Before discussing drug interactions, it may be useful to review some basic pharmacological terms, abbreviations, and processes.

AUC is 'area under the curve'. To understand AUC, picture a graph where the y axis represents plasma drug concentration and the x axis is time. You would start to draw a line when a drug is taken. It would curve upwards and at the time of Cmax, the line is at its highest point. As the drug concentration lessens, the line drifts downward until Cmin is reached. The area where the drug is at a therapeutic concentration in the bloodstream is the 'area under the curve'.

Bioavailability is a measure of how much of an administered drug is absorbed into the bloodstream and actually reaches its intended site of action in the body. If a medication is designed to be taken on an empty stomach, taking it with food changes the drug's absorption rate and subsequent bioavailability. An example of this is seen with grapefruit juice. Grapefruit juice inhibits the enzymes that break down certain medications; this can increase their bioavailability to sometimes toxic levels. If a drug is not broken down by the same enzymes that break down grapefruit juice, then there will not be a variation in bioavailability. In most cases, a drug is active only until it is broken down, at which point it usually leaves the body.

Cmax is the maximum concentration of drug in the bloodstream. This usually occurs just after taking a drug and is also known as 'peak concentration'.

Cmin is the minimum concentration of a drug in the bloodstream. Usually by the time Cmin has been reached, it is time for another drug dose. Cmin is also known as the 'trough concentration'.

Half-life is the amount of time it takes for drug concentration in the body to fall by half.

IC refers to inhibitory concentration. This term comes from the laboratory. When studying the action of a drug in a test tube ('in vitro' meaning 'in glass'), researchers see how much drug is needed to slow down HIV production. When viral production is reduced by half, it has reached a level called IC50. Ideally, a drug would have an IC100. However, by the time a drug reached that level, the amount of drug in the bloodstream would probably be toxic.

Metabolism describes the biochemical processes taking place within cells that allow them to live, grow, and divide. Anabolism uses energy to build complex cell components from substances with a simple constitution; catabolism breaks down or transforms substances to produce energy. Some nutrients bind with drug ingredients, reducing their absorption or speeding elimination. Genetics can also affect metabolic processes.

P450 is an enzyme path used in the liver to break down many drugs.

PK stands for pharmacokinetics and generally refers to how drug levels in the body change over time.

Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.