Classification: Tyrosine Kinase Inhibitors
Lapatinib belongs to a class of drugs known as tyrosine kinase inhibitors. Tyrosine kinase inhibitors are designed to block the action of a specific enzyme called tyrosine kinase. This enzyme plays a big role in the function of cells, and is active in cancer cells to promote tumor growth and progression. Lapatinib works to inhibit the function of two types of tyrosine kinases: epidermal growth factor receptor (EGFR) and Her2. EGFR is over expressed in several types of tumors and Her2 is over expressed in about 25-30% of all breast cancers. By blocking the function of these tyrosine kinases, Lapatinib may prevent cancer cells from dividing and growing.
Lapatinib is taken in a tablet form, by mouth, once a day. The dose will consist of several tablets. It should be taken one hour before or one hour after a meal. Take lapatinib at around the same time every day. If you miss a dose, do not double the next dose to make up for the missed dose. Avoid grapefruit or grapefruit juice while you are on this therapy as it can interfere with how the medication is absorbed.
There are a number of things you can do to manage the side effects of Lapatinib. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:
Diarrhea is a common side effect of lapatinib and is potentially dangerous because it can lead to serious dehydration. Diarrhea can be defined as an increase in the number of bowel movements you have in a day. Your healthcare team will tell you how to take loperamide (an anti-diarrheal medication), which you should start taking as soon as diarrhea develops. Notify your healthcare team if the diarrhea does not stop on this medication so they can help you better manage this side effect.
Your oncology team can recommend medications to relieve diarrhea. Also, try eating low-fiber, bland foods, such as white rice and boiled or baked chicken. Avoid raw fruits, vegetables, whole grain breads, cereals and seeds. Soluble fiber is found in some foods that absorbs fluid and can help relieve diarrhea. Foods high in soluble fiber include: applesauce, bananas (ripe), canned fruit, orange and grapefruit sections, boiled potatoes, white rice and products made with white flour, oatmeal, cream of rice, cream of wheat, and farina. Drink 8-10 glasses on non-alcoholic, un-caffeinated fluid a day to prevent dehydration. Try sports drinks to replace electrolytes. Read Low Fiber Diet for Diarrhea for more tips.
Lapatinib has some unique nail and skin side effects that you may develop. Patients may develop a rash. While this rash may look like acne, it is not, and should not be treated with acne medications. The rash may appear red, swollen, crusty and dry and feel sore. You may also develop very dry skin, which may crack, be itchy or become flaky or scaly. The rash typically starts in the first week of treatment, but can occur at any time during treatment. Tips for managing your skin include:
While receiving lapatinib, you may develop an inflammation of the skin around the nail bed/cuticle areas of toes or fingers, which is called paronychia. It can appear red, swollen or pus filled. Nails may develop "ridges" in them or fall off. You may also develop cuts or cracks that look like small paper cuts in the skin on your toes, fingers or knuckles. These side effects may appear several months after starting treatment, but can last for many months after treatment stops.
Take anti-nausea medications as prescribed. If you continue to have nausea or vomiting, notify your doctor or nurse so they can help you manage this side effect. In addition, dietary changes may help. Avoid things that may worsen the symptoms, such as heavy or greasy/fatty, spicy or acidic foods (lemons, tomatoes, oranges). Try antacids, (e.g. milk of magnesia, calcium tablets such as Tums), saltines, or ginger ale to lessen symptoms. Read the Nausea & Vomiting Tip Sheet for more suggestions.
Call your doctor or nurse if you are unable to keep fluids down for more than 12 hours or if you feel lightheaded or dizzy at any time.
Lapatinib is known to cause cardiac (heart) dysfunction, including severe heart failure (congestive heart failure). Patients should have their heart function tested prior to starting this therapy and during therapy if any symptoms arise. If heart function decreases, lapatinib should be stopped. You should report to your healthcare team any symptoms of cardiac dysfunction, including: feeling like your heart is racing or pounding, dizziness, unusual tiredness, lightheadedness or shortness of breath.
HFS is a skin reaction that appears on the palms of the hands and/or the soles of the feet as a result of certain chemotherapy agents. It can start as a feeling of tingling or numbness in the palms and/or soles and progress to swelling, redness, peeling skin, and tenderness or pain. Notify your healthcare team right away if you notice any of these signs of HFS. Learn more about HFS on OncoLink.
Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant or father a child while on this medication. Effective birth control is necessary during treatment, even if your menstrual cycle stops or you believe your sperm is affected. It is not known if this medication passes into breast milk and harm a baby, therefore you should not breastfeed while taking this medication.
Some patients experience an allergic reaction to this medication and should stop taking the medication immediately. Lapatinib can affect your liver function. Your doctor will check your liver function with blood tests. You should notify your healthcare team if you develop itchy skin, yellowing of your skin or eyes, your urine becomes dark or you develop pain in the abdomen.
Lapatinib can cause lung conditions called interstitial lung disease and pneumonitis. Notify your healthcare team if you develop shortness of breath or a cough that won’t go away.
Be sure to let your healthcare team know any other medications, supplements, vitamins or herbs you may be taking, as some can interfere with the absorption of lapatinib.