Drug resistance

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18 Dec 2014

James from Newcastle, NSW writes: Is it true that after a number of years most people develop resistance to HIV treatments? I have just started taking antiretrovirals and wonder what I can do to stop my virus becoming resistant.

Dr Louise replies: Thank you, James. Firstly, let me just recap what ‘resistance’ means.

HIV is capable of replicating at great rates and sometimes the replicated virus is not exactly the same as the parent virus . These changes may be insignificant or they may affect the characteristics of that virus .Sometimes they can even make the virus resistant to some antiretrovirals so that even in the presence of the medication, the virus is able to continue to replicate. This is more likely to happen when you don’t take your antiretrovirals correctly or miss doses.

We know that adherence to medication is one of the most important determinants of treatment outcomes. High levels of adherence suppress HIV replication and lessen the probability of drug-resistant mutations evolving. Resistance can occur when there is inconsistent exposure of the virus to the drug. The drugs will have some effect on the virus , but not enough to completely inhibit viral replication. This can then lead to the development of resistance and less susceptibility to the drugs.

Current treatment regimens usually include at least three drugs from two different classes. This way we can maximise the chance of totally suppressing viral reproduction as well as help CD4 cell recovery and function.

These days we are able to test someone’s virus for any drug resistance before they start treatment so we can tailor the regimen to suit the person and the virus .In some cases, people may have a drug-resistant virus without ever having been exposed to HIV treatment. This is called ‘transmitted resistance’.

Once people commence treatment, we monitor their CD4 count recovery and their viral load. If these improvements are not as good as we hoped, then we look at factors that could be contributing to that.

Adherence is something that your doctor is likely to ask you about quite often. Before starting meds it is good to discuss strategies that may help you to take your pills on time all the time. Pharmacists, nurses and support workers can also offer advice. Some people load up a dosette box for the week or have alarms on their mobile phones and keep a spare dose stored away just in case.

In the past, people took ‘drug holidays’ – stopping medications for weeks, months or even years. We now know this can have serious ramifications and is not recommended.

If you are having trouble with your regimen, get back to your doctor and talk about it. If it is related to side-effects, your doctor may have a simple answer or may recommend a change of regimen.