along with its therapeutic benefit, erlotinib may cause the following side effects:

• rash
• diarrhea
• lethargy
• nausea and vomiting
• loss of appetite
• mouth irritation
• stomach pain
• itching
• dry skin

Tell your doctor immediately if any of these rare but very serious side effects occur: black stools, vomit that looks like coffee grounds, easy bleeding/bruising, stomach/abdominal pain, yellowing eyes or skin, dark urine, unusual fatigue, signs of infection (e.g., fever, chills, persistent sore throat), eye pain, vision changes

Erlotinib is an Epidermal Growth Factor Receptor Tyrosine Kinase inhibitor.
The exact way that erlotinib works is not known. It is thought to work by suppressing epidermal growth factor receptor tyrosine kinase. This is a protein that is known to promote the growth and spread of cancer cells.

• Erlotinib should only be administered by a health care provider experienced in treating cancer.
• Before starting therapy, testing should be done to confirm the cancer cells have the EGFR mutation.
• Use erlotinib with caution if:
  • you have liver problems
  • you have kidney problems
  • you have gastrointestinal ulcers (bleeding of the stomach or intestines) or diverticular disease
  • you have cataracts, have had cataract surgery, or wear contact lenses
  • you have lung disease
  • you smoke tobacco  
• The following medications may interact with erlotinib:
  • Some antifungals (such as ketoconazole, fluconazole)
  • Calcium channel blockers
  • Macrolide antibiotics (such as erythromycin, clarithromycin)
  • Fluoroquinolone antibiotics (such as ciprofloxacin, norfloxacin)
  • Rifampin
  • Some antivirals (such as ritonavir, indinavir)
  • St. John’s Wort
  • Carbamazepine and phenytoin
  • Warfarin
  • Medications which reduce acid in the stomach (such as omeprazole, ranitidine)
  • Statin drugs to treat high cholesterol
• Erlotinib may cause diarrhea, nausea and vomiting. In some cases, these symptoms may be severe and therapy may need to be interrupted.
• Cases of interstitial lung disease have been reported in patients receiving erlotinib and some have been fatal. Notify your health care provider if you develop sudden changes in your breathing function such as shortness of breath, a new cough, or fever. If these symptoms develop, therapy with erlotinib may need to be interrupted.
• Development of a skin rash is a common adverse reaction to erlotinib. In a small number of patients this rash may be severe and may require discontinuation of treatment.

Erlotinib is not recommended for use during pregnancy. It may cause harm to a fetus or a miscarriage. Women of childbearing age should use reliable form(s) of birth control during treatment and for at least 2 weeks following the end of treatment with this drug.

It is not known whether this drug passes into breast milk. Breast-feeding while using this drug is not recommended.