in general , brain injury can occur due to sudden and severe head strike to a hard object , which can be mild , moderate or severe ( 1 ) .
the main causes of head injury include traffic accidents , falling from heights , physical violence , accidents at work , inside home accidents and during exercise incidents
. however , the most important cause of head trauma in iranian population is traffic accident ( 2 ) . among the warning signs of head trauma are nausea , vomiting , dizziness , headache , blurred vision , and loss of balance , difficulty in sleeping , memory problems , tinnitus and fatigue ( 3 ) .
nausea and vomiting are the most common complications after minor head trauma that in addition to severe harassment of patients increases the risk of aspiration and intracranial pressure rising .
ondansetron is a serotonin 5-ht3 receptor antagonist , which connects to the peripheral and central receptors of serotonin ( 1 ) .
this drug is mostly used in nausea and vomiting after chemotherapy and surgery ( 2 ) .
it does not have any effect on dopamine receptors thus ; it does not have extra pyramidal effect ( 3 ) .
this drug has a half - life of 2 - 7 hours and is metabolized in the liver where it changes into glucuronide and sulfate which is inactive .
its most common side effects include headaches , fatigue , diarrhea , constipation , dizziness and anxiety .
the recommended dose for the treatment of nausea and vomiting is 4 - 8 milligrams ( 4 , 5 ) .
metoclopramide as an old antiemetic is mostly used in high doses , before chemotherapy and for nausea and vomiting caused by various reasons ( 6 - 8 ) .
this drug blocks the dopamine receptors on the peripheral and central dopamine receptors and increases the movement of the upper gastrointestinal tract without increasing secretion ( 9 , 10 ) .
its intravenous absorption takes about 3 minutes and the peak of its effect is about 15 minute .
this drug is metabolized in the liver and its half - life is approximately 4 - 5 hours ( 11 ) .
its most common side effects include dystonia < 10% , fatigue , drowsiness , and flushing .
based on the above - mentioned reasons , the present study was aimed to compare the antiemetic effects of metoclopramide and ondansetron in the treatment of post head trauma nausea and vomiting .

 study design and setting 
  the study was a controlled , randomized , double blind clinical trial , which was conducted in the first 6 months of 2014 in al - zahra and kashani hospitals in isfahan , iran .
the present study was supervised and accepted by the ethics committee of isfahan university of medical sciences .
the study was registered in iranian registry of clinical trial ( irct number : irct2015043012072n6 ) .  
the studied population included patients with minor head trauma associated with nausea and vomiting who were referred to the emergency department .
the patients older than 15 years old , with minor head trauma , nausea and vomiting , and a triage level of 3 or higher based on emergency severity score were included . the exclusion criteria were considered as follow : hemodynamic instability ; pregnancy / lactation ; any neurologic deficit ; restless leg syndrome ; alcohol usage ; consumption of any antiemetic drugs during the 8 hours prior to admission ; previous administration of intravenous fluids ; motion / vertigo related nausea and vomiting ; chemotherapy or radiotherapy ; inability to complete and understand study explanations or outcome measures ; finally allergy or previous adverse reactions to metoclopramide or ondansetron ; and lack of data regarding demographic data and the severity of nausea and vomiting based on the visual analog scale ( vas ) .
the patients were randomly divided into 2 groups : treatment with metoclopramide ( 10mg/2ml , slow injection ) and treatment with ondansetron ( 4mg/2ml , slow injection ) .
for the study to be double blind , the drugs were packed in nameless syringes , and in numbered , dark packs and only the main researcher knew about the drug content .
the patients and the other researchers were blind to the drug content and the treatment group .
drug information and treatment group of the patients would only be revealed if the patients showed extrapyramidal side effects of the drugs , which did not happen in this study .
if the severity of nausea had not decreased at least by 20 mm compared to the rate before the treatment intervention , a rescue dose ( 4 mg ondansetron ) would be prescribed for the patient .
nausea severity was measured using self - rated visual analogue scale ( vas ) before and 20 minutes after the intervention .
vas was a standard 100 mm ( mm ) method on which the left side indicated no nausea and the right side was an indicator of the worst nausea possible . using this scale for assessing nausea severity
was accepted in previous studies . according to these studies the minimum difference in nausea severity counted as clinically significant ,
nausea severity was divided into 3 levels : severe nausea ( vas > 70 mm ) , moderate nausea ( 50 mm < vas < 70 mm ) and mild nausea ( vas < 50 mm ) .
the primary outcome was defined as mean nausea severity according to vas in the twentieth minute post drug administration .
statistical analysis 
  population sample size for each group was determined based on comparing mean nausea severity between the 2 treatment groups .
based on previous studies ( 12 ) , mean and standard deviation of nausea severity reduction before and after ondansetron administration was 40 mm and 24 mm respectively . based on this , by considering  = 0.05 and 90% power (  = 0.1 ) , the sample size of 43 patients in each group was sufficient .
nausea severity was expressed as mean and standard deviation . to compare the 2 groups ,
t - test was used and for comparing the effects of the drug before and after administration , paired t - test was used .
the comparison between the 2 groups was done using the chi square , the fisher exact , or mann - whitney u test .
in all the analyses , p < 0.05 was defined as the level of significance .
finally , 120 patients with minor head trauma were distributed and studied into two groups of 60 patients ( mean age 35.6  14.1 years ; 50.0% male ) .
