Etiology		Pathophysiology	Treatment
Metastases
	Cerebral	Increased intracranial pressure, direct chemoreceptor trigger zone effect	Corticosteroids, mannitol, dopamine antagonists, histamine antagonists
	Liver	Toxin buildup	Dopamine antagonists, histamine antagonists
Meningeal irritation		Increased intracranial pressure	Corticosteroids
Movement		Vestibular stimulation (may be worse with morphine)	Acetylcholine antagonists
Mentation (e.g., anxiety)		Cerebral cortex	Anxiolytics (e.g., benzodiazepines, dronabinol [Marinol])
Medications
	Opioids	Chemoreceptor trigger zone, vestibular effect, gastrointestinal tract	Dopamine antagonists, histamine antagonists, acetylcholine antagonists, prokinetic agent, stimulant laxatives
	Chemotherapy	Chemoreceptor trigger zone, gastrointestinal tract	Serotonin antagonists, dopamine antagonists, corticosteroids
	Others (e.g., NSAIDs)*	Chemoreceptor trigger zone	Dopamine antagonists, histamine antagonists
Mucosal irritation
	NSAIDs	Gastrointestinal tract, gastritis	Cytoprotective agents
	Hyperacidity, gastroesophageal reflux	Gastrointestinal tract, gastritis, esophagitis, duodenitis	Antacids
Mechanical obstruction
	Intraluminal	Constipation, obstipation	Manage with laxatives, stool softeners, lubricants, etc.
	Extraluminal	Tumor, fibrotic stricture	Reversible: surgery
			Irreversible: manage fluids, administer corticosteroids, inhibit secretions with octreotide (Sandostatin) or scopolamine (Transderm Scop)
Motility
	Ileus, opioids and other medications	Gastrointestinal tract, central nervous system	Prokinetic agent, stimulant laxatives
Metabolic imbalance
	Hypercalcemia, hyponatremia, hepatic or renal failure	Chemoreceptor trigger zone	Dopamine antagonists, histamine antagonists, corticosteroids; correct electrolyte imbalance
Microbes
	Local irritation (e.g., esophagitis, gastritis caused by infection with Candida species, Helicobacter pylori, herpesvirus, cytomegalovirus)	Gastrointestinal tract	Antibacterials, antivirals, antifungals, antacids
	Systemic sepsis	Chemoreceptor trigger zone	Dopamine antagonists, histamine antagonists, antibacterials, antivirals, antifungals
Myocardial dysfunction
	Ischemia, congestive heart failure	Vagal stimulation, cerebral cortex, chemoreceptor trigger zone	Oxygen, opioids, dopamine antagonists, histamine antagonists, anxiolytics