Topical Anesthetics

In general, the concentration of topical anesthetic is ________ than if that same drug were to be used as an injectable drug

higher (this facilitates diffusion)

Some topicals are preserved using _________, which is banned from injectable use.

parabens (preservatives can cause allergic rxns)

T or F? Conventional topical anesthetics cannot diffuse through intact skin, but are useful on mucous membranes

TRUE!

Topical anesthetics are effective only on _______________.

surface tissues (2-3mm)

What are the main uses of topical anesthetics?

1. allow atraumatic needle penetration of the mucous membranes

2. relief of discomfort during: radiographic film placement, periodontal evaluation and treatment, placement of retraction cords and rubber dams, superficial manipulation of mucosal tissues.

What are factors that affect topical anesthetic toxicity?

1. Concentration

2. Ability to penetrate tissue

3. Speed of systemic absorption

4. Total area of coverage

When can local adverse rxns to topical anesthetic occur?

when anesthetic is applied to abraded tissue, for extended periods of time, or when there is an undiagnosed hypersensitivity to a particular agent.

What are some examples of local adverse reactions at the site of application of topical?

- Sloughing

- Edema

- Delayed hypersensitivity

- Redness

- Pain

- Burning

Does swallowing topical anesthetic have any harmful effects?

NO significant systemic uptake occurs during swallowing of anesthetic. Locals are not readily absorbed by the GI mucosa

What are the 4 topical anesthetic drugs?

benzocaine, lidocaine, tetracaine, dyclonine

The allergen responsible for allergic reactions in ester anesthetics is ________.

PABA (esters produce this when metabolized, but amides do not)

__________ is insoluble in water, and therefore slowly absorbed into the CVS, and less likely to produce an overdose reaction.

BENZOCAINE

Benzocaine is also known to cause ______________, similar to prilocaine

methemoglobinemia

Which topical anesthetic is nonester, nonamide, and ketone? (when both ester and amide anesthetics (benzocaine and lidocaine) cannot be used)

Dyclonine HCl

Topical Lidocaine is available in 2 formulations, which are ...?

1. Lidocaine base at 5% concentration

2. Lidocaine HCl at 2% concentration

Which formulation of topical lidocaine is WATER SOLUBLE?

Lidocaine HCl at 2% concentration - penetrates tissue more effectively BUT higher risk of toxicity

Which formulation of topical lidocaine is indicated for use on ulcerated, abraded, or lacerated tissue?

Lidocaine base at 5% concentration

Which topical anesthetics have the SLOWEST onset times, but also LONGEST duration of action?

dyclonine and tetracaine

Tetracaine HCl is mainly used at a _____% concentration for topical purposes.

2%

(very potent and can lead to serious adverse rxns)

________ has a slow onset, peaking only at 20 minutes but lasting for up to 1 hour.

Tetracaine

T or F? Topicals are occasionally packaged in combination to optimize anesthetic properties such as onset and duration.

TRUE - One example of an effective combination is of lidocaine and prilocaine. This combination is called a eutectic mixture.

What is EMLA?

Eutectic Mixture of Local Anesthetics. Lidocaine with prilocaine. Topical anesthetic used in dentistry that is also effective on intact skin

What is the onset time and duration of action for EMLA?

-onset time of 5-10 minutes

-peaks at 2-3 hours after application on skin

-lasts for 1-2 hours after removal from skin.

What is Oraqix?

- liquid that turns into gel when applied subgingivally

- placed in pockets

- *2.5% lido 2.5% prilo*

- 20-40% is absorbed systemically

- 1 min onset time

- duration average of 20 mins

- plastic safety collar covering the needle end so it can't accidentally be used as injectable anesthetic.