Pharmacology of Local Anesthetics: Clinical Implications
Reversal of Soft-tissue Anesthesia

Epinephrine and levonordefrine are α₁-adrenergic-receptor agonists. They delay the uptake of LAs into the vascular compartment and contribute to prolonged soft-tissue anesthesia, i.e., anesthesia of the lip and tongue, and associated functional deficits.⁴⁵ Phentolamine mesylate, 0.4 mg in 1.7 mL cartridges (OraVerse^™, Novalar Pharmaceuticals) is a non-selective α₁-adrenergic-receptor antagonist. When injected at the site of LA administration, it shortens post-treatment duration of soft-tissue anesthesia.⁴⁵

Studies concluded that phentolamine mesylate administered at the same volume and at the same site as a LA with a vasoconstrictor significantly and safely reduces the duration of soft-tissue anesthesia and associated functional deficits.^46-48 However, its use is not approved by the FDA in children under the age of 6 years or in children who weigh less than 33 lbs. (15 kg). Clinicians should also consider the risks/benefits of reversal when a longer period of postoperative pain is anticipated.