Effectiveness of Phentolamine Mesylate as a Reversing Agent for Local Anesthesia in Children

Local anesthesia is the most common method for pain control during any dental procedures, but it is also one of the factors that can trigger discomfort and anxiety in children. Local anesthetics are primarily used to reversibly block action potentials that create impulse conduction along neural axons carrying sensory or motor signals. This occurs by blocking voltage-gated sodium channels. A prospective study of 320 children by College et al., (2000), reported soft tissue trauma frequency as 18%, 16%, 13% and 7% in children who are; less than 4, 4-7, 8-11 and more than 12 years old, respectively following inferior alveolar nerve block anesthesia and its numbing effect. The search for a pharmacologic means of minimizing postoperative soft tissue anesthesia has focused on phentolamine mesylate (PM), where an injectable form has been developed. Following the administration of local anesthetic with vasoconstrictor, a subsequent phentolamine injection into the same location enhances the redistribution of the local anesthetic away from the injection site as it is an alpha-adrenergic blocking agent, explaining the more rapid return of normal intraoral and perioral sensation. An intra-oral preparation of PM for the reversal of soft tissue anesthesia was approved by the FDA in May 2008, to be used for patients \> 6 years of age and weighing \> 15 kg. Later, in March 2016, the FDA approved its use in pediatric patients 3 years and older. Dosage form of OraVerse (phentolamine mesylate) is 0.4 mg/1.7 ml solution per cartridge. Its maximum dose is 2 cartridges in adults. The first published placebo-controlled phase two study reported that, in 10- to 58-year-old dental patients, an injection of phentolamine, at a one-to-one ratio at the site of the previous injection of local anesthesia, accelerated median recovery time to normal sensation of the upper and lower lips by 85 minutes.