Pharmacokinetics/Pharmacodynamics
Drug
Timing of Blood Sample
Therapeutic Rangea
Unbound Therapeutic Range
Amikacin
Peak (extended interval)
Trough (extended interval)
Peak (traditional)
Trough (traditional)
30–40 mg/L
undetectable
20–30 mg/L
< 8 mg/L
—
Carbamazepine
Trough
4–12 mg/L
0.5–4 mcg/mL
Cyclosporine
Trough
50–500 mcg/L
—
Digoxin
Trough (8–24 hr postdose)
0.6–2 mcg/L
0.4–0.9 ng/mL
Gentamicin
Peak (extended interval)
Trough (extended interval)
Peak (traditional)
Trough (traditional)
5–20 mg/L
undetectable
8–10 mg/L
< 2 mg/L
—
Lidocaine
Peak
1.5–5 mg/L
—
Phenobarbital
Trough
10–40 mg/L
—
Phenytoin
Trough
10–20 mg/L
1–2.5 mcg/mL
Tobramycin
Peak (extended interval)
Trough (extended interval)
Peak (traditional)
Trough (traditional)
5–20 mg/L
undetectable
8–10 mg/L
< 2 mg/L
—
Valproate
Trough
50–100 mcg/mL
5v15 mcg/mLb
Vancomycin
Peak and Trough to calculate
AUC
AUC 400–600 mg ×
hour/L
—
aTherapeutic ranges for antibiotics may be modified on the basis of pharmacodynamic target attainments (e.g., peak to MIC ratio).
bOptimal range for unbound valproate remains undetermined.
TDM = therapeutic drug monitoring.
Data adapted from: J Antimicrob Chemother 2016;71:2754-9; Clin Infect Dis 2020:71;1361-4; Ther Drug Monit 2017;39:522-30; Infect Dis 2023;10:ofad058;
concentrations can be measured when the drug is at steady state. The patient’s specific PK can be
determined and used to tailor the drug-dosing regimen. The following PK equations can be used to
calculate the various kinetic variables.
Determination of the elimination rate constant:
ke =
ln
Δ in time
C1
C2
where ke is the elimination rate constant, C1 is the measured peak concentration, C2 is the measured
trough concentration, and Δ in time is the elapsed time from C1 to C2 in hours.
Determination of the drug half-life:
t1/2 = 0.693
ke
where t1/2 is the calculated half-life.