Some mutations can keep multiplying even when you are taking an antiviral drug. When this happens, the drug will stop working. If you take a protease inhibitor by itself, resistance develops within one month. When you take more than one antiviral drug at the same time, HIV mutates much more slowly and it takes much longer for resistance to develop. Sometimes, if you develop resistance to one drug, you will also have resistance to other antiviral drugs.
Resistance can develop quickly.
It is very important to take protease inhibitors according to instructions, on schedule, and not to skip or reduce doses. Ritonavir is taken by mouth as a liquid or capsule. The capsules are 100mg, so you will take 6 capsules every 12 hours. Ritonavir should be taken with meals, if possible. Ritonavir is sometimes combined with other protease inhibitors.