Adjuvants to local anaesthetics in regional anaesthesia – Should they be used? Part II: Cons

SummaryMany drugs used as adjuvants for peripheral nerve blocks may not potentiate the effect of local anaesthetics to produce a clinically significant effect. At times, the side effects caused by the systemic absorption of these drugs outweigh the benefits. Some drugs that have already been in use as adjuvants have subsequently been demonstrated to have neurotoxic potential in animals, but data in humans is lacking. The aim of this article is to bring forth all the available literature as regards the above features with respect to adjuvants such as opioids, clonidine, dexmedetomidine, ketamine, midazolam, magnesium, adenosine, neostigmine and epinephrine which are commonly used with local anaesthetics to enhance the effect of regional nerve blocks.