Dolasetron: what it treats, how to take it, side effects
Last updated September 6, 2026.
**Dolasetron is a prescription anti-nausea medicine in the 5-HT3 receptor antagonist class, sold under the brand name Anzemet.** Chemotherapy and surgery release serotonin in the gut and the brain's vomiting center, and dolasetron blocks the 5-HT3 receptors that carry that signal, so the urge to vomit never fully starts. It works best when taken before the trigger rather than after nausea is already severe. The most important safety point is that dolasetron can slow the electrical recovery of the heart (QT prolongation), so the intravenous form must never be used to prevent chemotherapy-induced nausea, and anyone with a heart rhythm problem or low potassium or magnesium needs that corrected and checked first.
What does it treat?
Dolasetron tablets are used to prevent nausea and vomiting caused by moderately emetogenic chemotherapy, the kind of drug-triggered sickness that builds over the hours after an infusion rather than a passing queasy moment. The tablets are also used to prevent nausea and vomiting after surgery and anesthesia, and the injection given in a clinical setting is used both to prevent and to treat post-operative nausea and vomiting once it appears. It is not a treatment for motion sickness, morning sickness, food poisoning, stomach flu, or everyday indigestion, and it does not settle heartburn or reflux. Dolasetron is sold as a single ingredient product, so there are no common combination pills; clinicians often pair it with dexamethasone or an NK1 blocker like aprepitant when the chemotherapy regimen is more likely to cause vomiting.
How do you take it?
Dolasetron comes as 50 mg and 100 mg tablets and as an injection given by a nurse or anesthesia team. For chemotherapy, the usual adult dose is one 100 mg tablet by mouth within one hour before the infusion starts; for preventing nausea after surgery, it is one 100 mg tablet by mouth within two hours before the procedure. Children 2 to 16 years old are dosed by weight, 1.8 mg/kg before chemotherapy and 1.2 mg/kg before surgery, up to a 100 mg maximum in either case. The injection for post-operative nausea is 12.5 mg as a single adult dose, and the intravenous form is not used at all for preventing chemotherapy nausea. The practical ceiling is 100 mg by mouth in a day, taken as one dose, and you should not repeat it or add extra tablets if you still feel sick. You can take it with or without food, with a full glass of water. Because it is a single pre-treatment dose rather than a daily pill, there is no standard missed-dose rule: if you forget it before chemotherapy or surgery, tell the treatment team when you arrive instead of doubling up. Stop and call a doctor if you feel your heart pounding, racing, or skipping, if you feel faint or lightheaded when standing, or if vomiting continues to the point where you cannot keep fluids down.
Side effects to know
- Common: Most people take one dose and notice little, but headache, dizziness, tiredness, and either diarrhea or constipation are the effects reported most often, and they usually fade within a day.
- Serious: Get help right away for a fast, slow, or irregular heartbeat, chest pounding, fainting, or near-fainting, since dolasetron can prolong the QT interval and, rarely, trigger torsades de pointes or complete heart block. Also stop the drug and seek care for signs of serotonin syndrome (agitation, confusion, hallucinations, fever, sweating, muscle twitching or stiffness, fast heartbeat) or for an allergic reaction with hives, swelling of the face, lips, or tongue, or trouble breathing.
Who should not take it?
Do not take dolasetron if you have ever had an allergic reaction to it or to another 5-HT3 blocker such as ondansetron or granisetron. Talk to a doctor first if you have congenital long QT syndrome, any heart block or slow heart rate, heart failure, a recent heart attack, or if you have low potassium or low magnesium from vomiting, diarrhea, or diuretics, because those levels should be corrected before dosing. The same conversation matters if you take antiarrhythmic drugs, high-dose diuretics, methadone, certain antibiotics or antipsychotics that affect heart rhythm, or if you have had a high cumulative dose of an anthracycline chemotherapy drug. Levels of the active form rise with cimetidine and drop with rifampin, and atenolol slows its clearance, so your team may adjust monitoring. Because dolasetron acts on serotonin, tell your clinician about SSRIs, SNRIs, tricyclics, triptans, MAO inhibitors, linezolid, lithium, tramadol, fentanyl, or St. John's wort. The FDA labeling reports no adequate data on dolasetron use in pregnancy and no data on whether it passes into breast milk, so tell your clinician if you are pregnant, planning pregnancy, or nursing and decide together. There is no direct interaction with alcohol, but alcohol adds to dizziness and drowsiness and irritates an already unsettled stomach, so skip it around the time you take a dose.
