Do some drugs develop resistance more easily?

From the i-Base guide to changing treatment (2015)

Figure 4: How one mutation can stop some drugs working

Graph showing how one mutation stops some drugs working

Some drugs stop working after only one mutation.

These include NNRTIs (nevirapine, efavirenz, rilpivirine and etravirine), integrase inhibitors (raltegravir) and some nukes (3TC  and FTC).

Figure 5: Resistance increases slowly with some drugs

Graph showing number of mutations increasing from 1 (low resistance) to 6(extensive resistance)

With some other drugs, the first one or two mutations make little difference.

If you continue taking the same drug, more mutations will develop that eventually stop the drugs working. These include most PIs and some nukes.