Zofran (ondansetron) is an antiemetic that doctors often prescribe to prevent nausea and vomiting caused by chemotherapy, radiotherapy, and surgery, and sometimes for other severe vomiting after the doctor's assessment [3]. It is used in children, pregnant women, and adults only under medical supervision. Common side effects include headache and constipation, and it requires caution in patients with heart rhythm disorders.
What Is Zofran and Why Do Doctors Prescribe It?
Zofran (Zofran) is the brand name of ondansetron, and it is available in our drug directory as tablets at 4 mg and 8 mg strengths. You can review its general information on the Zofran page in the Clinics Jo drug directory.
Ondansetron belongs to a group of medicines called 5-HT3 serotonin receptor antagonists. It works by blocking the effect of serotonin, a natural substance in the body that can trigger nausea and vomiting [3].
This medicine relieves the symptom but does not treat the cause. Nausea and vomiting can result from many causes, including gastritis and enteritis, food poisoning, migraine, reflux, bowel obstruction, and some medications [2]. Therefore, Zofran does not replace diagnosis, and persistent vomiting of unknown cause needs a doctor. To learn about the symptom itself, you can read the Vomiting entry in the medical glossary.
When Is Zofran Used: Chemotherapy, After Surgery, and Gastroenteritis
The most common use of Zofran is preventing nausea and vomiting caused by chemotherapy and radiotherapy, as well as nausea and vomiting after surgery [3]. The following table summarizes the most important situations.
| Situation | Role of Zofran | Notes |
|---|---|---|
| Chemotherapy and radiotherapy | Prevention of nausea and vomiting | The first dose is usually given before treatment starts, and later doses depend on the type of treatment [3] |
| Surgical operations | Prevention of nausea and vomiting | It may be given before surgery and may also be given afterward [1] |
| Severe persistent vomiting | Assessed by the doctor after identifying the cause | Not used as a substitute for diagnosis |
| Pregnancy | Sometimes used to prevent and treat vomiting | A medical decision after weighing benefits and risks [3] |
If you are receiving chemotherapy, see Chemotherapy-Related Nausea and Vomiting for a more complete understanding of this condition.
What About Gastroenteritis?
Vomiting in viral gastroenteritis usually stops within a day or two, and in most cases home treatment based on fluids is sufficient [4]. Therefore, not every patient who vomits needs an antiemetic. Only the doctor decides whether your condition requires medication and when.
How Is Zofran Taken? Forms, Dosage, and Missed Doses
Ondansetron is available as regular tablets, orally disintegrating tablets, and oral solution [3]. It is also given as an injection into a vein or muscle, administered by medical staff in a hospital or clinic [1].
The usual adult dose specified by the doctor or pharmacist, as listed in our drug directory, is 4–8 mg every 8 hours. This is a reference figure and not a prescription for you, as the doctor adjusts it according to your condition, the cause of vomiting, and liver function. Do not increase the dose or shorten the interval between doses, as the medical source confirms that the medicine should be taken exactly as prescribed [3].
- Orally disintegrating tablet: Remove it from the pack immediately before taking it, using dry hands, and do not push it through the foil. Place it on your tongue, where it dissolves within seconds, and swallow it with saliva [3].
- Missed dose: Take it as soon as you remember, unless the next dose is close, in which case skip the missed one. Do not double the dose to make up for it [3].
- Phenylketonuria (PKU): Orally disintegrating tablets contain aspartame, which converts to phenylalanine, so tell your doctor if you have this condition [3].
- Storage: Keep the medicine in its sealed pack, away from children [3].
Unless your doctor tells you otherwise, continue your usual diet while taking the medicine [3].
Is Zofran Suitable for Children?
A doctor may prescribe Zofran for some children, but the decision is purely medical. Our drug directory states that 6 months is the minimum age in the available information, but this does not mean that every child who vomits needs the medicine. A child's dose is always based on weight and prescribed by a doctor or determined by the pharmacist's guidance, and it is not appropriate to estimate the dose from adult tablets.
In most episodes of vomiting in children, the main priority remains preventing dehydration. The UK National Health Service (NHS) advises giving plenty of fluids in small sips if the child is vomiting, continuing breastfeeding or bottle feeding with smaller, more frequent feeds, and not diluting infant formula [4].
- Do not give children under 12 years old a medicine to stop diarrhea [4].
- Do not give aspirin to anyone under 16 years old [4]. For details, read Reye Syndrome and the Risk of Aspirin in Viral Infections in Children.
- Do not use a medicine prescribed for another family member; see Can I use a prescription medicine prescribed for another member of my family?
For practical details on dehydration in young children, read Diarrhea and Vomiting in Children: Treatment and Prevention of Dehydration and the Pediatric Gastroenteritis page. Health centers and mother and child care centers run by the Ministry of Health are available in the governorates, and you can visit them to have your child assessed.
