LET solution consists of lidocaine HCl USP 4%, epinephrine bitartrate USP 180 mg, and tetracaine HCl USP 500 mg, with sodium metabisulfite 75 mg in sterile water for irrigation USP to 100 mL. It was described as a replacement for the problematic, traditional, cocaine-containing TAC solution by Schilling et al in 1995 (Schilling CG, Bank DE, Borchert BA, Klatzko MD, Uden DL.Tetracaine, epinephrine [adrenalin], and cocaine [TAC] versus lidocaine, epinephrine, and tetracaine [LET] for anesthesia of lacerations in children. Ann Emerg Med 1995;25:2:203-208).
The authors found "?no statistical difference between TAC and LET in adequacy of anesthesia before suturing or in duration of anesthesia during suturing."This result led them to conclude that LET could replace TAC effectively in the emergency room for use while suturing uncomplicated lacerations.The use of this formulation can reduce patient exposure to cocaine and can reduce costs and security risks for the institution.
One institution gives a formulation for this compound as follows:
Lidocaine HCl USP - 4000 mg
Epinephrine bitartrate USP - 180 mg
(55% epinephrine, 45% bitartrate)
Tetracaine HCl USP - 500 mg
Sodium metabisulfite - 75 mg
Sterile water for irrigation - qs ad 100 mL
-lace powdered ingredients in graduated cylinder and add water to 100 mL.
-f a sterile solution is desired, pass through a 0.2 micron filter.
-ET is a clear solution.
-tore in a light-resistant container.
-odium metabisulfite is added to improve the stability of epinephrine?
Stability: 6 months refrigerated, 4 weeks room temperature.[*] Discard if solution discolors.
A gel form of TAC can be made by adding 150 mg of methyl-cellulose 4000 cps to 3 mL of LET solution. Stir the combination for 2-3 minutes or until the solution becomes a gel. Use immediately after preparation." *Stability studies are not referenced. It would be prudent to adhere to the USP monograph Pharmacy Compounding <795> guideline for beyond-use dating of compounded products. Water-containing compounded products prepared should receive beyond-use dating not later than 14 days stored at cold temperatures.
References are available on request.
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