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32 Cards in this Set

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Vancomycin trough

If the actual body weight is greater than 25% of the calculated IBW, calculate the adjusted body weight
IBW + 0.4(Total body weight - IBW)
When is it most appropriate to check drug plasma concentrations
steady state
How many half-lives does it take for a drug to be almost completely eliminated

equivalent to 6.25%-3.125% of drug remaining in the body. After 7 half lives <1%
What determines half-life
clearance (Cl) and volume of distribution (Vd)

half-life = 0.693Vd / Cl
What determines elimination constant
Cl and Vd

ke = Cltb / Vd
What SrCr values give a better estimate of renal function for elderly with low SrCr (<0.8mL/ming)?
When is a trough taken?
30 mins before next dose

Ideally this trough would be equal to Cpmin. If trough is drawn earlier than right before the next dose:

Cpmin = observed Cp trough x e^(Ke*time)
When is a peak taken?
30 mins after a 30-min infusion

Cpmax = measured Cp peak / e^(Ke*time)

where time is the difference between the time of the end of infusion and the time of the measured Cp
Antibaterial activity of aminoglycosides: time or concentration dependent killing?

Optimal batericidal activity is achieved when peak concentration is about 10 times MIC

Higher peak = better clinical outcome

- varies with organism and concentration
- greater for gram neg. than gram pos.
- increases with increasing aminoglycoside peak concentrations
prominent postantibiotic effect
gram positive
serious infections e.g. endocarditis, sepsis
population Vd and t1/2 for gentamycin and tobramycin
Vd ~ 0.3L/kg (will be higher in pregnant, critically ill, ascites, CHF pts)
t1/2 ~ 2h
When is it beneficial to give LDEI
less toxic, less monitoring, less costly. also easier to convert to home IV therapy

Large dose extended interval dosing allows kidneys to recover from nephrotoxic effects of AGs. Efficacy will not be compromised because of PAE.
Who is eligible for LDEI
good renal function.

AVOID in pts with altered Vd, pregnant, critically ill, quadriplegics, ascites, CF, renal dysfunction CrCl <20mL/min, ESRD on hemodialysis or CAPD
Gentamycin/tobramycin Cp max and Cp min
Cpmax = 15-20mcg/mL
Cp min <1mcg/mL or undetectable

gentamicin MIC for pseudomonas aeruginosa is usually ~ 2mcg/mL, so desired Cmax is about 20mcg/mL.
Gentamycin/tobramycin drug-free period
Optimally, 4 hours <0.5mcg/mL
gentamicin/tobramycin empiric dosing
gram neg: 5-7mg/kg/dose
gram pos: 3mg/kg/dose

CrCl>60: Q24h
>40: Q36h
>20: Q48h
gentamicin/tobramycin monitoring
Peak: random level 8-12 after 1st dose. 30 mins after second 30-minute infusion

Trough: 24h after 1st dose. continue regimen if <1mcg/mL
gentamicin/tobramycin target concentrations (with conventional dosing)
synergy for gram pos: 3-4mcg/mL
gram neg: 6-8mcg/mL (UTIs, bacterimia, pneumonia, sepsis)
cystic fibrosis: 8-12mcg/mL

Cpmin: <1-2mcg/mL
gentamicin/tobramycin empiric therapy
Loading IV bolus dose: 2mg/kg i.e. desired plasma conc x Vd

Interval: (lnCpmax - lnCpmin) / ke...which is 0.0293*CrCl+0.01...+ infusion time in hr.
Interval is usually ~ 3 t1/2s

Maintainence: they are A-holes if they want you to calculate this without a log-function calculator. So the answer is A.
gentamicin/tobramycin monitoring
infection s&S
peaks especially if aggressive targets are used (peak of 8mcg/mL or trough of 2mcg/mL)

gentamicin/tobramycin steady state
4 SrCrs is about one half-life. So steady state is about 4*SrCr *4 = 16*SrCr.
blue syndrome
3A4 inhibitors
check thyroid function
blocks Na
can use in CVdz
only for maintainence
quickest onset, dose based on CrCl and QTc

blocks K+ from reentering
AVOID using with HCTZ
1st afib <48h
IV, most stay in hosp>3d for obs
QTc prolongating drugs

(>440 msec)
quinidine (also causes D)
procainamide (also causes lupu)