Ondansetron antiemetic side effects

Ondansetron antiemetic drug is a 5-HT3 receptor antagonist that is prescribed by doctors in patients after surgery, chemotherapy, radiation therapy to reduce symptoms of vomiting and nausea. Ondansetron is on the ETC formulary. Ondansetron has effects on both the central and peripheral systems and on vagus nerve endings or chemoreceptors. In patients receiving chemotherapy, radiation therapy causes the release of serotonin in the small intestine, and through 5-HT receptors to stimulate vagus nerve activation to induce vomiting reflex. At this time, the use of ondansetron helps prevent the release of serotonin, thereby reducing the feeling of nausea, improving the symptoms of vomiting. Ondansetron also reduces the vomiting reflex thanks to its ability to block receptors on the floor of the fourth ventricle.
Ondansetron can be used by both adults and children. Forms of antiemetic ondansetron:
Oral tablet form: with film-coated tablets and lozenges. This form has 2 strengths: ondansetron 4mg and ondansetron 8mg. Oral solution containing ondansetron 4mg/5ml. The current injectable form has 1 strength, ondansetron 8mg/4ml. Clinical and subclinical experimental studies show that the antiemetic drug ondansetron is well absorbed from the gastrointestinal tract. For oral administration, the drug takes effect after about 30 minutes. After entering the body, the drug is mainly metabolized in the liver and then excreted in the form of metabolites in the urine and feces.
The dosage of ondansetron for each patient depends on age, medical condition and severity of symptoms.
For patients undergoing chemotherapy and radiation therapy:
Combination of both injection and oral route. Injectable doses for adults range from 8-32 mg in 1 day, combined with oral 8 mg 12 hours after injection. In children, only 0.15mg/kg body weight injection, 4mg oral dose 12 hours after injection and maximum use in 5 days. For patients after surgery:
Adults appoint 4mg or 16mg intramuscular or intravenous injection 1 hour before surgery. Children over 2 years old should not use more than 4mg intravenously, the dose is 0.1 mg/kg body weight. Do not use more than 8mg/day in patients with cirrhosis, liver failure.

Common side effects:
ADR above 1/100.
For the central nervous system, ondansetron often causes headache, drowsiness, sometimes fever. With the digestive system, the drug causes constipation or diarrhea depending on the location of each patient. Uncommon side effects:
ADRs range from 1/1000 to 1/100. In this range, the drug will cause dizziness, patients often have dry mouth, sometimes have abdominal cramps. One of the less common side effects of ondansetron is the weakening of the musculoskeletal system in users. Rare side effects:
ADR less than 1/1000. The occurrence of rare side effects varies depending on the patient's condition. Side effects may occur on one or more internal organs: Systemic symptoms: anaphylaxis, hypersensitivity to the components of the drug. The drug causes low blood pressure, arrhythmia, tachycardia, headache, even seizures. On the respiratory system, the drug produces bronchospasm, shortness of breath, shallow breathing, wheezing. In addition, the drug also causes chest pain, increased liver enzymes, increased bilirubin in the blood, and purpura.
To limit the occurrence of side effects on people taking ondansetron, when using it, it is necessary to note a few things as follows: Ondansetron should be used for the purpose of prevention instead of treatment. It is recommended that the drug be administered within 24 to 48 hours of chemotherapy.
Pay special attention to the following cases:
Patients with a history of allergy to 5-HT3 receptor antagonists. Patients with a diagnosis of congenital long QT syndrome, or risk factors for QT prolongation, or suspected bowel obstruction. In patients taking drugs known to prolong the QT interval, the combination of ondansetron and ondansetron may cause torsades de pointes. Caution should be exercised in patients with hepatic dysfunction or taking other serotonergic drugs. For pregnant and lactating women: Ondansetron is currently classified as Group B. There is no specific information on whether the drug crosses the placenta or not, but through experimental studies on Ondansetron has been found in animals to be secreted into breast milk. Therefore, in lactating women this drug should not be given. In pregnant women, the use of drugs can be considered, but it is necessary to weigh the benefits and harms when using and must be prescribed by a specialist.
Regarding drug use while driving or operating machinery: Many psychomotor activity tests of the drug have been conducted on these subjects. As a result, the drug does not have much effect on the user's ability to use machines or drive.
When taking an overdose, it is necessary to immediately notify a specialist or go to the nearest medical facility for timely monitoring and treatment, if there are signs of bad health. Note, there is no specific drug to treat these cases specifically.
If you miss a dose, take it as soon as you remember, do not make up for the missed dose.
In summary, ondansetron is a very good antiemetic drug, especially in cancer patients receiving chemotherapy or radiation. However, the drug also has side effects that can affect the patient's health. Side effects that occur in each patient are not the same in both symptoms and severity. Please notify a specialist immediately if you are taking medication and see any unusual health-related symptoms for timely support and treatment, without making the disease worse.
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