About half of HIV patients on antiretroviral therapy skipped their medications whenever they were drinking alcohol, according to a U.S. study - an ill-advised behavior that researchers say could lead to higher viral loads.

The study, published in the Journal of General Internal Medicine, for a year followed nearly 200 people with HIV who were on antiretrovirals and drank alcohol. It found that 51 percent stopped taking their medications while drinking.

Lapses could be due to forgetfulness while under the influence, but a widespread - and erroneous - belief that mixing alcohol and HIV drugs can be toxic appears to play a role.

Drinking has been known to interfere with people's adherence to their medications, but researchers said the consequences of inconsistent use of HIV medications can be more severe.

Antiretroviral drugs suppress the HIV virus, and patients must take the medications continuously to prevent the virus from surging. Additionally, going on and off the drugs can lead to drug resistance.

At the beginning of the study, the researchers asked the participants about their alcohol-related beliefs, such as whether they thought their drugs wouldn't work as well if the two mixed. They also asked whether people would not take both at the same time, either by avoiding alcohol or the medicines.

Over the following year, the team checked in with patients every month to see how well they were sticking to their prescriptions through a pill count, and every other month they called to ask how often the patient had been drinking recently.

Doctors' offices measured each patient's level of virus and measures of immune system health.

They found that 51 percent of the patients would avoid the medications when they drank, and half of the people in this group had poor adherence to their prescriptions. In addition, half of the group that skipped pills said they wouldn't take them again until the alcohol was out of their system.

People who skipped medications while drinking were also more likely to have higher levels of HIV in their bodies and lower numbers of CD4 cells, a measure of immune system health.

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