DIPHENHYDRAMINE
FOR THE PREVENTION OF AKATHISIA INDUCED BY PROCHLORPERAZINE: A RANDOMIZED,
CONTROLLED TRIAL
Vinson
DR, Drotts DL. Ann Emerg Med. February 2001;37:125-131.
STUDY
OBJECTIVES: The utility of intravenous prochlorperazine as an antiemetic agent
and abortive therapy for headache may be limited by the frequent occurrence of
akathisia, the distressing effects of which have been shown to disrupt patient
care. We tested the hypothesis that adjuvant diphenhydramine reduces the
incidence of akathisia induced by prochlorperazine.
METHODS:
This randomized, double-blind, placebo-controlled trial was conducted in the
emergency department of an academic tertiary care medical center with an annual
census of 95,000 emergency patient visits. We enrolled a convenience sample of
100 adult patients who received 10 mg of intravenous prochlorperazine for the
treatment of nausea/vomiting or headache. Subjects were randomly assigned to
receive a 2-minute infusion of prochlorperazine with either 50 mg of diphenhydramine
or placebo. The incidence of akathisia at 1 hour was measured by using explicit
diagnostic criteria. To measure the influence of treatment on sedation, the
subjects noted, on a 100-mm visual analog scale, their degree of sedation
before and after treatment.
RESULTS:
Akathisia developed in 18 (36%) of 50 subjects in the control group and in 7
(14%) of 50 subjects in the diphenhydramine group, a 61% relative reduction.
The addition of adjunct diphenhydramine resulted in an absolute reduction of 22%
in the incidence of akathisia (95% confidence interval [CI] 6% to 38%; P=.01).
The odds ratio for akathisia with the use of adjuvant diphenhydramine was 0.39
(95% CI 0.18 to 0.85). Mean sedation scores increased 12 mm after infusion of
prochlorperazine alone (95% CI 3 to 21 mm) compared with a 33-mm increase after
infusion of prochlorperazine with adjuvant diphenhydramine (95% CI 24 to 42
mm). The 12-mm difference between the groups was statistically significant (95%
CI 9 to 34 mm, P<.001).
CONCLUSION:
Adjuvant diphenhydramine reduces the incidence of akathisia induced by
prochlorperazine and is associated with an increase in sedation.