March 7th 2011

The goal of HIV treatment is to reduce the amount of HIV in your blood to ‘undetectable’, thus enabling your CD4 count to increase and your immune system to return to optimal function. An undetectable result does not necessarily mean that there is no HIV in your blood, or other parts of your body, rather the test used cannot detect (find) any HIV in your blood.

Most tests used in pathology labs have a ‘sensitivity’ or ability to detect HIV at 40 or 50 ‘copies’  per ml or drop of blood.  This means such tests cannot detect HIV below these levels, so someone with an undetectable result could still have active HIV in their blood below these levels.  In recent years, new and more highly sensitive HIV viral load tests have been developed that can detect a viral load below one copy/ml. Although being undetectable at less than 1copy/ml could be considered to be zero in plasma, or the liquid part of blood, HIV can still ‘hide out’ in parts of the body called reservoirs.  Examples of these reservoirs include the brain, gut and lymph nodes.

A team of French investigators has found that people who are taking an HIV treatment combination that includes nevirapine (Viramune) are more likely to achieve a viral load of zero than people taking a combination that includes efavirenz (Sustiva, also in the combination pill Atripla).

The researchers designed a retrospective study involving 75 patients treated with nevirapine and 90 individuals taking efavirenz-based combinations who had an undetectable viral load below 50 copies per ml of blood for at least six months using a test capable of detecting virus below one copy/ml.  The results showed that 81% of people taking nevirapine had a viral load of zero compared to 56% of individuals treated with efavirenz.

Previous research has suggested that treatment combinations that include a drug from the NNRTI (non-nucleoside reverse transcriptase inhibitor) group of HIV drugs are more likely to suppress viral load to extremely low levels than treatment based on a protease inhibitor (PI), a different class of drug.

There is also some evidence that nevirapine is more effective at reducing viral load to lower levels than efavirenz. The investigators believe that research demonstrates “the stronger ability of nevirapine than efavirenz to better control residual (HIV), in patients with (undetectable viral load).” They suggest that this is because nevirapine is better able to penetrate “reservoirs”, or places in the body that HIV can ‘hide’ and treatments are unable to get to.

“The clinical relevance of having a viral load below 1 copy/ml has yet to be shown,” conclude the researchers, who call for studies “to explore, for example, the relationship between the level of (HIV) and systemic inflammatory or immune activation markers .”

It’s currently unclear what the benefits are of having a viral load of zero. However, it’s known that even low levels of HIV can cause inflammation  and that this can increase the risk of some serious illnesses, for example cardiovascular disease and some cancers. Therefore including nevirapine in your combination could in theory reduce the risk of developing these health issues.  It is also theorised that the lower someone’s viral load the less chance they have of passing on HIV during unprotected sex, in the absence of another STI or lesion (cut or sore) to the genitals.

So . . .  is Nevirapine for me?

For people starting treatment for the first time with a combination that includes nevirapine there is a risk of liver toxicity depending on your CD4 count.  The risk is different for men and women.  Men with a CD4 count above 400 per ml, and women with CD4s above 250 per ml, are at higher risk of experiencing liver related side effects if starting nevirapine.

However people who have been taking other HIV treatments, have an undectable viral load and do not have resistance to nevirapine can switch to nevirapine quite safely.  If you think you would benefit from taking nevirapine, or would like to include it into your combination, you should discuss your options with your HIV doctor.

Download the full study (PDF): Higher efficacy of nevirapine than efavirenz to achieve HIV-1 plasma viral load below 1