Download EMETICS AND ANTI-EMETICS Nausea is an unpleasant feeling in

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- prochlorperazine, Compazine and Phenergan

5-HT3 antagonists-Zofran, ondansetron, palonosetron, granisetron and dolasetron

Dopamine receptor antagonists-Reglan

Antihistamines- Antivert, Benadryl, Dramamine

Anticholinergics-Scopolamine

Other agents that may be used for chronic nausea and vomiting, benzodiazepines and
tri-cyclic antidepressants.
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.