Guides

When to use new drugs and when to wait?

Any new combination should use at least two, and preferably three, active drugs.

But, using new drugs without other meds that are active will only give a short-term benefit. Viral load is likely to rebound again with more resistance. See Figure 9.

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

Graph showing viral load increasing overall from just below 50c/mL to over 5,000c/mL, with logs drops (1-2) not lowering viral load sufficiently.

Only one active drug is unlikely to get viral load to less than 50 copies/mL. 

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

It is only worth using one new drug 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 is usually a better strategy.

It will make the new combination stronger. It will then perhaps be able to reduce viral load to undetectable, when the benefit will be long term. See Figure 10.

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

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

Waiting to use two or three new drugs together will make the new combination stronger. Viral load can now get to less than 50 copies/mL.

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

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

1 log = 10 1.5 log = 30 1.7 log = 50
2 log = 100 2.5 log = 300 2.7 log = 500
3 log = 1,000 3.5 log = 3,000 3.7 log = 5,000
4 log = 10,000 4.5 log = 30,000 4.7 log = 50,000

Last updated: 1 January 2018.