University of California, San Francisco Logo

University of California, San Francisco | About UCSF | Search UCSF | UCSF Medical Center

Home > Treatment > HIV Meds Quarterly > Spring 2008 > Concurrent Use of Atazanavir
Concurrent Use of Atazanavir and Acid-Lowering Medications

Atazanavir (ATV) requires an acidic gastric environment in order to be absorbed. H2-receptor blockers and proton pump inhibitors (PPIs) may cause decreases in serum ATV levels by neutralizing gastric acidity, and many data have demonstrated this effect. Although these data are heterogeneous, the adverse pharmacokinetic effect of acid-lowering medications on ATV appears to be greater:

With PPIs as opposed to H2 blockers (and the effect is much greater with both PPIs and H2 blockers than with antacids such as Rolaids, Tums, and Maalox)
When they are taken with unboosted ATV as opposed to ritonavir-boosted ATV (ATV/r)
When they are taken shortly before the ATV dose

Several dosing strategies for avoiding this pharmacokinetic effect have been tested, with varying results. A summary of data on these strategies can be found in the article referenced below. The manufacturer of ATV recently announced new recommendations for the use of ATV in patients taking acid-lowering medications. They are as follows:

Antiretroviral-Naive Patients

The use of unboosted ATV is not recommended.
H2 blockers: ATV/r 300/100 mg daily; H2 blocker dosage not to exceed the equivalent of famotidine 40 mg twice daily; give ATV/r with the H2 blocker, and/or >10 hours after the H2 blocker.
PPIs: ATV/r 300/100 mg daily; PPI dosage not to exceed the equivalent of omeprazole 20 mg once daily, with the PPI to be taken approximately 12 hours before ATV/r.

Antiretroviral-Experienced Patients (in whom higher serum ATV levels may be important for virologic efficacy)

The use of unboosted ATV is not recommended.
H2 blockers: if tenofovir is used in the regimen, give ATV/r 400/100 mg daily. Administer H2 blocker as for antiretroviral-naive patients, detailed above.
The use of PPIs is not recommended.

Antacids and buffered medications: ATV should be taken 2 hours before or 1 hour after these medications.

It should be noted that the data on which these recommendations are based are varied in their quality and their results. The virologic impact of the interactions between H2 blockers or PPIs and ATV remains unclear, as does the therapeutic effect of administering ATV with these agents according to the new recommendations. Pending further information, these medications should be used cautiously in patients taking ATV.


  1. Béique L, Giguère P, la Porte C, et al. Interactions between protease inhibitors and acid-reducing agents: a systematic review. HIV Med. 2007 Sep;8(6):335-45.
  2. Reyataz [patient information]. Princeton, NJ: Bristol-Myers Squibb Company; December 2007. Available at: Accessed February 27, 2008.