Decreasing nerve transmission at the site of application provides limited, brief, local anesthetic effects. Temporary relief of discomfort and a dry, bloodless field for suturing is created by the combination of these three medications. Tetracaine inhibits initiation and conduction of nerve impulses at the site of application. Adrenaline causes vasoconstriction, decreasing the systemic absorption of medications, as well as reducing the flow of blood to the wound site, allowing for a dry tissue field to repair. Cocaine produces prolonged vasoconstriction and rapidly blocks initiation and conduction of nerve impulses where applied.
Tetracaine is a potent amino ester.
Esters are metabolized by plasma and liver cholinesterases. Effects of topical Tetracaine last about 45 minutes. Adrenaline is an aromatic amine. Topically applied, Adrenaline is taken up by adrenergic nerve endings and metabolized by enzymes in the liver and other tissues. Cocaine is a benzoic acid ester.