Ondansetron

The recommended adult dose of ondansetron for nausea and vomiting caused by chemotherapy is based on severity of the symptoms and ranges from 8 mg to 24 mg daily given in divided doses.

Doses for children are based on body size. The recommended dose for children is 3 to 5 mg per square metre of body surface area and will be calculated by your doctor.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the one given here, do not change the way that you are taking the medication without consulting your doctor.

Ondansetron should be taken ½ to 1 hour before chemotherapy treatment. After this first dose, it should be taken every 8 to 12 hours for up to 5 days.

Use an oral syringe to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.

The recommended adult dose of ondansetron to treat and prevent nausea and vomiting caused by radiation therapy is 8 mg taken by mouth, 1 to 2 hours before treatment, and then every 8 hours for up to 5 days after treatment.

The recommended adult dose of ondansetron to prevent nausea and vomiting caused by surgery is 16 mg taken by mouth, 1 hour before anesthesia. Alternatively a dose of 4 mg may be given by intravenous (into a vein) injection at the time of surgery. After surgery, a single dose of 4 mg of ondansetron may be given by intravenous injection to treat nausea or vomiting.

Ondansetron is not effective for treating or preventing nausea and vomiting caused by motion.

It is important to take Ondansetron exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store all forms of Ondansetron at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

In addition to its desired action, this medication may cause some adverse effects, notably: it may cause headaches; it may cause diarrhea or constipation, depending on the person; it may cause drowsiness or dizziness - use caution when getting up from a lying or sitting position and use caution if driving; it may cause unusual tiredness. Each person may react differently to a treatment. If you think this medication may be causing adverse effects (including those described here, or others), talk to your health care professional. He or she can help you to determine whether or not the medication is the source of the problem.

4 mg
Each yellow, oval-shaped, film-coated tablet, imprinted "P" on one side and "4" on the other, contains 4 mg ondansetron as ondansetron hydrochloride dihydrate. Nonmedicinal ingredients: cornstarch, croscarmellose sodium, iron oxide yellow, lactose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.

8 mg
Each yellow, oval-shaped, film-coated tablet, imprinted "P" on one side and "8" on the other side, contains 8 mg ondansetron as ondansetron hydrochloride dihydrate. Nonmedicinal ingredients: cornstarch, croscarmellose sodium, iron oxide yellow, lactose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.

Do not take Ondansetron if you:

• are allergic to ondansetron or any ingredients of the medication
• are taking the medication Apomorphine

There may be an interaction between ondansetron and any of the following:

• alpha-blockers (e.g., Alfuzosin, Doxazosin, Tamsulosin)
• Amiodarone
• antipsychotics (e.g., chlorpromazine, Clozapine, Haloperidol, Olanzapine, pimozide, Quetiapine, Risperidone)
• Apalutamide
• apomorphine
• "azole" antifungals (e.g., fluconazole, itraconazole, ketoconazole, Voriconazole)
• barbiturates (e.g., pentobarbital, Phenobarbital)
• Bosentan
• Bromocriptine
• Buspirone
• Carbamazepine
• Carvedilol
• chloroquine
• Cobicistat
• Cyclobenzaprine
• Cyclosporine
• Deferasirox
• Degarelix
• Dexamethasone (systemic)
• Dipyridamole
• Disopyramide
• dofetilide
• Domperidone
• Dronedarone
• Enzalutamide
• ergot alkaloids (e.g., ergotamine, Dihydroergotamine)
• Flecainide
• Flibanserin
• formoterol
• grapefruit juice
• Hepatitis C antivirals (e.g., daclatasvir, ledipasvir)
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• lithium
• Lomitapide
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• Maprotiline
• mefloquine
• Metformin
• Methadone
• mifepristone
• Mirtazapine
• Mitotane
• Modafinil
• monoamine oxidase inhibitors (M.O.S. e.g., Moclobemide, Rasagiline, Selegiline, Tranylcypromine)
• Phenytoin
• primidone
• procainamide
• Propafenone
• Propranolol
• quinidine
• quinine
• quinolone antibiotics (e.g., ciprofloxacin, Norfloxacin, Ofloxacin)
• rifabutin
• rifampin
• rilpivirine
• Romidepsin
• St. John's wort
• saquinavir
• selective serotonin reuptake inhibitors (SSRIs; e.g., Citalopram, Fluoxetine, Paroxetine, Sertraline)
• serotonin/norepinephrine reuptake inhibitors (SNRIs; e.g., Desvenlafaxine, Duloxetine, Venlafaxine)
• other serotonin antagonist antiemetics (e.g., dolasetron, granisetron)
• siltuximab
• sotalol
• tacrolimus
• Tapentadol
• tenofovir
• Tetrabenazine
• Tocilizumab
• Tramadol
• Trazodone
• tricyclic antidepressants (e.g., Amitriptyline, Clomipramine, Desipramine, Trimipramine)
• "triptan" migraine medications (e.g., Rizatriptan, Sumatriptan, Zolmitriptan)
• Tryptophan
• tyrosine kinase inhibitors (e.g., Dabrafenib, imatinib, Nilotinib, Sunitinib)
• Vardenafil
• verapamil

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with Ondansetron. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the Nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use Ondansetron.

