Cyclic Vomiting Syndrome (CVS): This condition is characterized by recurrent, severe episodes of vomiting that are separated by periods of normal health. The symptoms presented could align closely with CVS, especially if the patient has a history of similar episodes.
Marijuana-induced intractable vomiting, also known as Cannabinoid Hyperemesis Syndrome (CHS): This condition is directly linked to long-term marijuana use and is characterized by recurrent episodes of severe vomiting. The diagnosis would be highly likely if the patient has a history of chronic marijuana use.

Gastroparesis: A condition where the stomach takes too long to empty its contents, which can lead to nausea and vomiting. It could be considered if the patient has diabetes, has had certain surgeries, or uses certain medications.
Irritable Bowel Syndrome (IBS): Although primarily associated with abdominal pain and changes in bowel movements, some patients with IBS may experience nausea and vomiting, especially if they have a predominant dyspeptic symptom profile.
Functional Dyspepsia: Characterized by recurring signs and symptoms of indigestion that have no obvious cause. Vomiting can be a symptom, especially in severe cases.

Appendicitis: Although vomiting can be a symptom, the key concern would be the presence of abdominal pain, particularly if it migrates to the lower right quadrant. Missing appendicitis could lead to severe consequences, including perforation.
Intestinal Obstruction: Vomiting can be a symptom, especially if the obstruction is high in the gastrointestinal tract. This condition requires immediate medical attention to prevent complications like ischemia and perforation.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause vomiting among other symptoms. While not typically the first symptom, it's crucial to consider IBD due to its potential for severe complications if left untreated.
Gastrointestinal Malignancies: Though less common, certain cancers (like gastric cancer) can present with vomiting. Given the potential severity of missing a cancer diagnosis, it's essential to keep this in the differential, especially in older patients or those with risk factors.

Mitochondrial Neurogastrointestinal Encephalomyopathy (MNGIE): A rare genetic disorder that affects the digestive system and nervous system, causing severe vomiting among other symptoms.
Eosinophilic Gastroenteritis: A rare condition characterized by the presence of eosinophils in the gastrointestinal tract, leading to inflammation and symptoms that can include vomiting.
Chronic Intestinal Pseudo-obstruction: A rare condition where there are symptoms of intestinal obstruction without any physical blockage. Vomiting can be a significant symptom, especially during episodes of pseudo-obstruction.