Chapter 8: Topical Anesthetics

The risk of methemoglobinemia is most linked to ___________, especially 20% sprays.

Benzocaine

How does benzocaine potentially cause methemoglobinemia?

Converts hemoglobin to methemoglobin, which cannot carry oxygen

Which groups are at an increased risk of methemoglobinemia?

Infants, young children, older adults, and those with G6PD deficiency

How long does it take for methemoglobinemia to develop?

Minutes to hours after application of a topical

What are the typical signs of methemoglobinemia?

Cyanosis unresponsive to oxygen, shortness of breath, and fatigue

What are severe signs of methemoglobinemia?

Confusion, arrhythmias, seizures

What is the treatment for methemoglobinemia?

Methylene blue in medical setting

What are the preventative methods for methemoglobinemia?

Use minimal amount of topical and avoid benzocaine in high-risk patients

True or False: Topical generally has a greater concentration of LA than injectable.

True

True or False: Topical anesthesia contains vasoconstrictors.

False

How far into the mucous membrane is topical anesthesia effective?

Only 2 to 3mm

Topical anesthetics in _____________________ make it difficult to control the amount expelled and to confine it to the desired site.

Pressurized spray containers

What agents are commonly in topicals?

Benzocaine ester, Butacaine sulfate, Dyclonine hydrochloride, Lidocaine, Tetracaine hydrochloride

Which type of topical is described:

-Most frequently used

-20% concentration

-Ester

-Duration 5 to 15 minutes

Benzocaine

Which type of topical is described:

-Most potent, therefore potentially toxic

-2% concentration

-Ester

-Duration 20 to 40 minutes

Tetracaine

Which type of topical is described:

-Amide

-5%

-2 to 3 minutes for onset and full 5+ minutes for full effectiveness

-Duration 15 minutes

Lidocaine

Which type of topical is described:

-2.5% lidocaine and 2.5% prilocaine

-Oraqix only formation of this approved for dental in the US

-Onset 30 seconds and duration 15-30 minutes

EMLA- Eutectic Mixture of LA

What agents are used in surface anesthetic preparations?

Benzocaine or ethyl aminobenzoate (ester type)

Tetracaine HCL (Ester)

Lidocaine, lidocaine HCL (Amide)

Lidocaine: Transoral patch

Eutectic mixtures have which of the following characteristics?

Their formulations facilitate deeper and more efficient penetrations of tissues compared with their ingredients acting alone.

Which of the following lists is most accurate when describing topical anesthetic uses?

All of the above

Which one of the following statements is incorrect regarding maximum recommended doses of topical anestheics?

Spray forms have easy-to-track dosing

Generous quantities of topical and injected anesthesia have been administered, when the patient begins to shake and appears agitated and anxious. Is there a reason for concern?

Yes, because these may be early signs of CNS depression

Topical anesthetic mixtures may be of benefit in all but which one of the following ways?

Mixtures decrease the potential for adverse reactions

All of the following statements are true regarding compounded drugs, except:

Compounded drugs may be used on other individuals as long as the use is the same as the original use.

The predominantly base form of lidocaine topical anesthetic is safer than the predominantly hydrochloride salt.

True

Dyclonine hydrochloride is an excellent and very durable topical anesthetic and belongs to which one of the following classes of anesthetic?

Ketone