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pharmacy ARV drug pick up
Jul 10, 2007

Its difficult to measure drug default from serum testing can I possibly use the pharmacy drug pick up default? any studies done on drug pick up as follow up on ARV therapy?

Response from Dr. Sherer

You are right, it is difficult to measure drug default, i.e. poor adherence, with drug levels in the blood. Although this measure will provide information as to whether ANY drug has been taken recently, it may provide rather poor information about recent medication adherence. This is particularly true for those medications, like the NNRTIs nevirapine and efavirenz, and FTC (emtricitabine) and TDF (tenofovir) that have longer half lives in the plasma.

And yes, several groups have used pick ups from the pharmacy as a surrogate for adherence with some success, in particular the British Columbia Center for Excellence led by Julio Montaner. It is important to understand the limitations of this method, i.e. just because someone has picked up their medications from the pharmacy does NOT mean that they take their medications regularly or on time. However, those patients who fail to fill their medications are highly likely to have poorer adherence than those who get their prescriptions filled.

The gold standard for measuring adherence is the simple self-report of the patient...and it is far from a perfect measure. Available evidence suggests that you can get good recall from patients with a high degree of reliability for pill taking behaviors over the past three days, so my practice is to note ALL doses taken over the past three days, as well as the answer to the question "Since our last visit, how many doses would you estimate that you missed (or were late)?" Over time this gives me and the patient a clear idea of ongoing adherence.

Another measure used commonly in clinical trials is the MEMSCAPS high tech medication bottle that keeps a record of every time the bottle is opened, presumably for each medication dose. As you can see, this also has some flaws, as patients could easily remove more than a single dose with the cap open, or they could open the bottle without taking a dose. Still, it is a useful measure, and most commonly corroborates reliable self-report data.

For more information about adherence in a succinct form, I refer you to the HHS Guidelines, which are available at

The bottom line here is that there is no perfect measure of adherence, but individual self-report is the simplest, and people on ART should be in the habit of reliably reporting their adherence to their doctors at each visit, with specific information about the three days before the visit, and as exact an account as possible of each missed dose, so the person and their doctor can devise strategies in future to prevent missed doses.

And this attention to adherence is critical, because poor adherence and lapses in adherence are the most common causes of treatment failure and drug resistance.

HIV Drug Resistance

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