Which of the following represents the concentration of adrenaline which is used with lidocaine ?

Lidocaine stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of nerve impulses, thereby effecting local anesthetic action. Epinephrine, in concentrations of 5 mcg/ml, is commonly used to decrease the absorption of local anesthetics. A 5 mcg/ml (1:200,000) dose of epinephrine will significantly reduce the peak blood levels of lidocaine and mepivacaine regardless of the site of administration. Epinephrine does not affect the vascular absorption of etidocaine and bupivacaine in the epidural space. However, the addition of epinephrine does significantly reduce the vascular absorption of etidocaine and bupivacaine when utilized for peripheral nerve blocks. Benefits of decreased absorption include increased neuronal uptake, enhanced quality of analgesia/anesthesia, prolonged duration of action, and decreased risk of toxicity. A concentration of 1:200,000 (5 mcg/ml) is commonly used for peripheral nerve blocks to reduce vascular absorption.