Factors Affecting Plasma Levels of Lignocaine and Prilocaine

Abstract

Plasma levels of local anaesthetics following their injection are affected by many factors. Serial plasma levels following injection of lignocaine and prilocaine at various rates in over 500 patients have been measured and this has allowed some of these factors to be assessed and quantified. The vascularity of the site of injection causes major differences in the maximum plasma level. Prilocaine consistently gives lower levels than lignocaine. Adrenaline causes a reduction in the plasma levels of both drugs and the optimal concentration is 1:200,000. Speed of injection is important when giving the drugs intravenously but not epidurally. The concentration of the injected solution does not affect the plasma levels. The weight and age of the patients (all adult females) were unrelated to the mayi'mnm plasma levels.

Local Anesthetics: Review of Pharmacological Considerations

“…Additional variables were also addressed by Scott et al 4 As expected, the dosage and speed of injection were directly related to serum concentration. A solution's concentration, eg, 2 versus 4%, was not relevant; serum concentrations were related to the total dosage.…”

“…In 1972, Scott et al published one in a series of landmark clinical studies assessing variables that determine subsequent concentrations of lidocaine and prilocaine in serum. 4 It is not surprising that serum concentrations were found to vary according to the relative vascularity of the tissues in which the anesthetic was injected. Using lidocaine 400 mg, the highest serum levels illustrated in Figure 4 followed infiltration of vaginal mucosa and the lowest followed subcutaneous abdominal infiltration.…”

Neuromuscular blockade in infants following intramuscular succinylcholine in two or five per cent concentration

“…It has been established that the plasma concentration of lidocaine after intramuscular injection is related to the total dose administered and not to the concentration of the injected solution. 16,17 The pattern of neuromuscular blockade during the onset of block in the infants was of the depolarizing type with depression, and later recovery, of T1.18 However, train-of-four fade was demonstrated in all of the patients to a certain extent. In a quarter there was some fade of the control train during halothane anaesthesia.…”

Beyond a Simple Anesthetic Effect: Lidocaine in the Diagnosis and Treatment of Interstitial Cystitis/bladder Pain Syndrome

“…49 Mild toxicity is felt as a ringing in the ears and perioral numbness when lidocaine levels exceed 5 mcg/mL. The dose for lidocaine that reliably produces serum levels in the safe range of 1-3 mcg/mL are 1-1.5 mg/kg intravenously and 4-5 mg/kg when infiltrated into tissue.…”