Validating a New Non-invasive Approach to Testing Lidocaine Effectiveness

In prior tests with a convenience sample, subjects who reported that they had no trouble getting numb at the dentist, also got numb with lidocaine gel on the surface of the tongue. That numbness prevented them from being able to taste any flavor until the numbness had worn off. Subjects who reported having trouble getting numb at the dentist, could still taste flavors after the application of lidocaine. This work will assess the reliability of a taste‐based approach for creating a non‐invasive way to test lidocaine effectiveness. The controlled trial will assess the ability of lidocaine oral gel to block taste (e.g., sweet) in 20 adults (ages 18‐49) half with history of trouble getting numb at the dentist (Arm 2) and half with no trouble (Arm 1). To determine reproducibility, the taste‐based test will be done 4 times on different days, twice with lidocaine and twice with a placebo, with randomization and double‐blinding. These repeated results will be compared to a fifth assessment, against the "gold standard" of injection of lidocaine, assessed using a dental probe. On each of four separate visits, in randomized order, the subject will be tested with tastants to the tongue twice after application of a lidocaine gel to the tongue and twice with a placebo gel. After a wait of two‐minutes, the three tastants will be tested. The subject is blinded to the taste and the identity of the gel, which have been compounded to look the same. On the fifth (last) visit, the subject will get an oral injection of lidocaine and the numbness assessed. The results across the five tests will then be analyzed. We are testing in separate studies NCT 03563573 and NCT 03676725 the prevalence of lidocaine ineffectiveness in those with Attention Deficit Hyperactivity Disorder (ADHD) and in the general population without ADHD. We believe the prevalence will be higher in ADHD. As a result, in this evaluation we have one Arm "gets numb at the dentist" where exclusion criteria includes ADHD and a second Arm "has trouble getting numb at the dentist" that does not have that exclusion.