Is Zofran Suitable During Pregnancy?
Nausea and vomiting are among the most common symptoms of pregnancy, known as morning sickness [2]. Ondansetron is sometimes used to prevent and treat vomiting during pregnancy [3]. However, "sometimes" means it is an individual medical decision and not a first-line solution for every pregnant woman.
According to our drug directory, its use in pregnancy is left to the specialist's judgment in severe cases, especially when the first-line options have not worked. The directory classifies it as Pregnancy Category B, but this classification does not mean it is free of any risk. Medical sources advise informing the doctor if you are pregnant, planning a pregnancy, or breastfeeding, and contacting the doctor if you become pregnant while using the medicine [1].
Before considering any medication, MedlinePlus recommends simple steps, including eating plain crackers before getting up in the morning, eating smaller, more frequent meals, and avoiding strong smells [2]. You can find broader information in the Nutrition for Pregnant and Breastfeeding Women service.
Seek your doctor's advice early if you cannot keep fluids down, or if signs of dehydration appear, as described in the warnings section below.
What Are Zofran's Side Effects?
Zofran is generally well tolerated. Its most common side effects are headache and constipation, followed by weakness, fatigue, drowsiness, and chills [3]. According to our drug directory, a temporary flushing of the face may also occur.
Constipation During Treatment
Constipation is bothersome, especially for those taking the medicine in repeated courses. Increasing fluids and fiber usually helps, and the doctor or pharmacist may recommend a gentle laxative if needed. For children, see Constipation in Children before giving any treatment.
Symptoms That Require Immediate Contact
Contact your doctor immediately or call for emergency help if any of the following symptoms appear [3]:
- A skin rash, itching, or hives, or swelling of the eyes, face, lips, tongue, or throat, hoarseness, or difficulty breathing or swallowing. For more on allergies, see Drug Allergy.
- Chest pain, shortness of breath, dizziness, fainting, or a rapid, slow, or irregular pulse.
- Blurred vision or loss of vision.
- Agitation, hallucinations, severe sweating, fever, loss of balance, muscle spasms, convulsions, or confusion, which are signs that may be associated with serotonin syndrome.
Symptoms of overdose include sudden temporary loss of vision, dizziness, fainting, constipation, and irregular pulse [3]. If the affected person collapses, has a seizure, or cannot be woken, call 911 immediately.
Who Needs Special Caution and What Are the Drug Interactions?
Tell your doctor or pharmacist before starting if you or a family member has long QT syndrome, a rare heart problem that can cause irregular heartbeat and fainting. Also tell them about any other heart rhythm disorder, low potassium or magnesium in the blood, heart failure, or liver disease [3]. The same warnings apply to the intravenous form [1].
According to our drug directory, ondansetron may prolong the QT interval, especially with high intravenous doses or in the presence of predisposing factors. In severe liver failure, there is a daily dose ceiling set by the doctor. Any palpitations or fainting during use require medical review.
| Type | Examples | Why It Matters |
|---|---|---|
| Contraindicated medicine | Apomorphine | Risk of severe drop in blood pressure |
| Medicines that prolong QT | Some antiarrhythmic drugs, antipsychotics, and some antibiotics | Increase cardiac caution |
| Painkiller | Tramadol | May reduce its pain-relieving effect |
| Enzyme inducers | Rifampicin, carbamazepine | Lower ondansetron levels in the blood |
| Other serotonergic medicines | Some antidepressants | Theoretical concern for serotonin syndrome |
Write a list of all your medicines, both prescribed and non-prescribed, along with vitamins and supplements, and bring it with you to every medical visit [3]. Do not start, stop, or change any medicine during treatment without consulting your doctor or pharmacist [1]. See also What should I do if I am taking medication and considering using an herb?
What Should I Do at Home While Vomiting?
Whether or not you have been prescribed medicine, home measures remain essential [2]:
- Drink enough fluids. If you cannot tolerate drinking a lot, take small amounts of clear fluids at frequent intervals.
- Eat light foods, and avoid spicy, fatty, and salty foods.
- Eat smaller, more frequent meals, and avoid strong smells.
The UK guidance adds avoiding fruit juice and fizzy drinks, as they may worsen diarrhea [4]. You can find more details in Foods to Avoid When You Have Nausea and Vomiting. Infections spread easily, so wash your hands with soap and water, and stay at home until at least two days have passed without vomiting or diarrhea [4].
When Should You See a Doctor or Go to the Emergency Room?
MedlinePlus advises contacting a healthcare provider immediately if poisoning is suspected, if vomiting lasts more than 24 hours, if there is blood in the vomit, severe abdominal pain, severe headache with stiff neck, or signs of dehydration [2]. For details, see What should I do if vomiting lasts more than 24 hours? and the article Nausea and Vomiting: Causes and Warning Signs.
