SIDE EFFECTS: Diarrhea, dry skin, muscle/joint pain, mouth sores, unusual eyelash growth, or eye dryness/redness/irritation may occur. Diarrhea can be severe. In some cases, your doctor may prescribe medication to relieve diarrhea. If any of these effects last or get worse, tell your doctor or pharmacist 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 right away if you have any serious side effects, including: signs of kidney problems (such as change in the amount of urine), signs of liver disease (such as nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine), signs of dehydration (such as extreme thirst, muscle cramps, dizziness, fainting), redness/swelling around the nails, black stools, vomit that looks like coffee grounds, easy bleeding/bruising, unusual tiredness, eye pain, vision changes. Get medical help right away if you have any very serious side effects, including: new or worsening shortness of breath or cough, chest/jaw/left arm pain, weakness on one side of the body, trouble speaking, confusion, seizures. Erlotinib can commonly cause a mild rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe allergic reaction. Get medical help right away if you develop any rash. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: 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 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking erlotinib, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver disease, kidney disease, stomach/intestinal disease (such as ulcers, diverticulosis). Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). This medicine may cause stomach bleeding. Daily use of alcohol while using this medicine may increase your risk for stomach bleeding. Limit alcoholic beverages. Sunlight may worsen any skin reactions that may occur while you are taking this drug. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets. Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using erlotinib. Erlotinib may harm an unborn baby. Ask about reliable forms of birth control while using this medication and for 1 month after stopping treatment. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication. It is unknown if this drug passes into breast milk. Because of the possible risk to the infant, breast-feeding while using this drug and for 2 weeks after stopping treatment is not recommended. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: See also How to Use section. Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. Some products that may interact with this drug are: "blood thinners" (such as warfarin), drugs that lower stomach acid (such as proton pump inhibitors including omeprazole). Check all prescription and nonprescription medicine labels carefully since many medications contain pain relievers/fever reducers (aspirin, NSAIDs such as ibuprofen or naproxen) which may increase your risk for stomach bleeding while you are taking erlotinib. However, if your doctor has directed you to take low-dose aspirin to prevent heart attack or stroke (usually at dosages of 81-325 milligrams a day), you should keep taking the aspirin unless your doctor instructs you otherwise. Ask your doctor or pharmacist for more details. Cigarette smoking decreases blood levels of this medication. Tell your doctor if you smoke or if you have recently stopped smoking.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.