Emetics: Substance that produces vomiting.
Anti-emetics: A drug that is effective against vomiting and nausea.
Emetics and Anti-emetics
Nausea is an unpleasant feeling in the back of throat and stomach that may lead to vomiting.
Symptoms of nausea: Dizziness, light-headedness, trouble swallowing, skin temperature changes, and a fast heart rate.
Pathophysiology: Three primary Pathophysiological pathways are involved in the stimulation of the physiologic vomiting center in the medulla that directly mediates nausea and vomiting. This center can be stimulated by vestibular fibers, afferent visceral fibers, and input from the chemoreceptor trigger zone in the base of the fourth ventricle. The neurotransmitters acetylcholine, dopamine, histamine, and serotonin frequently are implicated in these pathways and are the targets of most therapeutic modalities.
Causes of nausea and vomiting: Food poisoning, Pregnancy, pneumonia, bladder and kidney infections, meningitis Motion sickness and ear infections.
Anti-emetics: Anti-emetic drugs works by interfering or blocking or binding with the receptors in the brain and stomach that trigger nausea and vomiting.
Treatment for nausea and vomiting: The treatment of nausea and vomiting may depend on the cause. However, the following general measures are appropriate for any patient with significant nausea and vomiting.
A.Correction of Fluid and Electrolyte Imbalance: Loss of body fluids results in dehydration and alteration in levels of minerals in the blood. Fluid replacement is usually performed with intravenous saline solution containing potassium. Potassium and sometimes magnesium levels may be low in the blood and may need to be added to the intravenous fluid.
B.Nutritional Support: Initially, patients should not eat solid food or may need to stop consuming food and drink. When feeding resumes, clear liquids are given first and diet advances as tolerated.
C.Therapy for Symptom Relief: Medications for nausea and vomiting may be given to prevent symptoms or to suppress symptoms (e.g., before chemotherapy or immediately after surgery) after they have begun.
Phenothiazines: The first group of drugs that has shown to be effective antiemetic activity, phenothiazines, such as prochlorperazine, this drug acts by blocking the dopamine receptors. It is effective against low or moderately emetogenic agents. Although increasing the dose improves antiemetic activity.
Adverse effects: Extra pyramidal symptoms, hypotension, sedation and restlessness.
5-HT3 receptor antagonists: The specific antagonists of the 5-HT3 receptor are ondansetron; palonosetron, granisetron, and dolasetron selectively block 5-HT3 receptors in the periphery (visceral vagal afferent fibers) and in the brain (chemoreceptor trigger zone). Adverse effects: Headache, electrocardiographic changes.
Benzamides: One of several substituted benzamides with antiemetic activity is metoclopramide; at high doses it is highly effective against the highly emetogenic cisplatin, preventing emesis in 30-40% of patients and reducing emesis in the majority.
Adverse effects: Diarrhea, sedation, and extra-pyramidal symptoms.
Butyrophenones: The butyrophenones are moderately effective antiemetic. Droperidol and haloperidol act by blocking dopamine receptors. Droperidol had been used most often for sedation in endoscopy and surgery, usually in combination with opiates or benzodiazepines. Benzodiazepines: The antiemetic potency of alprazolam and lorazepam is low. Their beneficial effects may be due to their anxiolytic, sedative and amnesic properties.
Neurokinin-1 receptor blocker: Aprepitant belongs to a new family of antiemetic agents. It targets the neurokinin receptor in the brain and blocks the actions of the natural substance. It is usually administered orally with Dexamethasone and palonosetron. It undergoes extensive metabolism, primarily by CYP3A4.
Adverse effects: Constipation and fatigue.
Combination regimens: Antihistamines, such as diphenhydramine, are often administered in combination with high-dose metoclopramide to reduce extra-pyramidal reactions or with corticosteroids to counter metoclopramide-induced diarrhea.
Antiemetic drugs are often combined to increase antiemetic activity or decrease toxicity. Corticosteroids, most commonly Dexamethasone, increase antiemetic activity when given with high-dose metoclopramide, a 5-HT3 antagonist, butyrophenone, phenothiazine, a cannabinoid, or a benzodiazepine.
Emetics, ctz center, vomiting, nausea
