Warnings regarding cocaine as a topical anesthetic

Various anesthetic mixtures that contain cocaine have been used to anesthetize minor skin lacerations, especially on the face or scalp. One such combination that is extemporaneously prepared by hospital pharmacies includes tetracaine 0.5%, epinephrine (Adrenaline) 1:2000, and cocaine 11.8%. This combination is commonly referred to as TAC solution. Its use results in decreased pain on application and may provide better patient tolerance of suturing, particularly in those who are unable to tolerate injections or who have difficulty following instructions or sitting still (eg, children, individuals with mental disabilities). However, serious toxic effects (eg, seizures, cardiac death) have been described following topical cocaine application, particularly in infants and children.  Because of increased toxicity, expense, and federal regulatory issues, cocaine is no longer recommended for topical anesthesia.

Compounded mixtures such as lidocaine, epinephrine, tetracaine (LET) solutions, have replaced cocaine with lidocaine 4% because of their superior safety when applied to nonintact skin. Still, these solutions should not be applied to wounds with end-arteriolar blood supply.

Allergic reaction to local anesthetics

Actual hypersensitivity is rare and accounts for less than 1% of all reactions to local anesthetics. Allergic reactions may be attributed to other factors such as acute toxicity, concurrent drug therapy (eg, tachycardia caused by epinephrine), or preservatives, such as paraben or sulfites, that the product may contain.

Local anesthetics with a para -amino benzoic acid (PABA) ester-type structure seem to cause most anesthesia-related allergic reactions. Consequently, use esters (eg, tetracaine, benzocaine) with caution or use a topical anesthetic from the amide class (eg, dibucaine, lidocaine). Documented cross-sensitivity has been exhibited within the ester-based local anesthetics and structurally related compounds (eg, paraben preservatives). Hypersensitivity to the amide local anesthetics is rare. To quickly determine whether an anesthetic agent is an ester or an amide, note whether the generic name contains the letter i once or twice. Esters contain the letter i once in their generic names, whereas the generic names for amides contain the letter i twice.

Physiochemical variables

Onset of action, anesthesia depth, and duration of action are determined by the pKa level, pH level, lipid solubility, protein binding, and vasodilatory effects of the specific local anesthetic. These factors also depend on the area of the skin to which the anesthetic is applied, the vascularity of tissues, the surface area, and anesthesia technique. Duration of application is important to improve topical anesthetic properties.

Table 2. Common Topical Anesthesia

Anes-thetic Class Generic Name (Trade Name) Available/ Recom-

mended Concent-

ration(s), %*

Dosage Form(s) Max. Adult Topical Dose, mg Max. Adult Mucosal Dose, mg Max. Pediatric Mucosal Dose, mg/kg Peak Effect, Minutes Duration, Minutes
Amides Dibucaine (Nupercainal) 1 Cream, ointment 25 -- -- <5 30-60
  Lidocaine (Xylocaine, ELA-Max, Lidoderm) 2-5 Viscous jelly, patch, ointment, liposomes Variable depending on dosage form 250-300 3-4 2-5 Liposome: 30 15-45
Esters Benzocaine

(Americaine, Cetacaine, Dermoplast, Solarcaine)

0.5-20 Aerosol, cream, gels, lotion, ointment, solution -- -- -- <5 15-45

 

Cocaine † 4-10 Solution 200 1 mg/kg 1 1-5 30-60

 

Tetracaine

(Pontocaine)

0.5-2 Solution, gel, cream 50 20 0.75 3-8 30-60
Misc. Dyclonine

(Cepacol, Sucrets)

0.5-1 Aerosol, lozenge -- 50 -- <10 <60
  Pramoxine

(ProctoFoam, Caladryl Cream for Kids)

1 Aerosol foam, pledgets, cream, ointment 200 -- -- 3-5 --
  Lidocaine/

Prilocaine

(EMLA)

2.5/2.5 Cream,

trans-

dermal patch

1 g/10 cm2 -- -- 60: 3 cm depth

120: 5 cm depth

30-60 after removal
  Lidocaine 70 mg and tetracaine 70 mg (Synera Patch) -- Trans-

dermal

patch

Adults or children:

Apply 1 patch 20-30 min before superficial dermato-

logical procedure

-- -- 100 --
Anes-thetic Class Generic Name (Trade Name) Available/ Recom-

mended Concent-

ration(s), %*

Dosage Form(s) Max. Adult Topical Dose, mg Max. Adult Mucosal Dose, mg Max. Pediatric Mucosal Dose, mg/kg Peak Effect, Minutes Duration, Minutes
Amides Dibucaine (Nupercainal) 1 Cream, ointment 25 -- -- <5 30-60
  Lidocaine (Xylocaine, ELA-Max, Lidoderm) 2-5 Viscous jelly, patch, ointment, liposomes Variable depending on dosage form 250-300 3-4 2-5 Liposome: 30 15-45
Esters Benzocaine

(Americaine, Cetacaine, Dermoplast, Solarcaine)

0.5-20 Aerosol, cream, gels, lotion, ointment, solution -- -- -- <5 15-45

 

Cocaine † 4-10 Solution 200 1 mg/kg 1 1-5 30-60

 

Tetracaine

(Pontocaine)

0.5-2 Solution, gel, cream 50 20 0.75 3-8 30-60
Misc. Dyclonine

(Cepacol, Sucrets)

0.5-1 Aerosol, lozenge -- 50 -- <10 <60
  Pramoxine

(ProctoFoam, Caladryl Cream for Kids)

1 Aerosol foam, pledgets, cream, ointment 200 -- -- 3-5 --
  Lidocaine/

Prilocaine

(EMLA)

2.5/2.5 Cream,

trans-

dermal patch

1 g/10 cm2 -- -- 60: 3 cm depth

120: 5 cm depth

30-60 after removal
  Lidocaine 70 mg and tetracaine 70 mg (Synera Patch) -- Trans-

dermal

patch

Adults or children:

Apply 1 patch 20-30 min before superficial dermato-

logical procedure

-- -- 100 --

*Use lower concentrations for children or patients who are elderly or debilitated.

† Cocaine is generally not recommended for topical or mucosal application (see warnings above).

‡ This dose also applies to the pediatric population (maximum application time in children aged <3 mo = 1 h; >3 mo = 4 h).

Source emedicine.medscape.com

 

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