Drug General Information (ID: DDI4NYXRUJ)
Drug Name			Ranitidine		Drug Info		Atazanavir		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antiulcer Agents				Anti-Hiv Agents
Structure

Mechanism of Ranitidine-Atazanavir Interaction (Severity Level: Major)
Altered gastric pH Click to Show/Hide Mechanism Graph
Drug Name		Ranitidine				Atazanavir
Mechanism		Gastric alkalinizer				Gastric pH sensitive
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 Atazanavir due to altered gastric pH caused by Ranitidine

Recommended Action
Management		When used with atazanavir/cobicistat or atazanavir/ritonavir once daily in adults, the dosage of the H2-receptor antagonist should be no more than the equivalent of famotidine 40 mg twice daily in antiretroviral treatment-naive patients and 20 mg twice daily in treatment-experienced patients. Atazanavir/cobicistat or atazanavir/ritonavir should be administered simultaneously with, and/or at least 10 hours after, the H2-receptor antagonist. If tenofovir is also prescribed, no additional precaution is necessary in treatment-naive patients, whereas the dosage of atazanavir/ritonavir should be increased to 400 mg/100 mg once a day in treatment-experienced patients. All three antiretroviral agents should be administered as a single daily dose with food. In the event that ritonavir is not tolerated by a treatment-naive patient, atazanavir may be administered at an increased dosage of 400 mg once daily at least 2 hours before and at least 10 hours after the H2-receptor antagonist.

References
1	Cerner Multum, Inc. "UK Summary of Product Characteristics.".
2	Drug interactions. Atazanavir and acid-reducing agents. TreatmentUpdate 18 (2006): 4. [PMID: 17209238]
3	Klein CE, Chiu YL, Cai Y, et al. "Effects of Acid-reducing agents on the pharmacokinetics of lopinavir/ritonavir and ritonavir-boosted atazanavir." J Clin Pharmacol 48 (2008): 553-62. [PMID: 18440920]
4	Product Information. Evotaz (atazanavir-cobicistat). Bristol-Myers Squibb, Princeton, NJ.
5	Product Information. Reyataz (atazanavir). Bristol-Myers Squibb, Princeton, NJ.
6	Ray JE, Marriott D, Bloch MT, McLachlan AJ "Therapeutic drug monitoring of atazanavir: surveillance of pharmacotherapy in the clinic." Br J Clin Pharmacol 60 (2005): 291-9. [PMID: 16120068]
7	Agarwala S, Persson A, Eley T, et al "Effect of famotidine 20 and 40 mg dosing regimens on the bioavailability of atazanavir with ritonavir in combination with tenofovir in healthy subjects".
8	Durant J, Clevenbergh P, Garraffo R, Halfon P, Icard S, DelGiudice P, Montagne N, Schapiro JM, Dellamonica P "Importance of protease inhibitor plasma levels in HIV-infected patients treated with genotypic-guided therapy: pharmacological data from the Viradapt Study." Aids 14 (2000): 1333-9. [PMID: 10930147]