorbed into systemic circulation

Cocaine Hydrochloride Water soluble ester, 2-4% for topical use Vasoconstrictive, potentiates adrenalin which may result in dysrythmias Onset - 1min; duration - up to 2 hrs Schedule II drug, not recommended for use in dentistry

Benzocaine Ester, poorly soluble in water Available as spray, gel, ointment % Poor CV absorption, little risk of toxicity Remains at site, increased duration Possible localized allergic reactions Can inhibit sulfonamides

Lidocaine Hydrochloride Amide, 2% solution Water soluble Better penetration, greater toxicity than base Low incidence of allergic reaction

Lidocaine Base Poor water solubility 5% liquid, ointment, gel Poor penetration, best on ulcerated, lacerated, or abraded tissue Low incidence of allergic reaction

Dyclonine Hydrochloride Ketone, no cross-sensitization Slight water solubility, low toxicity Slow onset -to 10 mins; long duration -to 1 hr 0.5% solution

Butacaine Sulfate Topical for eyes, ears, nose, throat Substitute for Cocaine 2X as potent, 2X as toxic 2X as potent, 2X as toxic 4% dental ointment

Tetracaine Hydrochloride Ester, highly soluble in water Potency - 5-8X Cocaine, great potential for systemic toxicity 2% liquid

Short Duration-5-40mins Without vasoconstrictors Lidocaine 2% Lidocaine 2% Prilocaine 4% Prilocaine 4% Mepivacaine 3% Mepivacaine 3%

Intermediate Duration-45-90mins With vasoconstrictors Lidocaine 2% with epi Lidocaine 2% with epi Mepivacaine 2% with epi or levonordefrin Mepivacaine 2% with epi or levonordefrin Prilocaine 4% with epi Prilocaine 4% with epi

Long Duration->90mins With vasoconstrictors Bupivacaine 0.5% with epi Bupivacaine 0.5% with epi Etidocaine 1.5% with epi Etidocaine 1.5% with epi

Maximum Dosage Calculated by body weight (mg/kg or lb) Arbitrary maximum usually approximately at average adult weight of 70 kg Decrease in very young, elderly, debilitated, or medically compromised

Contraindications - Absolute Med problem Avoid May use Anesthetic same class different class allergy allergy Bisulfite vasoconstrict. non-constrict. allergy anesthetics types allergy anesthetics types Sulfur Articaine non-sulfur allergy types allergy types

Contraindications - Relative Med problem Avoid May use Atypical esters amides cholinesterase Methemo- Prilocaine, others globinemia Articaine globinemia Articaine Liver disease amides esters, or amides (severe) judiciously (severe) judiciously

Contraindications - Relative (cont.) Med problems Avoid May use Kidney disease amides & either (severe) esters judiciously (severe) esters judiciously CV disease excess plain or (severe) vasoconstrictor decrease amt (severe) vasoconstrictor decrease amt Hyperthyroid excess plain or (severe) vasoconstrictor decrease amt (severe) vasoconstrictor decrease amt

Selection of an Anesthetic Duration required for treatment Posttreatment discomfort Possibility for self-inflicted injury Need for hemostasis Patient’s medical status

Two or more anesthetics ? Maximum total dose The total allowable dose for both local anesthetics should not exceed the lower of the two maximum doses for the individual agents. The total allowable dose for both local anesthetics should not exceed the lower of the two maximum doses for the individual agents.