Before using ondansetron,
tell your doctor and pharmacist if you are allergic to ondansetron, alosetron (Lotronex), dolasetron (Anzemet), granisetron (Kytril), palonosetron (Aloxi), or any other medications: or any of the ingredients in ondansetron injection. Ask your pharmacist for a list of the ingredients.
tell your doctor if you are receiving apomorphine (Apokyn). Your doctor will probably tell you not to use ondansetron if you are receiving this medication.
tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: amiodarone (Cordarone, Pacerone); azithromycin (Zithromax); certain medications for seizures such as carbamazepine (Carbatrol, Epitol, Equetro, Tegretol), or phenytoin (Dilantin); chloroquine (Aralen); chlorpromazine ; citalopram (Celexa); clarithromycin (Biaxin, in Prevpac); diuretics ('water pills'); erythromycin (E.E.S., Erythrocin, others); fentanyl (Abstral, Actiq, Duragesic, Fentora, Lazanda, Onsolis, Subsys); flecainide; haloperidol (Haldol); lithium (Lithobid); medications to treat migraines such as almotriptan (Axert), eletriptan (Relpax), frovatriptan (Frova), naratriptan (Amerge), rizatriptan (Maxalt), sumatriptan (Imitrex), and zolmitriptan (Zomig); methylene blue; mirtazapine (Remeron); monoamine oxidase (MAO) inhibitors including isocarboxazid (Marplan), linezolid (Zyvox), phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar), and tranylcypromine (Parnate); moxifloxacin (Avelox); pentamidine (Nebu-Pent); pimozide (Orap); procainamide; quinidine; rifampin (Rifadin, Rimactane, in Rifamate, in Rifater); selective serotonin/norepinephrine reuptake inhibitors (SNRIs) such as desvenlafaxine (Khedezla, Pristiq), duloxetine (Cymbalta), and venlafaxine (Effexor XR); selective serotonin reuptake inhibitors (SSRIs) such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac, Sarafem, in Symbyax), fluvoxamine (Luvox), paroxetine (Brisdelle, Paxil, Pexeva), and sertraline (Zoloft); sotalol (Betapace, Sorine); thioridazine; tramadol (Conzip, Ultram, in Ultracet); and vandetanib (Caprelsa). Your doctor may need to change the doses of your medications or monitor you more carefully for side effects. Many other medications may also interact with ondansetron, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
tell your doctor if you or anyone in your family has or has ever had long QT syndrome (condition that increases the risk of developing an irregular heartbeat that may cause fainting or sudden death), or another type of irregular heart beat or heart rhythm problem, or if you have or have ever had low levels of magnesium or potassium in your blood, heart failure (HF; condition in which the heart cannot pump enough blood to other parts of the body), or liver disease.
tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while receiving ondansetron, call your doctor.