When is therapeutic drug monitoring (TDM) appropriate?

TDM is important when routine recommended dosing is not always appropriate.

For example:

  • In children.
  • In people with pre-existing liver or kidney damage.
  • When drug levels might be linked to side effects. If you get yellow eyes with atazanavir TDM can help find an effective lower dose.
  • When drug interactions are a concern. For example, when antacid drugs like omeprazole reduce levels of atazanavir and cause treatment to fail.

TDM involves taking a blood sample, usually after you have been on a treatment for at least two weeks.

The hospital needs to know the exact time that you took your previous dose in order to interpret the results.

Sometimes a sample is taken just before you are due to take your next dose, and sometimes it is also taken 2–3 hours afterwards.

TDM is part of an individualised approach for specific groups of people on ART.

More information on TDM
Lab 21 Commercial lab in the UK running TDM)

Last updated: 1 August 2016.