Take this medication by mouth on an empty stomach (at least 1 hour before or 2 hours after a meal) as directed by your doctor, usually once daily.

The dosage is based on your medical condition, response to treatment, and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Medications that reduce stomach acid (such as antacids, proton pump inhibitors/PPIs, H2 blockers) may make erlotinib work less well. Do not take PPIs (such as lansoprazole, omeprazole) while using this medication. If you take H2 blockers (such as famotidine, nizatidine), take erlotinib at least 2 hours before or 10 hours after taking the H2 blocker. If you take antacids, take erlotinib several hours before or after taking the antacid.

Avoid eating grapefruit or drinking grapefruit juice while using this medication unless your doctor or pharmacist says you may do so safely. Grapefruit can increase the chance of side effects with this medicine. Ask your doctor or pharmacist for more details.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.

Do not increase your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of serious side effects will increase.

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.