A Randomized, Facorial Design Study to Optimize the Dose of Parenteral Metoclopramide

The most effective dose of metoclopramide for treatment of nausea in the emergency department setting has not been thoroughly investigated. One pilot study among emergency department patients in Australia found no statistical difference between 10 mg and 0.4 milligrams/kilogram; another investigation suggests that the anti-emetic effect of 10 milligrams of metoclopramide is no more effective than placebo. In contrast, investigations focusing on chemotherapy patients and post-operative patients suggest that higher dosage metoclopramide is more effective in treating nausea and vomiting. This emergency department study will compare the anti-emetic efficacy of 10 milligrams and 20 milligrams of metoclopramide by using the visual analog scale.

In addition to evaluation of dose, we will evaluate one of the most common side affects of metoclopramide, akathisia. Akathisia is characterized by a subjective component of restlessness and an objective component in the form of the inability to remain motionless. Anti-cholinergic medications are known to reduce extrapyramidal symptoms such as akathisia when dopamine function is impaired in the basal ganglia. In fact, the use of diphenhydramine has been shown to reduce the incidence of akathisia in patients receiving a different anti-emetic, prochlorperazine. However, no research has focused on the use of anti-cholinergic medications to reduce metoclopramide induced akathisia. This investigation will assess the use of 25 mg of diphenhydramine in preventing metoclopramide induced akathisia in ED patients being treated for nausea/vomiting.