Dj. Dire et De. Hogan, DOUBLE-BLINDED COMPARISON OF DIPHENHYDRAMINE VERSUS LIDOCAINE AS A LOCAL-ANESTHETIC, Annals of emergency medicine, 22(9), 1993, pp. 1419-1422
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.