How do I choose the strongest combination?

If your current treatment is already your second, third or later combination, and you decide to change treatment, then choose the strongest combination you can for the next treatment.

Use as many new drugs as possible that are not cross-resistant to previous drugs.

The most impressive results from recent trails have been where people have used at least two and ideally three new sensitive drugs. See Figures 9 and 10 below.

Ask for results from trials of people in your situation. Although all drugs have been tested both on their own and in different combinations, there will not always be studies that match your exact treatment history.

Check whether drug interactions are likely in more unusual combinations.

One measure of the potency is how far a drug causes viral load to fall. This is usually measured in ‘logs’. A log 10 is a multiple of x10. See Table 1 below.

Table 1: Log scales (a log 10 scale is a multiple of a factor of 10).

A drop from 50,000 down to 50 is a drop of three logs. The greater the log drop, the more potent the combination.

Another way of looking at results is to ask about the percentage of people taking the drug whose viral load went below 50 copies/mL. The closer this is to 100% the more potent the drug and the more likely it will work.

You cannot compare results from different studies without considering the health of people in the study. If everyone started with a very low viral load or a high CD4 count then it would be easier to show good results.

Look at how long the trial lasted and how long people were followed. If the results continued for over a year it will give you more confidence.

Impressive short-term results may just mean it is a combination that is easy to tolerate or adhere to. But is could also mean that good drugs were not supported by other active drugs.

Monitor your new treatment carefully. Aim for a viral load test 2–4 weeks after a treatment change. Then have regular viral load tests every 1–2 months.

If you have problems with adherence or side effects, discuss these with your doctor.

Using a new drug in a combination without other active drugs will not be strong enough to get viral load to less than 50 copies/mL. It may reduce viral load by 1-2 logs each time, but the benefit will only be short term and viral load will rebound with resistant virus.

This strategy is only worth considering if your CD4 count is very low (less than 50 cells/mm3) or if you have other serious symptoms.

Waiting until you can use at least 2–3 new drugs together at the same time will make the new combination stronger. It will then perhaps be able to reduce viral load by 3 logs to less than 50 copies/mL.

Even though your viral load may continue rising before you switch, if you wait until you can use at least two or more sensitive drugs, that combination is more likely to get your viral load below 50 copies/mL.

This makes the likelihood of developing resistance much lower. Treatment can then work for much longer – hopefully for years.

Figure 9: Using only one active drug will only work for a short time

Using only one active drug will only reduce each viral load drops by 1-2 logs, and not to less than 50 copies/mL.

If a new drug is not supported by other active drugs, resistance will develop.

Figure 10: Waiting to use three new drugs is more likely to get viral load undetectable

Waiting until you can use two or three new drugs together will make the new combination stronger.

Viral load can now drop by over 3 logs.

If viral load gets to below 50 it is likely to stay there without rebounding or developing further resistance.