March 15, 2001
Sequencing -- sequencing is usually used to describe the order a person might choose anti-HIV medicines. For example, I may choose to take a regimen including Viracept and then a regimen including Kaletra. If I am sequencing these drugs, I am choosing to take them in a specific order. We also use the term strategizing for this process.
Tolerability -- refers to how tolerable the side effects of a medication are. For example, if something gives you chronic diarrhea, it may have low tolerability (hard to live with). However, something that only gives you an occasional headache might have good or high tolerability.
Efficacy -- how effective or potent a medication is in doing its job. When we study new drugs in clinical trials, one of the things we are trying to learn is about the efficacy or effectiveness of the drug.
Toxicity -- we frequently use the terms side effects and toxicity together. For example, if a drug causes liver toxicity, then it puts a strain on the liver and makes it more difficult to do its job. The blood work you have with your CD4 cell count usually measures these changes in normal functioning or toxicity.
Resistance -- when a drug becomes less effective against HIV, we say that HIV has become resistant to the drug (usually caused by mutations or changes in HIV's genetic material).
Cross-Resistance -- when the resistance to one drug also causes resistance to other drugs because of similar "weak spots" among the drugs.
Hypersensitivity -- when someone reacts to a drug with an exaggerated reaction. For example, Ziagen can cause a severe hypersensitivity reaction that can be fatal if the drug is continued or re-started.
Pharmacokinetics (PK) -- how the body absorbs, processes, and gets rid of a drug. Pharmacokinetics is important because it helps us understand how much drug someone needs to take, how often they need to take it, and what the possible side effects or drug interactions could be.
PK Boosting -- we use this term to describe ways in which we can increase absorption or the length of time a drug stays in the body. PK boosting is an important concept in HIV because we use it to decrease pill counts, remove food restrictions, and make taking HIV medicines easier by combining medications that boost each other.
Structured Treatment Interruption (STI) -- a defined break in taking anti-HIV medicines. It is different from drug holidays and from discontinuing treatment because STIs should be a set amount of time that someone will stop medicines and then re-start. It is done to try to jump-start the immune system. STI strategies are being researched now, but have not been proven effective.
Co-Formulation -- a combination of two or more drugs in one delivery system (like a pill, a liquid, or even an injection). For example, the new protease inhibitor drug Kaletra is actually a co-formulation of two drugs (Norvir and lopinavir) combined in one pill.
Dawn Averitt is the founding director of WISE and a national AIDS treatment advocate and educator.