The expulsion of the STOMACH contents through the mouth. When the effort of vomiting is made, but nothing is brought up, the process is known as retching. When vomiting occurs, the chief effort is made by the muscles of the abdominal wall and by the diaphragm contracting together and squeezing the stomach. The contraction of the stomach wall is also a factor, and an important step in the act consists of the opening, at the right moment, of the cardiac or upper orifice of the stomach. This concerted action of various muscles is brought about by a vomiting centre situated on the floor of the fourth ventricle in the BRAIN.
Vomiting is brought about by stimulation of this nervous centre, in most cases provoked by sensations coming from the stomach itself. Emotional distress may cause vomiting, as may acute anxiety and unpleasant experiences such as seeing an accident, suffering severe pain or travel sickness. Of the drugs which cause vomiting, some act only after being absorbed into the blood and carried to the brain, although most are irritants to the mucous membrane of the stomach (see EMETICS); various diseases of the stomach, such as cancer, ulcer and food poisoning act in a similar way. Stimulation – not only of the nerves of the stomach, but also of those supplying other abdominal organs – produces vomiting; thus in obstruction of the bowels, peritonitis, gall-stone colic, renal colic, and even in some women during pregnancy, vomiting is a prominent symptom.
Direct disturbance of the brain itself is a cause: for example, a blow on the head, a cerebral tumour, a cerebral abscess, meningitis. Nausea and vomiting are common symptoms that may arise from local disease of the gastrointestinal tract, but they are also associated with systemic illness – for example, DIABETES MELLITUS or kidney failure (see KIDNEYS, DISEASES OF) – and also with disturbances of labyrinthine function, such as motion sickness and acute labyrinthitis.
Treatment should be of the underlying cause, once it is determined. Simply using a drug to treat the symptom can hinder accurate diagnosis. If antiemetic drug treatment is indicated, the choice of drug depends on the cause of the vomiting.
Granisetron and ondansetron are 5-hydroxytryptamine (5HT3) antagonists often used in treating nausea and vomiting induced by CHEMOTHERAPY or RADIOTHERAPY and in prevention and treatment of post-operative nausea and vomiting. The cannabinoid Nabilone is also used for the former reason. Prochlorperazine may be prescribed for severe nausea, vomiting, VERTIGO and disorders of the LABYRINTH of the EAR.
Vomiting may occur after surgical operations and this is due to the combined effects of analgesics, anaesthetic agents and the psychological stress of operation. Various drugs can be used to prevent or stop post-operative vomiting.
Nausea and vomiting are common symptoms in pregnancy. Drugs are best avoided in this situation as they may damage the developing FETUS. Simple measures, such as the taking of food before getting up in the morning and reassurance, are often all that is necessary.