Therapeutic Drug Monitoring: Medscape Web Resource Page.

Therapeutic drug monitoring (TDM) means measuring the level of a drug actually found in the blood (or inside certain blood cells), in order to adjust the drug dose up or down, either to make sure there is enough to inhibit HIV or to avoid side effects. The reason for measuring drug levels is that people are different, both in how well they absorb drugs from the stomach or intestines, and in how rapidly the body destroys or eliminates the drugs. For various reasons, there is most interest today in measuring blood levels of protease inhibitors.

For years there has been reluctance to measure HIV drug levels in routine patient care, because the current one-size-fits-all dosing is more convenient. Companies are racing to make their medicines easier to take (preferably a single pill once a day), and adjustable dosing would probably require more pills and/or increase the chances of error. Companies have incentive to sell their existing products -- not to bring attention to their variable blood levels or other complications.

TDM is not yet part of standard HIV care, but increasingly new information suggests that it may become important for helping antiretrovirals work better. In the future, it is likely that shortly after one has started taking a protease inhibitor (and perhaps other antiretrovirals as well), the blood level will be tested in order to adjust the dose if necessary.

Recently the Medscape HIV/AIDS Web site (http://hiv.medscape.com) added a page of links to recent articles, conference summaries, news reports, and other information about therapeutic drug monitoring in HIV treatment. This page will be updated as new information becomes available. Currently the link is under "Resource Centers" on the home page.

Note: You need to register in order to read the articles on the Medscape site, but registration is a one-time process and is free. You will need to make up a user name and a password, and write them down for when you use the site again; you will also be asked to complete a short survey. This site has much useful information and is worth the trouble of registering.