mean age of metoclopramide and ondansetron treated groups were 36.1  14.0 and 35.0  14.2 years , respectively ( p = 0.69 ) .
the sex distribution in ondansetron ( 45.0% male ) and metoclopramide groups ( 55.0% male ) had no significant difference .
administration of both ondansetron and metoclopramide significantly reduced the severity of nausea ( p < 0.001 ) . the average score of nausea severity before the injection of ondansetron and metoclopramide in the groups were 89.312.5 and 85.3  14.9 , respectively ( p = 0.11 ) .
before intervention 51 patients ( 85.0% ) of the ondansetron group and 47 patients ( 78.3% ) of the metoclopramide group had severe nausea ( vas > 70 mm ) ( p = 0.35 ) .
after intervention only 2 patients ( 3.3% ) of the ondansetron treated and 5 patients ( 8.3% ) of the metoclopramide treated group had severe nausea ( p = 0.16 ) .  
however , changes in the severity of nausea in both groups before and after the treatment revealed that nausea had been decreased significantly in both groups ( p < 0.001 ) ( figure 2 ) .
the incidence of fatigue ( p = 0.44 ) , headache ( p=0.58 ) and dystonia ( p = 0.06 ) had no significant difference in the two groups but the incidence of drowsiness and anxiety in the metoclopramide group was significantly higher ( p < 0.001 ) ( table 1 ) .
2 ( 1.7% ) patients needed the rescue dose which were in the metoclopramide treated group ( p = 0.50 ) .
the present study showed that the antiemetic effect of ondansetron and metoclopramide in patients with minor head trauma is the same .
the frequency of severe nausea in the ondansetron group reduced from 85% to 3.3% while in the metoclopramide group , reduced from 78.3% to 8.3% .
the incidence of drowsiness and anxiety were significantly lower in the ondansetron treated patients .  
the antiemetic effects of ondansetron and metoclopramide have been compared in various studies , the results of which are in line with the current study .
reveals that the effectiveness of ondansetron and metoclopramide compared to the placebo , show no significant difference in decreasing nausea and vomiting in the patients admitted to the emergency department ( 13 ) . also egerton - warburton et al
. expressed in their study that the antiemetic effects of ondansetron and metoclopramide were no different compared to the placebo ( 14 ) .
in addition , barrett et al . and al - ansari et al . have reported similar results ( 12 , 15 ) . in the present study ,
mean pain relief was 48.8 mm in the metoclopramide group and 57.0 mm in the ondansetron ones which was significantly different from the results of the mentioned studies . in this
regard , egerton - warburton et al . showed that administering 4 mg ondansetron and 20 mg metoclopramide resulted in a 27 mm and 28 mm decrease in nausea severity , respectively ( 2 ) .
study was 40 mm for ondansetron and 32 mm for metoclopramide ( 15 ) . concerning the drugs side effects , patanwala et al
. propose in their review study that due to safety , ondansetron is a better choice for the first line of treatment for decreasing nausea and vomiting in the patients admitted to the emergency department ( 16 ) .
the present study also showed that compared to metoclopramide , ondansetron administration , showed less side effects .
6 patients showed side effects in the group treated with metoclopramide , whereas only 2 showed side effects in the group treated with ondansetron ( 14 ) .
if such a group was studied , an assessment of the placebo effect would have been possible .
mean changes of nausea severity before and after intervention in the 2 groups frequency of nausea before and after treatment in both groups
since these complications can have adverse effects on the treatment of patients with brain injury , it is suggested that it may be better to use ondansetron in these patients .
all authors passed four criteria for authorship contribution based on recommendations of the international committee of medical journal editors .
 introduction : nausea and vomiting are the most common complications after minor head trauma that increases the risk of intracranial pressure rising . therefore , the present study was aimed to compare the antiemetic effects of metoclopramide and ondansetron in the treatment of post - traumatic nausea and vomiting . methods : the study was a controlled , randomized , double blind clinical trial , which was conducted in the first 6 months of 2014 in emergency department al - zahra and kashani hospitals in isfahan , iran . the patients with minor head trauma associated with nausea and vomiting were randomly divided into 2 groups : treatment with metoclopramide ( 10mg/2ml , slow injection ) and treatment with ondansetron ( 4mg/2ml , slow injection ) . 
 the comparison between the 2 groups was done regarding antiemetic efficacy and side effects using spss 21 statistical software . 
 results:120 patients with minor head trauma were distributed and studied into two groups of 60 patients ( mean age 35.614.1 years ; 50.0% male ) . 
 administration of both ondansetron and metoclopramide significantly reduced the severity of nausea ( p<0.001 ) . 
 changes in the severity of nausea in both groups before and after the treatment revealed that nausea had been decreased significantly in both groups ( p < 0.001 ) . 
 the incidence of fatigue ( p=0.44 ) , headache ( p=0.58 ) and dystonia ( p=0.06 ) had no significant difference in the two groups but the incidence of drowsiness and anxiety in the metoclopramide group was significantly higher ( p < 0.001 ) . 
 conclusion : the present study indicated that the treatment effectiveness of ondansetron and metoclopramide are similar . 
 however , incidence of drowsiness and anxiety in the metoclopramide was considerably higher . since these complications can have adverse effects on the treatment of patients with brain injury , it is suggested that it may be better to use ondansetron in these patients . 