Author: Cardiac Anesthesiologist
A number of local anesthetic formulations are available for topical anesthesia , lidocaine, dibucaine, tetracaine, and benzocaine being the drugs used most commonly. In general, these preparations provide effective but relatively short durations of analgesia when applied to mucous membranes or abraded skin. Their efficacy is determined by drug form, melting point, concentration, and skin permeability. Lidocaine and tetracaine sprays are commonly used for endotracheal anesthesia before intubation or for mucosal analgesia for bronchoscopy or esophagoscopy.
Topical anesthesia through cut skin is commonly used in pediatric emergency departments for liquid application into lacerations that require suturing. Historically, this had been provided by a mixture of tetracaine, epinephrine (adrenaline), and cocaine, known as TAC. TAC is ineffective through intact skin; in contrast, its rapid absorption from mucosal surfaces can lead to toxic, even fatal reactions. Another potential substance is ELA-max, a liposomal formulation of lidocaine which is useful for cuts or abrasions. Lastly, Lidoderm patches have been in use for the topical treatment of postherpetic neuralgia.
Because of concerns regarding cocaine toxicity and the potential for diversion and abuse, cocaine-free topical preparations are strongly recommended, and alternatives such as the combination of an α1-adrenergic agonist (oxymetazoline or phenylephrine) and a local anesthetic such as 2% to 4% lidocaine should be used, with more dilute solutions being recommended for infants and children.