A study of benzocaine gel dosing for toothache

This pilot study evaluated subject compliance with a proposed OTC label with improved dosing directions for self-application of a 20% benzocaine gel for toothache pain, and assessed the methodology for evaluating efficacy in a future pivotal study of benzocaine gel. It was hypothesized that > or = 75% of subjects would apply < or = 400 mg of product (80 mg benzocaine). Exploratory analyses of efficacy were also performed.

Thirty patients with spontaneous pain of moderate or severe intensity from a single tooth due to caries, a lost restoration, or a fracture entered this randomized, parallel group, double-blind study. Before self-applying 20% benzocaine gel or placebo, patients read a label containing new dosing directions, including a picture of how much product to apply to their tooth and the surrounding gingival tissues. The amount applied was determined by weighing the tube before and after dosing. Following dosing, pain intensity and relief were recorded every five minutes through 30 minutes, then every ten minutes through 120 minutes. Responders were defined as those subjects who experienced at least a one-unit reduction in pain intensity from baseline at two consecutive time points within the first 20 minutes. Onset of meaningful relief was recorded using a stopwatch. The percentage of responders was compared using the Mantel-Haenszel test. ANOVA was employed to test for differences in Pain Relief Combined with Pain Intensity Difference (PRID), and the areas under the curve at 30, 60, 90, and 120 minutes for this measure (SPRID). Median onset and duration times were compared using the Cox proportional hazards model. Adverse events were recorded if and when they occurred.

It was found that 86.7% of the subjects (26/30) applied < or = 375 mg of product (mean +/- SD = 327.7 +/- 276.8 mg). The benzocaine group had a significantly higher (p = 0.022) responder rate (86.7%) than the placebo group (46.7%). Significant differences in favor of the benzocaine group were also recorded for PRID at 10, 15, and 30 minutes (p < 0.05) and SPRID-30 (p = 0.037). Median onset and duration times were 8.3 minutes and > 115 minutes for the benzocaine group, >120 minutes and 5 minutes for the placebo group. There were no adverse events recorded in the study.

The improved dosing directions resulted in a high percentage of subjects self-applying an appropriate amount of benzocaine gel or matching placebo. The label and study methodology appear suitable for a pivotal dose-response study in subjects with toothache pain. While the current study was not statistically powered to make firm efficacy conclusions, 20% benzocaine gel appeared more efficacious than placebo, providing a rapid onset of pain relief and a relatively long duration of action.