Our current research includes a comparative study between three types of drugs whose abuse causes vomiting, these drugs are (prochlorperazine, metoclopramide, and ondansetron). The effectiveness evaluation of these drugs observed in patients with postcontusion vomiting, this study performed in Imam Al-Hussein medical city and Imam Al-Huja hospital through the period between June of 2015 and March of 2022. It has been shown through our comparative study that the cases of vomiting that occurred are due to the harmful stimulation of the vomiting center with direct or indirect irritation of the gastrointestinal tract, the vestibular system, the chemo-receptor trigger position, and higher centers in cortex and thalamus. Each type of these drugs had a negative effect because of its interaction with the other drug, leading to the some processes characterized by enhanced the releasing of acetylcholine, causes the increasing of lower esophageal sphincter LES and gastric tone, accelerates the gastric emptying, and transit via the gut.