Specimen Collection Phlebotomy Procedures Drawing Drug Levels

Accurate and precise timing, both in administering the drug and obtaining each blood sample, are of the utmost importance in therapeutic drug monitoring. For meaningful interpretation, knowledge of the length of time that has elapsed since the last dose is imperative. During long-term therapy blood samples should be taken in the "steady-state", i.e., after treatment with a constant dose over at least 5 half-lives.

TROUGH

• Trough sample should be drawn 0-90 minutes (30 minutes optimal) before the dose.

PEAK:

1. Draw 30-90 minutes after the end of an IV administration.
2. Draw 60 minutes after IM injection.
3. Draw 1.5-6 hours after oral administration depending on the bioavailability of the drug.