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Source: Ernst AA, et al. Prochlorperazine versus promethazine for uncomplicated nausea and vomiting in the emergency department: A randomized, double-blind clinical trial. Ann Emerg Med 2000;36:89-94.
Vomiting associated with gastroenteritis or gastritis is a major problem confronting emergency department (ED) physicians. Opinions vary as to which agent best controls vomiting and avoids undesirable side effects and unnecessary expense. Physician preference often is arbitrary rather than scientific. Ernst and colleagues compared intravenous prochlorperazine (Compazine) and promethazine (Phenergan) in a randomized, double-blind trial involving 84 adult patients from two academic EDs. All cases involved acute nausea and vomiting (with or without diarrhea), inability to tolerate oral fluids, and some degree of volume contraction as judged by ED physicians. Patients with focal abdominal pain, underlying serious illness, bowel obstruction, altered sensorium, alcohol abuse, pregnancy, or complicated etiology for vomiting were excluded.
A 100 mm visual analog scale (VAS) was utilized to assess symptom severity at baseline and at 30 and 60 minutes to rate adequacy of relief over time. Forty-two patients received either 10 mg of prochlorperazine or 25 mg of promethazine intravenously, along with appropriate fluid therapy (1.1-3 L). Demographics included an average age of 29 years (18-44); 70% were female; 60% were white. The average number of vomiting episodes was 7.3 (2-16) in 24 hours; 55% of patients had concomitant diarrhea.
At 30 and 60 minutes, VAS symptom ratings for prochlorperazine were significantly better than for promethazine (20 vs 46 mm, P = 0.004; and 4.5 vs 26 mm, P < 0.001, respectively). Complete relief at 30 minutes was achieved in 33% of prochlorperazine patients compared to 16% of promethazine recipients (P = 0.02). Only 16% of patients required 60 minutes to achieve full relief with prochlorperazine, compared to 36% of those receiving promethazine. Four (9.5%) patients in the prochlorperazine group required additional anti-emetic therapy and were deemed "treatment failures" compared to 13 (31%) promethazine patients (P = 0.03). Of those given prochlorperazine, 38% experienced drowsiness, compared to 71% of those receiving promethazine (P = 0.002). Six patients in each group had akathisia, reversible with diphenhydramine.
Both of these agents are phenothiazines, active as dopamine D2 receptor antagonists and frequently used for nausea and vomiting. Yet physician preference, not data, often dictates therapy. This trial demonstrates clinical and statistical advantages for prochlorperazine in ED patients with acute nausea, vomiting, and apparent volume contraction. Prochlorperazine convincingly outperformed promethazine in every category assessed: time to complete relief (twice as fast), more complete relief (twice as good), fewer clinical failures (one-third as many), and less sedation (one-half as often).
Were all these cases due to Rotavirus? Norwalk agent? Viral gastroenteritis of some other etiology? The authors did not address causality specifically, but assumed that viral illnesses comprised the majority of abrupt vomiting cases among adults presenting to the ED. The major limitation is that children, who are afflicted with frequent "viral gastroenteritis" episodes, were excluded. Other anti-emetics, such as metoclopramide (Reglan), trimethobenzamide (Tigan), and ondansetron (Zofran), do not share the combined effectiveness, availability, tolerability, widespread ED usage, and relatively low cost of the two agents studied in this trial. I am now reconsidering how I treat gastroenteritis with vomiting, and how I teach residents about therapeutic advantages. It seems to me that prochlorperazine wins, hands down.