Ondansetron is a drug used to prevent and treat nausea and vomiting which can be caused by side effects of chemotherapy , radiotherapy or surgery. This medicine should only be taken with a doctor's prescription.

Ondansetron is an antiemetic ( anti- nausea ) which belongs to the group of serotonin receptor antagonists (5HT3 receptors ) . Serotonin itself is a chemical that is naturally produced by the body for various purposes. One of them is to regulate bowel movements and the digestive tract as a whole.

In certain conditions, such as during chemotherapy , radiotherapy , or surgery, the body's serotonin levels will increase. Likewise with the amount of serotonin that binds to the 5HT 3 receptor . This can cause nausea and vomiting effects.

Ondansetron works by blocking the effects of serotonin (5HT3 ) . That way, the effects of nausea and vomiting in the above conditions can be overcome or even prevented.

Ondansetron trademarks: Ceteron, Fudanton, Maxtron, Narfoz, Nausimex, Ondansetron HCl 2H20, Ondansetron HCI Dihydrate, Ondansetron Hydrochloride Dihydrate, Vometron, Zetral

What is Ondansetron?

class Prescription drug
Category Serotonin receptor antagonist antiemetic
Benefit Prevent and treat nausea and vomiting.
Used by Adults and children
Ondansetron for pregnant and lactating women Category B : Animal studies have not demonstrated a risk to the fetus, but there are no controlled studies in pregnant women. It is not known whether ondansetron is absorbed into breast milk. If you are breastfeeding, do not use this medicine before consulting your doctor first.
Drug form Tablets, quick-dissolving tablets, syrups, injections and infusions

Warning Before Using Ondansetron

Note the following points before using this drug:

  • Tell your doctor if you have a history of allergies, especially to ondasetron or other serotonin-blocking drugs, such as granisetron .
  • Tell your doctor if you have liver disease , digestive disorders, severe diarrhea or vomiting, hypokalemia , magnesium deficiency, heart failure, heart rhythm disturbances, especially QT prolongation on the EKG, or bradycardia .
  • Tell your doctor if you have recently had surgery on your stomach or digestive tract.
  • Tell your doctor if anyone in your family has had a cardiac QT prolongation or sudden cardiac arrest.
  • Tell your doctor if you plan or are taking any other medications, including supplements or herbal products.
  • Tell your doctor if you are pregnant, breastfeeding or planning a pregnancy.
  • Do not drive or do activities that require alertness while taking ondansetron, because this drug can cause dizziness and drowsiness.
  • Do not drink alcoholic beverages while undergoing treatment with ondansetron because it can increase the risk of side effects.
  • Immediately see a doctor if an allergic reaction or drug overdose occurs.

Dosage and Rules for Using Ondansetron

The dosage for ondansetron varies, depending on the purpose of the treatment being undertaken, the dosage form of the drug, and the age of the patient. Here is the explanation:

1. Prevent nausea and vomiting due to radiotherapy

Drug form: Oral medicine

adult _

  • Total (whole body) radiotherapy: 8 mg, taken 1–2 hours before radiotherapy.
  • Single high-dose abdominal radiotherapy: 8 mg, taken 1–2 hours before therapy, then every 8 hours for 1–2 days after therapy.
  • Abdominal radiotherapy daily: 8 mg, taken 1–2 hours before radiotherapy, then every 8 hours while radiotherapy is administered.

Drug form: Injection and infusion


  • 8 mg, injected into a vein (intravenous/IV) or muscle (intramuscular/IM) just before radio

Elderly ≥ 75 years

  • 8 mg, IV infusion over 15 minutes, followed by 2 further doses of 8 mg, given 4 hours and 8 hours after the initial dose .

2. Prevent nausea and vomiting due to chemotherapy

Drug form: Oral medicine

Adult patients and children aged > 12 years

  • Chemotherapy with usual emetogenic (nausea-triggering) effects: 8 mg, given 30 minutes to 2 hours before chemotherapy, then 8 mg or 12 hours later.
  • Chemotherapy with severe emetogenic effects: 24 mg as a single dose, given 30 minutes to 2 hours before chemotherapy.
  • Continuation after chemotherapy is finished: 8 mg, twice daily, up to 5 days after chemotherapy.

A child aged 4–11 years

  • Chemotherapy with usual emetogenic effects: 4 mg, given 30 minutes before chemotherapy. The same dose will be given again 4 hours and 8 hours after the initial dose.

