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Zofran Side Effects Center

Medical Editor: Eni Williams, PharmD, PhD

Last reviewed on RxList 4/8/2015

Zofran (Ondansetron) is a medication that belongs to the drug class known as antiemetic and selective 5-HT3 receptor antagonist. Zofran is prescribed for the treatment of nausea and vomiting due to cancer chemotherapy and also used to prevent and treat nausea and vomiting after surgery. Common side effects of Zofran include diarrhea, headache, fever, lightheadedness, dizziness, drowsiness, constipation, rash, blurred vision and muscle spasm.

Zofran adult dose is 32-mg given as a single dose or divided in three 0.15-mg/kg divided doses infused over 15 minutes. Drug interactions include Ultram (tramadol) and cytochrome P-450 enzyme inhibitors or inducers including Dilantin (phenytoin), Tegretol (carbamazepine), and rifadin (rifampin). Zofran should not be used during pregnancy unless the benefits outweigh the risks. It is not known if Zofran is excreted in breast milk.

Our Zofran Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Zofran in Detail - Patient Information: Side Effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • blurred vision or temporary vision loss (lasting from only a few minutes to several hours);
  • severe dizziness, feeling short of breath, fainting, fast or pounding heartbeats;
  • slow heart rate, trouble breathing;
  • anxiety, agitation, shivering;
  • feeling like you might pass out; or
  • urinating less than usual or not at all.

Less serious side effects may include:

  • diarrhea or constipation;
  • weakness or tired feeling;
  • fever;
  • headache; or
  • dizziness, drowsiness.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Zofran (Ondansetron Hydrochloride)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Zofran Overview - Patient Information: Side Effects

SIDE EFFECTS: Headache, lightheadedness, dizziness, drowsiness, tiredness, or constipation may occur. If these effects persist or worsen, notify your doctor promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: stomach pain, muscle spasm/stiffness, vision changes (e.g., temporary loss of vision, blurred vision).

Get medical help right away if any of these rare but very serious side effects occur: chest pain, slow/fast/irregular heartbeat, severe dizziness, fainting.

This medication may increase serotonin and rarely cause a very serious condition called serotonin syndrome/toxicity. The risk increases if you are also taking other drugs that increase serotonin, so tell your doctor or pharmacist of all the drugs you take (see Drug Interactions section). Get medical help right away if you develop some of the following symptoms: fast heartbeat, hallucinations, loss of coordination, severe dizziness, severe nausea/vomiting/diarrhea, twitching muscles, unexplained fever, unusual agitation/restlessness.

A very serious allergic reaction to this drug is unlikely, but stop taking this medication and seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Zofran (Ondansetron Hydrochloride)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Zofran FDA Prescribing Information: Side Effects
(Adverse Reactions)


The following have been reported as adverse events in clinical trials of patients treated with ondansetron, the active ingredient of ZOFRAN. A causal relationship to therapy with ZOFRAN has been unclear in many cases.

Chemotherapy-Induced Nausea and Vomiting

The adverse events in Table 5 have been reported in ≥ 5% of adult patients receiving a single 24-mg ZOFRAN Tablet in 2 trials. These patients were receiving concurrent highly emetogenic cisplatin-based chemotherapy regimens (cisplatin dose ≥ 50 mg/m ).

Table 5: Principal Adverse Events in US Trials: Single Day Therapy With 24-mg ZOFRAN Tablets (Highly Emetogenic Chemotherapy)

Event Ondansetron 24 mg q.d.
n = 300
Ondansetron 8 mg b.i.d.
n = 124
Ondansetron 32 mg q.d.
n = 117
Headache 33 (11%) 16 (13%) 17 (15%)
Diarrhea 13 (4%) 9 (7%) 3 (3%)

The adverse events in Table 6 have been reported in ≥ 5% of adults receiving either 8 mg of ZOFRAN Tablets 2 or 3 times a day for 3 days or placebo in 4 trials. These patients were receiving concurrent moderately emetogenic chemotherapy, primarily cyclophosphamide-based regimens.

Table 6: Principal Adverse Events in US Trials: 3 Days of Therapy With 8-mg ZOFRAN Tablets (Moderately Emetogenic Chemotherapy)

Event Ondansetron 8 mg b.i.d.
n = 242
Ondansetron 8 mg t.i.d.
n = 415
n = 262
Headache 58 (24%) 113 (27%) 34 (13%)
Malaise/fatigue 32 (13%) 37 (9%) 6 (2%)
Constipation 22 (9%) 26 (6%) 1 ( < 1%)
Diarrhea 15 (6%) 16 (4%) 10 (4%)
Dizziness 13 (5%) 18 (4%) 12 (5%)

Central Nervous System: There have been rare reports consistent with, but not diagnostic of, extrapyramidal reactions in patients receiving ondansetron.