Signs of Dehydration
- Dry mouth, reduced urination, and dark urine [2].
- In infants and children under 5 years old: fewer wet diapers [4].
See a Doctor or Consultant Today If:
- You are worried about an infant under 12 months old, or the child has stopped feeding during the illness [4].
- Signs of dehydration persist despite oral rehydration solutions, or you cannot keep fluids down [4].
- There is bloody diarrhea, diarrhea lasting more than 7 days, or vomiting lasting more than two days [4].
Call 911 or Go to the Nearest Emergency Room If:
- You vomit blood or material that looks like coffee grounds, or the vomit is green [4].
- You suspect swallowing a toxic substance. Do not try to force the person to vomit, as explained in Should I try to make a poisoned person vomit?
- Neck stiffness with pain when looking at light, sudden severe headache, or sudden severe abdominal pain appears [4].
- Bluish or pale skin, lips, or tongue appears, or there is severe difficulty breathing, or confusion and an unusual lack of response [4].
How Do I Find the Right Doctor or Clinic in Jordan?
The appropriate specialty depends on the cause. Vomiting related to chemotherapy is usually followed up by an oncologist, vomiting in young children is assessed by a pediatrician, and pregnancy is followed by an obstetrician-gynecologist. For recurrent vomiting in adults, the assessment often begins with an internist, a family medicine physician, or a gastroenterologist.
On Clinics Jo, you can search by specialty and governorate, read a doctor's or clinic's profile, and contact or book where the profile allows. You can also browse the Doctors Directory for Chemo Nausea and Vomiting Assessment in Jordan or the Clinics Directory for Chemo Nausea and Vomiting Assessment. These directories are informational lists only and do not represent a medical quality ranking.
- Make sure the doctor's specialty in their profile suits your condition.
- Check the clinic's location and the contact or booking options available.
- Read the services listed in the profile before your appointment.
Useful Questions for Your Doctor
- What is causing my vomiting, and do I need tests such as blood or urine tests?
- Do I really need Zofran, and for how long?
- Does it interact with my other medicines, or with a problem in my heart or liver?
- What signs should prompt me to return to you or go to the emergency room?
Buy medicines from licensed pharmacies, as medicines and their general prices in Jordan are regulated by the Jordan Food and Drug Administration (JFDA), and ask the pharmacist about any questions regarding the dose or packaging. Remember that this article is for education and does not replace consulting a doctor.
Frequently asked questions
Is Zofran safe for children?
A doctor may prescribe it for some children, and the drug directory lists 6 months as the minimum age. A child's dose is based on weight and prescribed by a doctor or determined by the pharmacist's guidance, and it must not be given from adult tablets. In most episodes of vomiting, the main priority is small, frequent amounts of fluids and monitoring for signs of dehydration.
Can a pregnant woman use Zofran?
Ondansetron is sometimes used for pregnancy-related vomiting, but the decision rests with the doctor after weighing benefits and risks, especially in severe cases where first-line options have not worked. Tell your doctor if you are pregnant or planning a pregnancy, and do not start or stop the medicine on your own.
What are the most common side effects of Zofran?
The most common are headache and constipation, and tiredness, weakness, drowsiness, or chills may also occur. Hives with facial swelling, shortness of breath, dizziness and fainting, or irregular pulse require contacting a doctor immediately or going to the emergency room.
Does Zofran cause constipation, and how can I relieve it?
Yes, constipation is one of its common symptoms, especially with repeated courses. Drinking fluids and increasing fiber usually helps, and the doctor or pharmacist may recommend a gentle laxative if needed. If constipation lasts or is accompanied by severe abdominal pain, see your doctor.
Who should be careful when using Zofran?
People with long QT syndrome, heart rhythm disorders, or heart failure, those with low potassium or magnesium, and those with liver disease. It is also contraindicated with apomorphine, and caution is needed with medicines that prolong QT and with tramadol. Tell your doctor about all your medicines before starting.
When does vomiting become an emergency?
When there is bloody vomit or vomit that looks like coffee grounds, suspected poisoning, sudden severe headache, neck stiffness, sudden severe abdominal pain, confusion, difficulty breathing, or bluish skin. Call 911 or go to the nearest emergency room immediately.
Sources and references
- Ondansetron Injection: MedlinePlus Drug Information — MedlinePlus — U.S. National Library of Medicine. Accessed: 2026-10-26.
- Nausea | Vomiting — MedlinePlus — U.S. National Library of Medicine. Accessed: 2026-10-26.
- Ondansetron: MedlinePlus Drug Information — MedlinePlus — U.S. National Library of Medicine. Accessed: 2026-10-26.
- Diarrhoea and vomiting — NHS (UK National Health Service). Accessed: 2026-10-26.
