Epinephrine added to a solution of lignocaine for a peripheral nerve block will:: (A) Increase risk of convulsions, (B) Increase the duration of action of the local anesthetic, (C) Both (a) and (b), (D) None of these
Answer is B. (Ref: K DT 6/e p354) Adrenaline and felypressin are the vasoconstrictors that are added to LA solution. By causing vasoconstriction, these drugs - decrease the systemic absorption resulting in less CNS adverse effects (decreased chances of seizures). Prolong the stay of drug at the site of action resulting in the increase in duration of action of LA.