Local Anesthetic Efficacy in Marijuana Users and Nonusers

Objectives: Achieving profound local anesthesia of adequate duration is essential to providing safe and comfortable dental treatment. There is a well-recognized clinical impression that patients with a history of drug abuse are difficult to anesthetize for dental treatment. However, literature on this clinical phenomenon is sparse, and there is no published research on local anesthetic efficacy in marijuana users. The objective of this pilot project was to assess if differences exist between marijuana users and nonusers in the ability to be anesthetized for dental treatment. Chronic effects of marijuana use were assessed, rather than acute.
Methods: Subjects were healthy adult males and females who qualified as non-marijuana users or heavy marijuana users. All subjects had an asymptomatic maxillary lateral incisor that responded to the electric pulp test (EPT). A standard maxillary infiltration injection technique was employed using 1.7 mL 2% lidocaine with 1:100,000 epinephrine over the test tooth. EPT testing was repeated every 3 minutes until the tooth regained responsiveness to the EPT, or testing was halted if anesthesia was not obtained within 18 minutes.
Results: Sixteen nonusers and 16 marijuana users completed the study. The mean onset of anesthesia was 3.94±0.53 minutes for nonusers and 5.63±1.19 minutes for users (mean±SEM, p>0.05). The mean duration of anesthesia was 31.3±3.68 minutes for nonusers and 26.1±3.86 minutes for users (mean±SEM, p>0.05).
Conclusions: Although there was a modest trend toward a delayed onset and shorter duration of local anesthesia in marijuana users compared to nonusers, the differences were not statistically significant. Studies with greater power may be useful to determine if a statistically or clinically significant difference exists within subgroups of users. Additionally, further research is needed to assess if differences occur in the presence of pulpal inflammation, as well as the acute effects of marijuana use on local anesthetic efficacy.