Lidocaine hydrochloride

Its very important to be able to recognize this molecule. The maximum systemic blood level after injection occurs at 10 minutes without vasoconstrictor, and at 60 minutes with vasoconstrictor... so you must be alert for toxic responses of your injection up to one hour after injection

Metabolism of Lidocaine

Lidocaine (2-diethylaminoacet-2',6'-xylidide) is broken down to several endproducts that are eventually excreted by the kidneys (KNOW THE ENDPRODUCTS!!):

-acetate

-ethylaminoacetic acid (monoethyl glycine) (MX or GX)

-4-hydroxy-2,6-DMA

-N-hydroxy-2,6-DMA

-2-amino-3-methyl-benzoic acid

*also, know each "in-between" product as outlined on this page and p.9 or the "regular handout"

Some pts experience sedation with lidocaine, probably due to the MEGX and MX metabolites; some metabolites are thus active!

Lidocaine is the only amide LA that can be used also as a topical anesthetic.

MRD for Lidocaine (2% Xylocaine)

The Maximum Recommended Dose (MRD) for normal, healthy adults (NOT elderly or young children or very sick pts) is:

-"Plain" (Lidocaine without epi): 4.5mg/kg (2.0 mg/lb) with a 300 mg MAXIMUM

DOSAGE regardless of weight (8 carps)

-Lidocaine with 1:100,000 epi: 7.0 mg/kg (3.2 mg/lb) with a 500 mg MAXIMUM

DOSAGE regardless of weight (14 carps)

(The Council on Dental Therapeutics recommends never going over 8 carps, regardless of the MRD values for lidocaine with epi).

**You must know MRD and be able to convert to mg and carpule equivalents... remember that there are different MRDs for lidocaine with and without epinephrine.

Category: Pharmacology Notes