Time to Virological Failure with Boosted Atazanavir (Reyataz) or Lopinavir/ritonavir (Kaletra) Is Not Affected by Use of H2 Receptor Blockers

Kaletra Tablet

Reyataz Capsule

Antiretroviral drugs have the potential to interact with many other types of medication, which could lead to either excessive levels in the body (possibly causing more side effects) or subtherapeutic levels that are unable to control HIV.

One class of drugs that may interact with protease inhibitors (PIs) are H2 receptor agonists, or H2 blockers, which reduce gastric acid production and are used to treat gastroesophageal reflux disease; these include cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac). Another class of drugs used for the same indication, proton pump inhibitors such as omeprazole (Prilosec) and esomeprazole (Nexium), may also interfere with PIs. This is particularly a concern with atazanavir (Reyataz), which requires adequate stomach acid for proper absorption.

To address this issue, investigators conducted a retrospective electronic database review to determine differences in rates of and time to virological failure among HIV patients concurrently taking H2 blockers while receiving antiretroviral regimens containing either ritonavir-boosted atazanavir or lopinavir/ritonavir (Kaletra).

Data were collected from October 2003 (when atazanavir became commercially available) through February 2006. Virological failure was defined as either 2 plasma HIV RNA levels > 400 copies/mL after at least 1 viral load measurement below the level of detection, or failure to achieve HIV RNA < 400 copies/mL within 24 weeks of starting therapy.

Results of the study appear in the August 2008 issue of the International Journal of STDs and AIDS:

Results

• Data from 267 patients receiving atazanavir/ritonavir were compared against those from 670 patients treated with lopinavir/ritonavir.

• Approximately 10% of the atazanavir/ritonavir group and 20% of the lopinavir/ritonavir group received concurrent H2 blockers.

• Multivariate analysis showed no statistically significant differences regarding time to virological failure between or among the 4 subgroups, after adjusting for differences in baseline characteristics (P = 0.79).

• 750 days following treatment initiation, the proportions of patients not experiencing virological failure were:

• 56% in the atazanavir/ritonavir with H2 blocker subgroup;

• 48% in the atazanavir/ritonavir without H2 blocker subgroup;

• 45% in the lopinavir/ritonavir without H2 blocker subgroup;

• 42% in the lopinavir/ritonavir with H2 blocker subgroup.

These findings led the investigators to conclude that the time to virological failure with atazanavir/ritonavir and lopinavir/ritonavir, with or without an H2 receptor blockers, was not significantly different in this observational database study.

Department of Internal Medicine, Division of Infectious Diseases, University of Texas Southwestern Medical Center, Dallas, TX.

9/12/08

Reference
PH Keiser and N Nassar. Time to virological failure with atazanavir/ritonavir and lopinavir/ritonavir, with or without an H2-receptor blocker, not significantly different in HIV observational database study. International Journal of STDs and AIDS 19(8): 561-562. August 2008. (Abstract).