Erlotinib inhibits the intracellular phosphorylation of tyrosine kinase associated with EGFR, which also is expressed on cancer cells.

Recommended dose is 150 mg daily at least one hour before or two hours after the ingestion of food. Treatment should continue until disease progression or unacceptable toxicity occurs. Dose adjustments may be necessary for hepatic impairment and drug interactions. If dose reduction is necessary, reduce in 50 mg decrements.

Indicated in locally advanced or metastatic non-small cell lung cancer after failure of at least one prior chemotherapy regimen. Also approved in combination with gemcitabine for the treatment of locally advanced, unresectable or metastatic pancreatic carcinoma.

Rash and diarrhea may be severe (grade 3–4). Other effects include anorexia, fatigue, and dyspnea. Abnormal liver function tests may be transient or associated with liver metastases. GI bleeding, conjunctivitis, and keratitis have occurred. Rare reports of serious Interstitial Lung Disease.

Educate patient to report severe or persistent diarrhea, nausea, anorexia or vomiting, worsening of unexplained shortness of breath or cough, and eye irritation.

Co-treatment with ketoconazole or other potent CYP3A4 inhibitors may increase erlotinib levels, requiring a lower dose.

Pre-treatment with rifampicin and other CYP3A4 inducers (includes phenytoin, phenobarbital, and St. John’s wort) may decrease erlotinib activity, requiring an increased dose.

Monitor liver function tests, and consider dose reductions for abnormal tests, including INR, especially if the patient is on warfarin.

Monitor patient for signs of GI bleeding and elevated INR. Patients on anticoagulants should be monitored for changes in PT and INR.

Diarrhea can usually be managed with loperamide. Both diarrhea and severe skin reactions may require dose reduction or temporary interruption of therapy.

In patients who develop an acute onset of new or progressive pulmonary symptoms (dyspnea, cough, or fever), therapy should be interrupted pending diagnostic evaluation. If ILD is diagnosed, discontinue therapy and treat patient as needed.