Why is this medication prescribed?
Imatinib is used to treat certain types of leukemia (cancer that begins in the white blood cells) and other cancers of the blood cells. Imatinib is also used to treat gastrointestinal stromal tumors (GIST; a type of tumor that grows in the walls of the digestive passages and may spread to other parts of the body). Imatinib is also used to treat dermatofibrosarcoma protuberans (a tumor that forms under the top layer of skin) when the tumor cannot be removed surgically, has spread to other parts of the body, or has come back after surgery. Imatinib is in a class of medications called kinase inhibitors. It works by blocking the action of the abnormal protein that signals cancer cells to multiply. This helps stop the spread of cancer cells.
How should this medicine be used?
Imatinib comes as a tablet to take by mouth. It is usually taken with a meal and a large glass of water once or twice a day. Take imatinib at around the same time(s) every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take imatinib exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
If you are unable to swallow imatinib tablets, you may place all of the tablets that you need for one dose into a glass of water or apple juice. Use 50 milliliters (a little less than 2 ounces) of liquid for each 100-mg tablet and 100 milliliters (a little less than 4 ounces) of liquid for each 400-mg tablet. Stir with a spoon until the tablets crumble completely and drink the mixture immediately.
If your doctor has told you to take 800 mg of imatinib, you should take 2 of the 400-mg tablets. Do not take 8 of the 100-mg tablets. The tablet coating contains iron, and you will receive too much iron if you take 8 of the 100-mg tablets.
Your doctor may increase or decrease your dose of imatinib during your treatment. This depends on how well the medication works for you and on the side effects you experience. Talk to your doctor about how you are feeling during your treatment. Continue to take imatinib even if you feel well. Do not stop taking imatinib without talking to your doctor.
Other uses for this medicine
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
What special precautions should I follow?
Before taking imatinib,
- tell your doctor and pharmacist if you are allergic to imatinib or any other medications.
- tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Be sure to mention any of the following: acetaminophen (Tylenol); certain antibiotics including erythromycin (E.E.S., E-Mycin, Erythrocin), clarithromycin (Biaxin), and rifampin (Rifadin, in Rifamate); anticoagulants ('blood thinners') such as warfarin (Coumadin); antifungals such as ketoconazole (Nizoral) and itraconazole (Sporanox); calcium channel blockers such as amlodipine (Norvasc, in Caduet), diltiazem (Cardizem, Tiazac), felodipine (Plendil), isradipine (Dynacirc), nicardipine (Cardene), nifedipine (Adalat, Procardia, others), nimodipine (Nimotop), nisoldipine (Sular), or verapamil (Calan, Covera, Isoptin, Verelan); cholesterol-lowering medications (statins) such as atorvastatin (Lipitor), lovastatin (Mevacor), and simvastatin (Zocor); cyclosporine (Neoral, Sandimmune); dexamethasone; hormonal contraceptives (birth control pills, patches, rings, injections or implants); pimozide (Orap); medications for anxiety; medications for seizures such as carbamazepine (Tegretol), phenobarbital, and phenytoin (Dilantin); sedatives; sleeping pills; and tranquilizers. Other medications may also interact with imatinib, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
- tell your doctor what herbal products you are taking, especially St. John's wort.
- tell your doctor if you have or have ever had high blood pressure; a heart attack; an irregular heartbeat; diabetes; or heart, lung, thyroid, or liver disease. Also tell your doctor if you smoke, if you use street drugs, and if you drink or have ever drunk large amounts of alcohol.
- tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while you are taking imatinib. Talk to your doctor about birth control methods that you can use during your treatment. If you become pregnant while taking imatinib, call your doctor. Imatinib may harm the fetus.
- tell your doctor if you are breast-feeding. You should not breast-feed while you are taking imatinib.
- talk to your doctor about what you should do if you develop diarrhea during your treatment. Do not take any medications to treat diarrhea without talking to your doctor.
What special dietary instructions should I follow?
Talk to your doctor about drinking grapefruit juice or eating grapefruit while taking this medication.
What should I do if I forget a dose?
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What side effects can this medication cause?
Imatinib may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- loss of appetite
- joint pain
- muscle cramps
- night sweats
- teary eyes
Some side effects can be serious. If you experience any of these symptoms call your doctor immediately:
- puffiness under the eyes
- swelling of the hands, feet, ankles, or lower legs
- weight gain
- shortness of breath
- fast, irregular, or pounding heartbeat
- difficulty falling asleep or staying asleep
- coughing up pink or bloody mucus
- increased urination, especially at night
- chest pain
- rash or blisters
- yellowing of the skin or eyes
- blood in the stool
- unusual bruising or bleeding
- sore throat, fever, chills, and other signs of infection
- excessive tiredness or weakness
Imatinib may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.
What should I know about storage and disposal of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of emergency/overdose
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
Symptoms of overdose may include:
- muscle cramps
- swollen or bloated stomach
What other information should I know?
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to imatinib.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.