Resistance

I have had some people ask me some questions about drug resistance, and other issues that are related. So, let me do my best to explain it a bit better. I've been meaning to write this post for awhile...

"Resistance" in HIV talk refers to the reduction in effectiveness of ARV medications in fighting the virus within a person's body. When the virus is able to mutate, it then develops resistance to a medication or group of medications. When the virus is resistant to the medication, the medication stops working to control the virus. This leads to treatment failure, and the need to switch to new medications. Resistance can happen in a variety of ways (this may not be an exhaustive list):

• Poor treatment adherence: taking medications at the wrong time or in the wrong way, skipping doses, etc. (This is much similar to when a person is on any antibiotics or other medications... when a person skips doses or doesn't take them at the correct time each day, the level of medication within their system decreases, and therefore allows the illness to mutate and the medication to lose its effectiveness)
• Being infected with a resistant strain of HIV: this means someone passes their resistance to you (this can happen the first time a person is infected with HIV or happen to an already HIV+ person who is reinfected with a different strain of the virus). 
• Drugs, alcohol, smoking, diarrhea, or other medications: these all can interact with HIV medications and decrease the absorption level or level of medicine in the body

All HIV+ people are usually "Resistance Tested" prior to starting treatment. This resistance testing will tell the doctors whether a person's specific strain of HIV is resistant to certain medications or combinations of medications. This helps the doctors and patient to choose the best treatment option. Once a person is resistant to a certain medication, it is likely that that medication will never work or be able to be used for that patient again. Some people (through the factors listed above) may continue to build up resistance to many different medications during their life, and must keep "going down the list" to a new/different medication option. We are lucky that there are MANY MANY different types of HIV medications, but resistance is still a very dangerous thing.

Now a friend asked me a question, "So is it safe for you to have unprotected sex with another HIV+ person, since you both have HIV?". The answer is "NO", and let me elaborate a little more on why...

Let's say that "John" has had HIV for 10 years. During that time he has had very poor adherence. He often forgets to take his medicine or takes it many hours later than he should. He also tends to drink and smoke a lot. Due to some of these activities, John has already developed resistance to 3 different HIV medications.

Now, John meets "Sue", who is HIV negative. John and Sue have unprotected sex, and Sue become HIV+. When Sue goes to her first doctor's appointment to discuss treatment options, they do resistance testing on her. The resistance test shows that Sue's strain of HIV is resistant to 3 medications (the same 3 that John is resistant to). Unfortunately, Sue has not only been infected with HIV, but John's resistance has also passed on to her. Because of this, Sue (from day one) will never be able to use those 3 medications.

Now, John meets me (Jessica). I have had HIV for 6 months, and I am taking a medication called Atripla. My strain of HIV is not currently resistant to any medications. I can take any and all of them, and they should work. John and I decide to have unprotected sex, because we figure we both already have HIV, what should we have to worry about? Unfortunately, there is a chance that I can, in essence, be "reinfected" with John's strain of HIV, and along with it his resistance. I could suddenly go from having no resistance, to being resistant to 3 medications. Furthermore, IF one of the 3 drugs John is resistant to is in Atripla (my medication), my medication may stop working, and I may have to switch to a new medicine.

As you can see, drug resistance is a big deal, and a very dangerous thing, both for people with HIV and for people without...

Addition 3/7/2012: 
My sister asked yesterday after reading this post, "Can resistance eventually happen to a person even when they do everything right (i.e. proper adherence, etc.)?" I answered her at first with "As far as I know, No, it shouldn't. If a person always takes their medication as prescribed, and no other of the above mentioned situations lead to resistance, then a person should be able to stay on one medication and have it continue working. I do not believe that resistance can naturally build up over time."

However... I just did a bit more research into it... and it seems that I was wrong... because HIV is always mutating, there are always variant forms of HIV being created in your body (even though they are small lesser amounts than the wild type virus)... but, because of these natural mutations, it is possible that resistance may at some point develop even if someone is doing everything right. You can read more of the scientific explanation on this website. Also, here are some good tips about preventing resistance from developing:

•  Learn all you can about anti-HIV drugs. The more you know, the easier it will be to make treatment choices that help you avoid drug resistance. Reading the information on this web site about anti-HIV medicine is a good first step.
•  Start treatment with a powerful anti-HIV regimen. Your first shot at anti-HIV treatment is probably your best chance at fully suppressing the virus and preventing the development of drug resistance. 
•  Be sure to follow instructions. It is very important that HIV-positive people take their anti-HIV medication exactly as prescribed. Missing doses, not taking the right number of pills, or eating when pills need to be taken on an empty stomach, can all cause viral load to increase and cause drug-resistance mutations to develop.
•  Communicate with your doctor. Knowing how to take your medicine properly and reporting any problems to your doctor are important for avoiding drug resistance.
•  Monitor the effects of your drugs frequently just after you begin, and regularly throughout your treatment. Often an increasing viral load is the first sign that drug resistance is developing. Also, there are reports of people being infected with drug-resistant HIV. Monitoring viral load is a good way to guard against drug resistance. 

One other note that I forgot to mention in my post yesterday is that it is easier to develop resistance to some HIV medications than others. For example, I am on Atripla, which is one of the #1 most recommended treatments, but it also happens to be one of the easiest to develop resistance to (if not taken properly).