Allergy: People who have had an allergic reaction to Dolasetron or Granisetron are advised not to take ondansetron. Before you take ondansetron, inform your doctor about any previous adverse reactions you have had to medications. Contact your doctor at once if you experience signs of an allergic reaction such as skin rash, itching, difficulty breathing, or swelling of the face and throat.

Abnormal heart rhythms: Very rarely, ondansetron can affect the heart's electrical activity and cause an irregular heartbeat. This is more likely to happen with the injectable form of ondansetron. Certain medications (e.g., Sotalol, quinidine, thioridazine, Chlorpromazine, Pimozide, moxifloxacin, Mefloquine, pentamidine, arsenic trioxide, probucol, Tacrolimus) can increase the risk of a type of abnormal heart rhythm called QT prolongation, and should not be used in combination with ondansetron. You are more at risk for this type of abnormal heart rhythm and its complications if you:

• are female
• are older than 65 years of age
• have a family history of sudden cardiac death
• have a history of heart disease or abnormal heart rhythms
• have a slow heart rate
• have congenital prolongation of the QT interval
• have Diabetes
• have had a Stroke
• have low potassium, magnesium, or calcium levels
• have nutritional deficiencies

If you have heart disease and abnormal heart rhythms, or are taking certain medications (e.g., Verapamil, atazanavir), discuss with your doctor how Ondansetron may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Ondansetron, and whether any special monitoring is needed. Your doctor may monitor your heart rate using a test called an electrocardiogram (ECG) while you are using Ondansetron.

Liver function: Ondansetron is broken down and removed from the body by the liver. Decreased liver function slows down the removal of the medication from the body and increases the risk of side effects from ondansetron. If you have liver disease or reduced liver function, discuss with your doctor how Ondansetron may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Ondansetron, and whether any special monitoring is needed.

Motion Sickness: Ondansetron is not effective for the treatment of motion sickness.

Neuroleptic malignant syndrome (NMS): Ondansetron, like other similar medications, can cause a potentially fatal syndrome known as neuroleptic malignant syndrome (NMS). If you notice the symptoms of NMS such as high fever, muscle stiffness, confusion or loss of consciousness, sweating, racing or irregular heartbeat, or fainting, get immediate medical attention.

Phenylketonuria: People with phenylketonuria (lacking the enzyme needed to break down phenylalanine) should take forms of ondansetron other than oral dissolving tablets (ODT). The ODT form of ondansetron contains aspartame, an ingredient that cannot be broken down in the body by people who have phenylketonuria.

Serotonin syndrome: Severe reactions are possible when ondansetron is combined with other medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors, medications used to treat Depression. These combinations must be avoided. Symptoms of a reaction may include muscle rigidity and spasms, difficulty moving, and changes in mental state including delirium and agitation. Coma and death are possible.

Pregnancy: The safety of ondansetron for use by pregnant women has not been established. Ondansetron should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Ondansetron, contact your doctor immediately.

Breast-feeding: It is not known if ondansetron passes into breast milk. If you are a breast-feeding mother and are taking Ondansetron, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using Ondansetron to treat nausea and vomiting caused by chemotherapy have not been established for children under 3 years of age. The safety and effectiveness of using Ondansetron to treat nausea and vomiting caused by radiation or surgery have not been determined for children less than 18 years of age. Its use by this age group is not recommended.

Seniors: The safety and effectiveness of using Ondansetron by people 65 years or older to treat nausea and vomiting caused by surgery have not been established. Seniors may be at an increased risk of developing irregular heart beat with ondansetron, particularly the injectable form. Talk to your doctor about any concerns you may have.

Avoid touching the tablet or take it with dry hands. Place the tablet on your tongue and allow it to melt. Then swallow it with your saliva. This medication is typically used every 8 hours. However, your pharmacist may have suggested a different schedule that is more appropriate for you. Important: Follow the instructions on the label. Do not use more of this product, or more often, than prescribed. This medication may be taken with or without food.