Pill imprint R 153 has been identified as Ondansetron hydrochloride 4 mg.
Ondansetron (INN) (//; developed and first marketed by GlaxoSmithKline as Zofran) is a serotonin receptor antagonist35-HT used mainly as an antiemetic (to treat nausea and vomiting), often following chemotherapy. It affects both peripheral and central nerves. Ondansetron reduces the activity of the vagus nerve, which deactivates the vomiting center in the medulla oblongata, and also blocks serotonin receptors in the chemoreceptor trigger zone. It has little effect on vomiting caused by motion sickness, and does not have any effect on dopamine receptors or muscarinic receptors.
The 5-HT3 antagonists are a class of drugs that act as receptor antagonists at the receptor35-HT, a subtype of serotonin receptor found in terminals of the vagus nerve and in certain areas of the brain. With the notable exception of alosetron and cilansetron, which are used in the treatment of irritable bowel syndrome, all 5-HT3 antagonists are antiemetics, used in the prevention and treatment of nausea and vomiting. They are particularly effective in controlling the nausea and vomiting produced by cancer chemotherapy and are considered the gold standard for this purpose.
The 5-HT3 antagonists may be identified by the suffix –setron, and are classified under code A04AA of the WHO's Anatomical Therapeutic Chemical Classification System.
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