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Aim at 95% Adherence for Protease Inhibitors

Kathleen Bennett

Anything less than a 95 percent success rate at taking prescribed doses of protease inhibitors should be considered inadequate, clinicians at two HIV clinics suggest.

Of 81 HIV-infected adults who did not use a medication organizer, those who consumed at least 95 percent of the prescribed doses of a protease inhibitor for three to 15 months were significantly less likely than other patients to respond poorly, the clinicians reported in the July 4 issue of Annals of Internal Medicine. 

Virologic failure, determined from the number of copies of HIV nucleic acid in the blood, occurred in 22 percent of patients who took at least 95 percent of the doses, compared with 61 percent of patients who took 80 percent to 94.9 percent of the doses. Patients at the higher level of adherence spent fewer days in the hospital than did other patients and had no opportunistic infections. 

The researchers measured therapy adherence by using a microelectronic monitoring device attached to the drug container's cap. Each time a patient opened the container, presumably to take a dose of the protease inhibitor, the device recorded the date, time, and duration of opening. 

At the start of the study, each patient's primary HIV physician and clinic nurse predicted whether the patient would take at least 80 percent of the prescribed protease inhibitor doses. Physicians were wrong 41 percent of the time. The nurses did better, incorrectly predicting that level of adherence only 30 percent of the time. 

Given the importance of protease inhibitor therapy to virologic response in HIV-infected patients, the study's authors urge health care providers to aim for 95 percent—not the conventional 80 percent—as the minimum adherence rate. The authors also suggest that health care providers query patients more extensively than simply asking whether they missed taking any doses in the one or two days preceding the clinic visit. 

Click here to read the article (in PDF).