Erlotinib is a tyrosine kinase inhibitor which reversibly inhibits the kinase activity of EGFR(Epidermal Growth Factor Receptor). It prevents autophosphorylation of tyrosine residues associated with the receptor and thereby inhibiting further downstream signaling. The absorption of this drug is 60%. Metabolism occurs in liver (CYP mediated, mainly CYP3A4 and a lesser extent by CYP1A2). This drug is eliminated by feces (83%) and urine (8%). It has a half-life (t1/2) of 36.2 hours.