Is there a general rule when to draw a drug serum sample at trough, or does it always depend on the drug peak?

Antibiotics: For IV drugs, is it correct to draw a sample 30-60 minutes post administraton... but this kind of rule doesn't apply to PO drugs since they vary in peak?

2 Answers

  • 1 decade ago
    Favorite Answer

    You want to draw a trough right before the next dose. However if a trough is drawn early, you can forward extrapolate to find the correct blood levels. Drawing a peak is different. You must wait for the drug to distribute. For example, aminoglycosides are done with a 30 minute infusion time with a 30 minute wait time to draw peak levels or a one hour infusion then immediately draw levels. If levels are drawn late, you can back extrapolate to calculate the proper peak.

  • 1 decade ago

    The trough is like you said, 30-60 mins before next dose because thats the same with any drug. This has been choosen because it gives a time when a known value has been established for each drug. Same with the peak. I hope I haven't confused you even more.

    Source(s): Lab Tech for 10 yrs.
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