Drug General Information (ID: DDIQ6DNRYL)
Drug Name			Erlotinib		Drug Info		Ranitidine (bismuth citrate)		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antineoplastics				Antiulcer Agents
Structure

Mechanism of Erlotinib-Ranitidine (bismuth citrate) Interaction (Severity Level: Moderate)
Altered gastric pH Click to Show/Hide Mechanism Graph
Drug Name		Erlotinib				Ranitidine (bismuth citrate)
Mechanism		Gastric pH sensitive				Gastric alkalinizer
Key Mechanism Factor 1
		Factor Name		Gastric pH
		Factor Description		The normal pH range of gastric acid is between 1.5 and 3.5 and is highly acidic, consisting mainly of hydrochloric acid. Changes in the pH of the stomach can alter the absorption of drugs.
Mechanism Description		Decreased absorption of Erlotinib due to altered gastric pH caused by Ranitidine (bismuth citrate)

Recommended Action
Management		In general, the concomitant use of erlotinib with agents that increase gastric pH should be avoided whenever possible. If acid-suppression therapy is required during erlotinib treatment, an H2-receptor antagonist such as ranitidine may be considered. Available pharmacokinetic data suggest that erlotinib should be administered once a day, at least 2 hours before or 10 hours after dosing of the H2-receptor antagonist. Additionally, the lowest effective dosage of the H2-receptor antagonist should be prescribed. It may be appropriate to avoid using cimetidine for long-term acid suppression, as it may inhibit the CYP450 3A4-mediated metabolism of erlotinib and increase the risk of toxicity.

References
1	Cerner Multum, Inc. "Australian Product Information.".
2	Cerner Multum, Inc. "UK Summary of Product Characteristics.".
3	Duong S, Leung M "Should the concomitant use of erlotinib and acid-reducing agents be avoided? The drug interaction between erlotinib and acid-reducing agents." J Oncol Pharm Pract 17 (2011): 448-52. [PMID: 20716581]