When is it an emergency?
Call 911 for fainting or collapse, a seizure, chest pain, trouble breathing, or swelling of the face, lips, or tongue after a dose. For a suspected overdose, or if a child swallows dolasetron tablets, call Poison Control at 1-800-222-1222 right away; too much can cause severe dizziness, a sharp drop in blood pressure, and dangerous changes in heart rhythm, and someone who has taken extra needs heart monitoring rather than watchful waiting at home. Also get same-day care if your heart is racing or skipping beats, if you feel lightheaded every time you stand, or if you develop fever with agitation, muscle stiffness, and twitching while on a serotonin medicine. Vomiting that will not stop, with no urine for 8 hours or more, dry mouth, and confusion, means dehydration that needs treatment in person.
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Common questions
What is the maximum dose of dolasetron I can take?
For adults the oral dose is 100 mg, taken once as a single dose before chemotherapy or before surgery. That single dose is also the daily ceiling, so you should not take a second tablet later in the day if you still feel sick. Children 2 to 16 years old are dosed by weight, 1.8 mg/kg before chemotherapy or 1.2 mg/kg before surgery, and never above 100 mg. Higher doses raise the risk of heart rhythm changes without reliably controlling nausea better. If one dose is not holding you, call your treatment team, because they will usually add a different class of anti-nausea drug rather than more dolasetron.
Can I drink alcohol while taking dolasetron?
There is no direct interaction between dolasetron and alcohol on the label. In practice, alcohol makes the dizziness, lightheadedness, and drowsiness that dolasetron can cause noticeably worse, and it irritates a stomach that is already unsettled. Alcohol also worsens dehydration, which matters if you have been vomiting or are on chemotherapy. Skip alcohol on the day you take a dose and for the day or two around chemotherapy or surgery. If you drink daily and stopping is hard, mention it, because it changes what else is safe to prescribe.
Is dolasetron safe during pregnancy or breastfeeding?
The FDA labeling reports that there are no adequate and well controlled studies of dolasetron in pregnant people, so the risk is not established either way. There is also no data on whether dolasetron passes into human breast milk or affects a nursing infant. That means the decision is made case by case, weighing how severe the nausea is and what the alternatives are. Tell your clinician if you are pregnant, might be, or are nursing before the dose is given, not after. Dolasetron is not a treatment for morning sickness, and pregnancy nausea is managed with different first-line options.
Do I take dolasetron with food?
You can take dolasetron with or without food; a meal does not meaningfully change how it works. Swallow the tablet with a full glass of water. What matters more is the timing: take it within one hour before chemotherapy starts, or within two hours before surgery, so it is already working when the trigger hits. If you are told to fast before a procedure, take the tablet with the small sip of water your surgical team allows. If you vomit within a few minutes of swallowing the tablet, do not automatically repeat it; call your team first.
What are the signs of a dolasetron overdose?
Too much dolasetron can cause severe dizziness, a sharp drop in blood pressure, fainting, and abnormal heart rhythms, including a very fast, very slow, or irregular heartbeat. Symptoms can start within a few hours of the extra dose. Call Poison Control at 1-800-222-1222 right away if you or someone else has taken more than prescribed, even if the person feels fine, and call 911 for collapse, seizure, chest pain, or trouble breathing. There is no specific antidote, so treatment is heart monitoring and supportive care in a medical setting. Keep the bottle with you so the exact strength and count can be checked.
What medicines interact with dolasetron?
The biggest concerns are other drugs that prolong the QT interval, including antiarrhythmics, methadone, some antipsychotics, and certain antibiotics, because the effects add up on the heart. Diuretics and anything causing low potassium or low magnesium raise the same risk, so those levels are usually checked and corrected first. Serotonin drugs such as SSRIs, SNRIs, tricyclics, triptans, MAO inhibitors, linezolid, lithium, tramadol, fentanyl, and St. John's wort can combine with dolasetron to cause serotonin syndrome. Cimetidine raises levels of the active form, rifampin lowers them, and atenolol slows its clearance. Bring a full list of prescriptions, over the counter products, and supplements so these can be checked before your dose.