Trough Level Axb

nurseprnRN, BSN, RN · Mar 4, 2012

peak and trough level of an antibiotic are the highest and lowest drug level in the patient's blood. if you think about it, you will see that the drug level will be highest right after a dose is given. the level then decreases over time. if you know how low it can go before it loses effectiveness, that helps you figure out how much should be given and how often so the level is never that low.

peak levels are drawn right after the dose is given. trough levels are drawn just before the next scheduled dose. that way, the trough level tells you whether the blood level of the drug is too low or if it is still in the therapeutic range.

if a dose is missed, not given on time, the level will continue to decrease; if you draw a trough then, it will be lower than it would have been if it had been drawn sooner, on time before the scheduled dose. this result would not give useful information. the delay in the dose means the patient is not being adequately treated for his infection.

none of this has anything to do with pharmaceutical manufacturers or pharmacists, although pharmacists are really good people to ask questions like this because they often know what the therapeutic drug levels are.

melissacarey · Mar 4, 2012

So the trough levels are different for each drug?

What is the average trough level where we would give another dose, or hold back. Thanks!

rita359 · Mar 4, 2012

Various abts have peak and trough levels drawn or just trough levels. There are no averages. Levels are specific to the drug. Keeps pts from getting toxic reactions to the specific drug. Examples might be damage to the nerve to the ear causing hearing loss or damage to the kidney causing renal failure. Drugs have to be given at specific times so levels don't go to high causing toxic reactions. Levels have to be drawn at specific times so they are correct. Same thing for infusion times on these drugs. Lower doses can be given in 1 hr. Higher doses are given over longer periods of time specific to your facility policy and procedure.

melissacarey · Mar 4, 2012

Ok, I understand. thanks!

psu_213, BSN, RN · Mar 4, 2012

I don't know if this is true at all hospitals, but at one place I worked the physicans could do a 'pharmacy consult' for ABX where peaks and troughs were monitored (such as vanco). Here the pharmacist would monitor the levels and give dosage for the next dose of the medication. Drug companies had nothing to do with it.

netglow, ASN, RN · Mar 4, 2012

Say you have a patient that is septic and beginning to approach that drain.

Your gut tells you to do what?

Slam him with antibiotics to gain an edge over the infection in his body because this is an emergency.

What can happen if you slam someone with abx?

You very well might kill him with those antibiotics.

What can happen if you are sketchy with your dosing/choice of abx because you are afraid you might kill the guy?

The infection will kill the guy.

What can you do?

You can choose your abx by specificity testing (what kills the pathogen in the lab) Then use those abxs. You can dose the patient and draw peak and trou. This way you can do an "educated slam" and get as much abx as you can into the patient to try and gain control over the bacteria. If you don't keep the level of abx consistent, the bacteria will probably "over-rule" your attempts to save your patient. All along you are testing body systems for signs of failure/shock. Remember this kind of heavy dosing is not kind to the body, and, that antibiotics don't always save the day.

sapphire18 · Mar 5, 2012

At our hospital also, certain abx dosing is managed by pharmacy based on peaks and troughs. Sometimes they also adjust the inital dosing based on pt's weight and kidney function.