DOUBLE-BLINDED COMPARISON OF DIPHENHYDRAMINE VERSUS LIDOCAINE AS A LOCAL-ANESTHETIC

Study objective: To evaluate the efficacy, onset of action, duration o f action, and side effects of 1 % diphenhydramine compared with 1 % li docaine when used as a local anesthetic agent. Design: Prospective, do uble-blinded, cross-over study, Setting: Emergency medicine residency program, research section. Participants: Ten healthy male volunteers, aged 26 to 38 years old. Interventions: Baseline levels of sensation t o pinprick (18-gauge needle) within a 2.4-cm-diameter midvolar forearm area and levels of sedation were recorded on 10.2-cm visual analog sc ales. Subjects then underwent subcutaneous infiltration of 20 mg (2 mL ) of the study agent using a 27-gauge needle. Visual analog scale sens ation and sedation scores were recorded at five, ten, and 15 minutes a nd then every 15 minutes until return to baseline. Subjects were studi ed one week later with the alternate agent. Nonparametric data were an alyzed using the Mann-Whitney U test with significance at P < .05. Res ults: No significant differences in mean pinprick sensation were seen from baseline to 30 minutes. Significant differences were seen at 45 ( P = .036) and 60 minutes (P =.036). The mean duration of effective ane sthesia was significantly longer for lidocaine than diphenhydramine (8 1 versus 42 minutes, P = .028). No significant differences were seen i n the sedation scores or in the frequencies of local reactions. One su bject developed skin necrosis at the injection site with diphenhydrami ne. Conclusion: The duration of local anesthesia for 1 % lidocaine was significantly longer and the depth of anesthesia after 30 minutes was significantly higher than that of 1 % diphenhydramine. Diphenhydramin e resulted in skin necrosis in one test subject.