Form of drug: Injection or infusion

adult _

  • Chemotherapy with usual emetogenic effects: 8 mg or 0.15 mg/kgBW by slow IV injection.
  • Chemotherapy with severe emetogenic effects: 8 mg IV or IM injection before chemo. The maintenance dose may be given by infusion of 1 mg/hour for 24 hours, or by injection of 8 mg given 4 hours and 8 hours after the initial dose .

Elderly aged < 75 years

  • Maximum dose 16 mg IV infusion over ≥ 15 minutes.

Elderly aged ≥ 75 years

  • Initial dose 8 mg IV infusion over ≥15 minutes. The follow - up dose is 8 mg given 4 hours and 8 hours after the initial dose .

Child ≥6 months

  • 0.15 mg /kg (maximum dose of 8 mg) via IV infusion, given 30 minutes before chemotherapy. Doses can be repeated i again 4 hours and 8 hours after the initial dose.

3. Overcoming nausea and vomiting after surgery

Drug form: Oral medicine


  • 16 mg, given 1 hour before anesthetic administration.

Children with weight ≥40 kg

  • 4 mg, given 1 hour before anesthetic administration. Follow-up dose of 4 mg after 12 hours.

Drug form: Injection

adult _

  • 4 mg, given by IV or IM injection before anaesthetic administration.

Children with weight > 40 kg :

  • 4 mg, given by IV injection prior to administration. Maximum dose is 4 mg per dose.

Children aged ≥1 month and weight≤ 40 kg :

  • 0.1 mg/kgBB, given by IV injection before administration

How to use Ondansetron correctly

Ondansetron injectable and infusion forms will be given by a doctor or medical officer at the doctor's direction.

Be sure to read the instructions on the drug packaging and follow the doctor's recommendations when taking ondansetron in oral form.

Ondansetron drink is available in the form of tablets, fast-dissolving tablets, and syrup. This medicine can be consumed before or after meals, but be sure to follow the doctor's instructions for taking it.

Ondansetron tablets need to be taken with a glass of water. Meanwhile, ondansetron in the form of fast-dissolving tablets is simply placed on the tongue and waited for it to dissolve before being swallowed with saliva.

To consume ondansetron syrup, use the measuring device available in the package. Do not use tablespoons or teaspoons, because the dose can be wrong. Shake the bottle before pouring the medicine into the measuring spoon.

Drinking ondansetron usually needs to be consumed about 1 hour before chemotherapy, radiotherapy, or surgery. Especially after chemotherapy, you may need to continue using this drug for several days afterward, as directed by your doctor.

For patients who forget to take ondansetron, it is recommended to consume it immediately if the gap with the next consumption schedule is not too close. If it is close, skip the dose and do not double the next dose.

Store ondansetron in a dry and cool place away from direct sunlight. Keep this drug out of reach of children.

Ondansetron Interactions with Other Drugs

Interaction effects that can occur if ondansetron are concurrent with certain drugs include:

  • Decreased effectiveness of ondansetron when used with strong CYP3A4 inducers, such as carbamazepine, phenytoin, or rifampicin
  • Decreased pain relief of tramadol
  • Increased effectiveness of ondansetron when used with dexamethasone sodium phoshate
  • Increased risk of developing serotonin syndrome when used with selective serotonin reuptake inhibitors ( SSRIs ), serotonin norepinephrine reuptake inhibitors (SNRIs), MAOIs , mirtazapine, fentanyl , or lithium
  • Increased risk of QT prolongation or arrhythmias when used with atenolol, doxorubicin, daunorubicin, trastuzumab, erythromycin, ketoconazole , or antiarrhythmics, such as amiodarone
  • Increased risk of developing severe hypotension and loss of consciousness when used with apomorphine.

Side Effects and Dangers of Ondansetron

Ondansetron can cause different side effects for each person. Side effects that may occur include:

  • Headache or dizziness
  • Feel like flying
  • Constipation
  • Fatigue and body feeling weak
  • Chills _
  • Drowsiness

Contact your doctor if these side effects do not improve or get worse. Immediately see a doctor if you experience an allergic drug reaction or more serious side effects, such as:

  • Vision becomes blurry or vision is temporarily lost
  • Abdominal pain
  • Muscle cramps or muscle stiffness
  • Chest pain
  • The heart beats slowly, quickly, or irregularly
  • Symptoms of serotonin syndrome , which can be characterized by palpitations, hallucinations, loss of body coordination, feeling very dizzy, fever , feeling restless or anxious, muscle twitching, and severe nausea, vomiting, and diarrhea
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