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Imperfect HIV Drug Use Raises Resistance Risk

Failure to Take Medications as Directed Could Quadruple Drug Resistance Risk

HIV Drug Adherence Predicts Resistance continued...

The two biggest factors associated with drug resistance were inconsistent medication use and a high HIV level in the blood at the start of the study, which is the result of starting treatment later in the course of the disease.

Researchers found that HIV patients who took 80% of their medications were four times more likely to develop drug resistance than those who rarely picked up their HAART prescriptions.

"If you don't pick up any of your prescriptions, you're not very likely to pick up drug resistance," says Harrigan. "But that's not where you want to be in terms of your health because patients with lower adherence had a lower likelihood of actually surviving."

The study showed that the risk of developing drug resistance was highest among people who took their drugs as prescribed 70%-90% of the time.

Those who were near perfect in refilling their prescriptions (greater than 95% refill rate) and actually took them as directed according to blood tests had a fourfold lower risk of developing drug resistance compared to inconsistent HAART users.

Researchers say this group likely avoided drug resistance by effectively suppressing HIV to nearly undetectable levels, which dramatically reduces the risk of the virus mutating and becoming resistant to medication.

However, only about 30% of the HIV patients in the study fit into this "near-perfect drug user" category, and researchers point out that this is among a group of Canadian citizens who received their medications and health care free of charge.

Helping HIV Patients Take Their Medications

In the U.S., researchers say nearly 50% of HIV patients have detectible levels of the virus in their blood, an indicator that they may not be taking their HAART medications as prescribed.

Experts say failure to take HAART as prescribed is a major factor behind treatment failure and progression to AIDS. Although nonadherence is a common problem in many diseases, researchers say the issue is particularly dangerous in HIV treatment.

"Nonadherence is nonforgiving with HIV infection," says John G. Bartlett, MD, chief of the division of infectious disease at the Johns Hopkins University School of Medicine in Baltimore, Md. "If you don't take your blood pressure medication, your blood pressure goes up for that day and then goes back down again. But with HIV medication, you don't get the chance of them being active or effective later."

The antiretroviral drugs used in HAART work by preventing the virus from replicating. But when a dose of the drugs is missed, the levels of the virus in the blood can rise rapidly and begin to mutate, which increases the likelihood of resistance.

One of the reasons it has consistently been difficult for HIV patients to take their medications as prescribed is that the treatment regimen often required taking as many as 14 pills at different times or with different food restrictions.

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