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Ondansetron
Last reviewed: 04.07.2025
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Ondansetron is a drug from a subgroup of agents used for tumors of a malignant nature, as well as substances that are used to correct negative signs that arise when administering antitumor drugs.
It has serotonergic and antiemetic activity. The drug blocks the development of the gag reflex, having an antagonistic effect on the endings located in the area of the neurons of the PNS. The substance does not lead to a weakening of the patient's psychomotor activity, and does not cause the development of a sedative effect.
Indications Ondansetron
It is used for nausea, and also to prevent vomiting that develops in connection with radiotherapy or chemotherapy procedures for oncological pathologies.
In addition, it can be prescribed to prevent vomiting and nausea after surgical procedures.
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Release form
The component is released in tablets of 0.004 and 0.008 g - a pack contains 10 such tablets.
In addition, it can be produced in the form of an injection liquid - inside ampoules with a capacity of 2 or 4 ml (1 ml of liquid contains 0.002 g of the active ingredient); in a box - 5 ampoules.
Pharmacodynamics
Ondansetron is a substance that has an antagonistic effect on peripheral (inside the intestine) and central (inside the brain) serotonin (5-HT3) endings.
The drug prevents and eliminates nausea and vomiting that occur due to the release of serotonin during chemotherapy and radiation therapy procedures aimed at eliminating tumors. In case of repeated use, it leads to a slowdown in intestinal peristalsis.
The medication has anti-anxiety activity. It does not affect motor coordination and does not lead to a decrease in performance.
Pharmacokinetics
After an intramuscular injection, blood Cmax values are recorded after 10 minutes, and after oral administration - after 1.5 hours. Eating food prolongs the absorption period without affecting the Cmax values.
Bioavailability values are 60%. The protein synthesis rate is 70-76%; part of the substance passes into erythrocytes. The drug undergoes intensive intrahepatic metabolism.
A small part (5%) is excreted unchanged in urine. The half-life is 3 hours, both when taken orally and when administered parenterally. In elderly people, this figure is 5 hours.
Dosing and administration
In oncology, vomiting with nausea that occurs after therapeutic procedures is called “emetogenic syndrome.”
To prevent the development of this syndrome, 8 mg of the substance should be taken orally 60 minutes before performing antitumor procedures; a similar dose should be taken again 12 hours after therapy.
To prevent late vomiting, which occurs after 24 hours, 8 mg of the drug is taken twice a day for 6 days from the end of antitumor treatment. To achieve a more intense effect, the dose can be increased to 24 mg, also prescribing dexamethasone (12 mg) together with Ondansetron 120 minutes before the chemotherapy procedure.
It is also possible to administer the drug in the form of an injection liquid. In case of moderate intensity of emetogenic syndrome, 8 mg of the drug is used (intramuscularly or intravenously by jet) before each therapeutic procedure. If the syndrome is severe, 8 mg of the drug should be administered intravenously by jet before the chemotherapy session, and then in the same portion and in the same way, at 3-4-hour intervals.
To prevent vomiting with nausea after surgical procedures, 4 mg of Ondansetron is administered intravenously or intramuscularly along with the general anesthesia. In case of vomiting, 4 mg of the substance should be administered 3 times a day.
For children, to prevent postoperative vomiting, 0.1 mg/kg of the drug should be administered intravenously at a low rate after anesthesia.
Children over 2 years of age are given 5 mg/m2 of the drug intravenously before a chemotherapy session; after 12 hours, 4 mg of the drug is prescribed orally. Then the substance is used twice a day in a 4 mg dose for 5 days.
Use Ondansetron during pregnancy
Ondansetron should not be used during pregnancy.
Contraindications
Main contraindications:
- breast-feeding;
- severe intolerance to the medication;
- combined use with apomorphine;
- Long QT syndrome (congenital).
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Side effects Ondansetron
Side effects include:
- temporary increase in liver enzyme levels, diarrhea or constipation and dry mouth;
- convulsions, dystonia, headaches, extrapyramidal manifestations and movement disorders;
- ocular deviation, transient blindness and visual acuity disorder;
- arrhythmia, bradycardia, chest pain, QT prolongation, decreased blood pressure, ventricular tachycardia and ST depression;
- urticaria, Quincke's edema, bronchial spasm, anaphylaxis and laryngospasm;
- hypokalemia and flushing of the face;
- burning sensation in the anal area (when using suppositories), pain in the injection area.
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Interactions with other drugs
The drug should be used with extreme caution together with MAOIs, papaverine, carbamazepine and barbiturates, as well as with erythromycin, griseofulvin, cimetidine and fluoroquinolones. In addition, this list includes rifampicin, metronidazole and diltiazem with lovastatin, macrolides, omeprazole with allopurinol, substances that prolong the QT interval, and ketoconazole.
Combination with tramadol may lead to a decrease in its analgesic activity.
It is forbidden to combine with apomorphine hydrochloride, because it can cause a strong decrease in blood pressure and loss of consciousness.
Attention!
To simplify the perception of information, this instruction for use of the drug "Ondansetron" translated and presented in a special form on the basis of the official instructions for medical use of the drug. Before use read the annotation that came directly to medicines.
Description provided for informational purposes and is not a guide to self-healing. The need for this drug, the purpose of the treatment regimen, methods and dose of the drug is determined solely by the attending physician. Self-medication is dangerous for your health.