ANESTHETICS

1. What is meant by a 2% solution of Lidocaine (Xylocaine)?

% = weight/volume, where 100% = density of water = 1 g/ml

thus, 1% = 1gm/100ml (or 1g/dl) = 0.01g/ml = 10 mg/ml = 1 gram %

(1 mg % = 10 g/ ml, but if it is not specified, we assume gram % is the percentage that the manufacturer is referring to)

2. What is the molarity of 2% Lidocaine solution?

Molecular weight (mw) of lidocaine = 234 Daltons (Da)

Thus, 1 mole = 234 grams 1 mole = 6 x 10²³ molecules

In a 2% solution, 20mg/ml = 20 g/L

20 g/ (234g/mol) = 0.085 mol

0.085 mol/L = 85 mM

3. How many carpules of 2% Lidocaine without epinephrine can be injected into a healthy 150 lb adult male? for an adult male weighing 150 lbs? (MRD = Maximum Recommended Dosage for healthy adults)

MRD for 2% Lidocaine without epinephrine = 4.5 mg/kg, not to exceed 300 mg

step 1.) Change pt weight from lb kg.

150lbs = 150lb/ (2.2 lb/kg) = 68 kg

step 2.) How many mg can be injected?

4.5 mg/kg x 68 kg = 306 mg

thus, the max that can be injected is 300 mg

step 3.) 2% solution = 20 mg/ml, 300mg/ (20 mg/ml) = 15 ml

step 4.) Convert to amount in carpules.

Each carpule = 1.8 cc; 15cc/ (1.8cc/carp.) = 8.3 carpules

Category: Pharmacology Notes