Hepatic: In 723 patients receiving cyclophosphamide-based chemotherapy in US clinical trials, AST and/or ALT values have been reported to exceed twice the upper limit of normal in approximately 1% to 2% of patients receiving ZOFRAN Tablets. The increases were transient and did not appear to be related to dose or duration of therapy. On repeat exposure, similar transient elevations in transaminase values occurred in some courses, but symptomatic hepatic disease did not occur. The role of cancer chemotherapy in these biochemical changes cannot be clearly determined.

There have been reports of liver failure and death in patients with cancer receiving concurrent medications including potentially hepatotoxic cytotoxic chemotherapy and antibiotics. The etiology of the liver failure is unclear.

Integumentary: Rash has occurred in approximately 1% of patients receiving ondansetron.

Other: Rare cases of anaphylaxis, bronchospasm, tachycardia, angina (chest pain), hypokalemia, electrocardiographic alterations, vascular occlusive events, and grand mal seizures have been reported. Except for bronchospasm and anaphylaxis, the relationship to ZOFRAN was unclear.

Radiation-Induced Nausea and Vomiting

The adverse events reported in patients receiving ZOFRAN Tablets and concurrent radiotherapy were similar to those reported in patients receiving ZOFRAN Tablets and concurrent chemotherapy. The most frequently reported adverse events were headache, constipation, and diarrhea.

Postoperative Nausea and Vomiting

The adverse events in Table 7 have been reported in ≥ 5% of patients receiving ZOFRAN Tablets at a dosage of 16 mg orally in clinical trials. With the exception of headache, rates of these events were not significantly different in the ondansetron and placebo groups. These patients were receiving multiple concomitant perioperative and postoperative medications.

Table 7: Frequency of Adverse Events From Controlled Studies With ZOFRAN Tablets (Postoperative Nausea and Vomiting)

Adverse Event Ondansetron 16 mg
(n = 550)
(n = 531)
Wound problem 152 (28%) 162 (31%)
Drowsiness/sedation 112 (20%) 122 (23%)
Headache 49 (9%) 27 (5%)
Hypoxia 49 (9%) 35 (7%)
Pyrexia 45 (8%) 34 (6%)
Dizziness 36 (7%) 34 (6%)
Gynecological disorder 36 (7%) 33 (6%)
Anxiety/agitation 33 (6%) 29 (5%)
Bradycardia 32 (6%) 30 (6%)
Shiver(s) 28 (5%) 30 (6%)
Urinary retention 28 (5%) 18 (3%)
Hypotension 27 (5%) 32 (6%)
Pruritus 27 (5%) 20 (4%)

Preliminary observations in a small number of subjects suggest a higher incidence of headache when ZOFRAN ODT Orally Disintegrating Tablets are taken with water, when compared to without water.

Observed During Clinical Practice

In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of oral formulations of ZOFRAN. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. The events have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to ZOFRAN.

Cardiovascular: Rarely and predominantly with intravenous ondansetron, transient ECG changes including QT interval prolongation have been reported.

General: Flushing. Rare cases of hypersensitivity reactions, sometimes severe (e.g., anaphylaxis/anaphylactoid reactions, angioedema, bronchospasm, shortness of breath, hypotension, laryngeal edema, stridor) have also been reported. Laryngospasm, shock, and cardiopulmonary arrest have occurred during allergic reactions in patients receiving injectable ondansetron.

Hepatobiliary: Liver enzyme abnormalities

Lower Respiratory: Hiccups

Neurology: Oculogyric crisis, appearing alone, as well as with other dystonic reactions

Skin: Urticaria, Stevens-Johnson syndrome, and toxic epidermal necrolysis.

Special Senses: Eye Disorders: Cases of transient blindness, predominantly during intravenous administration, have been reported. These cases of transient blindness were reported to resolve within a few minutes up to 48 hours.

Drug Abuse And Dependence

Animal studies have shown that ondansetron is not discriminated as a benzodiazepine nor does it substitute for benzodiazepines in direct addiction studies.

Read the entire FDA prescribing information for Zofran (Ondansetron Hydrochloride)

Zofran - User Reviews

Zofran User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Zofran sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


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