When you don’t take enough anti-HIV medication, you may not achieve the full benefits that a drug can provide. For example, if you take a smaller dose than prescribed, miss a dose, or take a “drug holiday,” more virus copies may be produced, and the amount of virus in your body may start to increase.
In addition, the more copies of the virus that are made, the greater the possibility that the virus will become resistant to your medication.
To understand this, think of a production line making socks. For every 10 socks that are made on this production line, there is one mistake or “irregular” sock; for every 100 socks made, there will be 10 irregulars.
If many of the viruses in your body have these mutations, your medication may not work as well. This is called drug resistance.
If this happens when you are taking a protease inhibitor, other protease inhibitors may be less effective against the virus, too. This is called cross-resistance and it can also happen in other classes of anti-HIV medications.
Cross-resistance happens between one or more drugs in the same class (such as protease inhibitor to protease inhibitor) but usually not between drugs belonging to different classes of anti-HIV medications (such as protease inhibitor to reverse transcriptase inhibitor).
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If you do take all your medication, you’ll be able to help keep the virus from making so many copies. This can result in fewer mutations (”irregulars”), which may help prevent resistance, and may help keep your medication working longer.
If you don’t take all your medication as prescribed, there’s a greater chance that the amount of virus will increase and more mutations will be made. This may then lead to resistance and may keep your anti-HIV medication from working as well, or working at all.