Nausea and Vomiting:
Nausea and vomiting are commonly associated symptoms with many diseases. Nausea is a subjective sensation whereas vomiting is the reflexive action of the expulsion of gastric contents. It is important to differentiate vomiting from regurgitation, rumination and bulimic.
In the community, nausea (with or without vomiting) is most likely to be associated with infection, particularly gastrointestinal infection. Vestibular disorders can also cause vomiting as can motion sickness. Nausea and vomiting can also result from pain, for example, migraine and severe cardiac pain. Many medications have known to cause nausea and occasionally vomiting as a common dose-related (Type A) adverse effect. This is particularly common with opioid use in palliative care. Nausea and vomiting also occur post-operatively or in association with therapies which include cytotoxic chemotherapy, or radiotherapy.
Causes of Nausea and Vomiting
I. An intracranial Migraine Raised intracranial pressure (a tumour, infection, haemorrhage, hydrocephalus, etc.)
ii. Labyrinthine Iatrogenic Labyrinthitis, motion sickness, Ménière’s disease, otitis media Cancer chemotherapy Many other medicines (e.g. opioids) Radiotherapy Postoperative
Endocrine/ metabolic Pregnancy, uraemia, diabetic ketoacidosis, hyperthyroidism, hyperparathyroidism, hypoparathyroidism, Addison’s disease, acute intermittent porphyria
Infectious Gastroenteritis (viral or bacterial) Other infections elsewhere
Gastrointestinal disorders Mechanical obstruction (gastric outlet or small bowel) Organic gastrointestinal disorders (e.g. cholecystitis, pancreatitis, hepatitis, etc.) Functional gastrointestinal disorders (e.g. non-ulcer dyspepsia, irritable bowel syndrome, etc.)
Psychogenic disorders Psychogenic vomiting, anxiety, depression
Pain related Myocardial infarction
Managing the patients with nausea and vomiting requires three steps.
1. Look for any complications and correct if any are present. This includes correction of dehydration, hypokalaemia and metabolic alkalosis in the acute situation with symptoms of less than 4 weeks duration. They is a gradual weight loss and malnutrition during chronic episodes of nausea/vomiting, that is, when symptoms have been present for 4 weeks or longer.
2. Possibly, identify the underlying cause and initiate appropriate treatment. Here it is important to be aware of endocrine conditions such as hypercalcaemia, hyponatraemia and hyperthyroidism can result in vomiting.
3. Implement therapeutic strategies to suppress or eliminate symptoms (these depend on the severity and clinical context). Mostly, antiemetics are prescribed only when the cause of the nausea and/or vomiting is known, since by suppressing symptoms, they may otherwise delay diagnosis of any underlying disease. This is especially true in children. However, they may sometimes be necessary temporarily in situations when directly addressing the underlying cause will not bring relief of symptom sufficiently.
Drug Therapy in the Treatment Of Nausea & Vomiting
They are wide range of antiemetic drugs available in the market that help in antagonising the neurotransmitter receptors involved in the pathophysiology of nausea and vomiting. These classes of drugs are generally distinguished from each other by the identity of their main target receptor, although some act at more than one receptor.
Antihistamines This group of medicines includes cinnarizine, cyclizine, diphenhydramine, dimenhydrinate and promethazine. They have some efficacy in nausea and vomiting caused by a wide range of conditions, including motion sickness and postoperative nausea and vomiting (PONV).
Anticholinergics This class one of the oldest antiemetics, of which many members are potent inhibitors of muscarinic receptor (M1 ) activity both peripherally and centrally. Many anticholinergic drugs like atropine, hyoscine and glycopyrronium have been used preoperatively to inhibit salivation and excessive respiratory secretions during anaesthesia.
Phenothiazines and butyrophenones: Phenothiazines (e.g. prochlorperazine, perphenazine, and trifluoperazine) and butyrophenones (e.g. haloperidol and droperidol) act as antagonists at dopamine (D2) receptors in the CTZ, but may also have cholinergic (M1 ) and histaminergic (H1 ) receptor antagonist activity.
Metoclopramide At lower doses, metoclopramide acts as a selective D2 antagonist at the CTZ and its effects mirror those of the phenothiazines and butyrophenones.
Domperidone Although domperidone does not readily cross the BBB, it is a selective antagonist of D2 receptors at the CTZ, which lies outside the BBB in the area postrema. It may also have peripheral effects that result in increased
gastrointestinal motility and faster gastric emptying.
Corticosteroids are known to have antiemetic effects. Their mechanism of action is unclear but steroid receptors are thought to exist in the area postrema. As single agents, they appear to be at least as effective as prochlorperazine in preventing nausea and vomiting associated with mild to moderately emetogenic cytotoxic chemotherapy.
Nausea and vomiting are symptoms caused by a variety of underlying causes. Thorough clinical assessment and appropriate investigations should be undertaken when prescribing a therapeutic trial of an antiemetic. The choice of agent(s) should be based upon the likely cause and severity of the symptoms, the possible underlying pathophysiology, and the recommendations of evidence-based guidelines which take into account clinical effectiveness and cost-effectiveness.