How to TDM?

[xiongliang0]

therapeutic drug monitoring

such as amikacin, gentamicin ....

[JonF]

what about it?

[xiongliang0]

what about it?

Thanks for JonF's reply.

For example. Piperacillin/tazobactam has an MIC of 16ug/ml for Gram-negative organisms, other than P. aeruginosa, while 8 µg/ml for Staphylococci and 64ug/ml for P. aeruginosa.

For the best efficiency of the antibiotics, the MIC mast be acchieved during the therapeutic duration.

And the TDM is a way to make sure the antibiotics level in the blood upper than the MIC I think.

Follows are the basic data about Piperacillin/tazobactam from San Francisco VA Medical Center's Antibiotics Guidlines 2007:
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The elimination half-life of piperacillin/tazobactam is 0.8-0.9 hour. The drug's clearance is reduced and half-life is prolonged in renally impaired patients; therefore dosage adjustment is necessary. Peak plasma concentrations following a 30-minute infusion of piperacillin/tazobactam 4/0.5 gm are 277/34 µg/ml.
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But as a Pharmacist Specialist, he should know how to adjust the dose or the fequency of the admission and he also is able to explain why this adjustment is useful to Doctors, Nurses and the patients.

And the level of the antibiotics must be lower than the toxicity level to avoid the ADR.Especially the Gentamicin needs TDM.(AS we know the nephrotoxicity and Ototoxicity of Gentamicin is not allowed to happen)

Follows are the basic date about Gentamicin from San Francisco VA Medical Center's Antibiotics Guidlines 2007.
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Traditional dosing
Therapeutic peak and trough gentamicin or tobramycin serum levels are 4-8 µg/ml and 1-2 µg/ml, respectively. In order to obtain the most useful information, serum levels of aminoglycosides should be drawn after the third or fourth dose. Peak serum levels of aminoglycosides should be drawn 30 minutes after the end of infusion, while trough levels should be drawn immediately before the next maintenance dose. The following nomograms may be used to calculate initial loading and maintenance doses for patients receiving gentamicin or tobramycin. The nomograms should not be used in hemodialysis patients, obese patients, or patients with significant third-spacing. Serum levels should be used to make further dosage adjustments.

Once-Daily Dosing
Dose-dependent bacterial killing and a relatively long postantibiotic effect against most gram negative rods make once-daily aminoglycoside dosing a viable alternative to traditional aminoglycoside dosing. Most studies have shown similar efficacy with similar to less nephrotoxicity as compared to traditional aminoglycoside therapy. The recommended once-daily dose is 5 mg/kg based on ideal body weight. Obese patients (≥20% over IBW) should be dosed using obese dosing weight [IBW + 0.4(actual body weight-IBW)].
Once-daily, 5 mg/kg dosing should not be used for patients with an estimated creatinine clearance < 60 ml/min, treatment of endocarditis, or synergy against gram positive organisms. A serum trough level should be obtained prior to the second dose and should be undetectable. Peak levels are generally not recommended.

Gentamicin has a MIC of 4ug/ml
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But how to do and how to explain? I wonder.

In many patient with renal impairment it was said that redose according to serum levels (Consult ID pharmacy)

So I wonder how to do that?