Vancomycin is a widely used glycopeptide antibiotic that requires therapeutic drug monitoring (TDM) owing to its narrow therapeutic window. It is primarily eliminated by renal excretion; thus, estimating the renal function of a patient is vital in the TDM of vancomycin. In patients with Duchenne muscular dystrophy (DMD), it is difficult to estimate the glomerular filtration rate using the serum creatinine level owing to the pathophysiological nature of the disease. Here, we report a case of a patient in whom TDM of vancomycin was performed, and explore the appropriate methods for evaluating renal function in patients with DMD based on serum levels of creatinine and cystatin C.
Creatinine ; Cystatin C ; Drug Monitoring* ; Glomerular Filtration Rate ; Humans ; Muscular Dystrophy, Duchenne* ; Renal Elimination ; Vancomycin*

Cytochrome P450 (CYP) 3A enzymes, the most important phase 1 drug-metabolizing enzymes, are responsible for 50% of the metabolism of clinically used drugs. CYP3A activity varies widely among individuals, which can affect the probability of adverse drug reactions and drug-drug interactions mediated by the induction or inhibition of the enzyme. Hence, it is important to be able to predict CYP3A activity in individuals to reduce the incidence of unexpected drug responses. To specifically and quickly measure CYP3A activity, we developed method based on gas chromatography interfaced with triple-quadrupole mass spectrometry for the quantification of cortisol, cortisone, 6β-hydroxycortisol, and 6β-hydroxycortisone simultaneously in urine and 4β-hydroxycholesterol in plasma. The results were calculated based on charcoal-stripped steroid-free urine and plasma control samples. The accuracy and precision were 93.18% to 110.0% and 1.96% to 5.34%, respectively. This method was then applied to measure endogenous steroids from urine and plasma samples of healthy Korean males and females. The calibration curves of all analytes showed good linearity with a correlation coefficient (r2) that ranged from 0.9953 to 0.9999. Therefore, this validated method can be used to measure endogenous biomarkers to predict CYP3A activity and might be applicable in the prediction of CYP3A-mediated drug interactions of new drug candidates.

Levofloxacin is a bactericidal broad spectrum antibiotic against Gram-positive and Gram-negative pathogens. A randomized, two-treatment, two-period, two-way crossover study was conducted to evaluate the bioequivalence of Lectacin 250 mg tablet, a generic levofloxacin, to its reference drug, Cravit 250 mg tablet. Each period was separated by a 7-day washout. Serial blood samples were collected until 24 h after dosing and plasma levofloxacin concentrations were determined using a high performance liquid chromatography. Pharmacokinetic parameters were analyzed using K-BE Test 2007 and BA calc 2007 (Ministry of Food and Drug Safety, Cheongju-si, South Korea). The peak concentration (Cmax) and the area under the plasma concentration versus time curve from 0 to the last measurable concentration (AUC(0-t)) for the generic and reference levofloxacin were 4.48+/-0.89 mg/L and 4.46+/- 0.95 mg/L, and 25.33+/-4.12 mg*h/L and 25.77+/-4.01 mg*h/L, respectively, leading to a geometric mean ratio (90% confidence interval) of the generic to the reference levofloxacin of 1.0060 (0.9339-1.0842) and 0.9810 (0.9476-1.0159), respectively, for Cmax and AUC(0-t). Lectacin 250 mg tablet is bioequivalent to Cravit 250 mg tablet.
Chromatography, Liquid ; Chungcheongbuk-do ; Cross-Over Studies ; Humans ; Levofloxacin* ; Male ; Pharmacokinetics ; Plasma ; Tablets* ; Therapeutic Equivalency*

BACKGROUND: Eplerenone is a selective mineralocorticoid receptor antagonist which effectively blocks mineralocorticoid receptors in various tissues throughout the body. The addition of eplerenone to optimal medical therapy reduces morbidity and mortality among patients post acute myocardial infarction complicated by left ventricular dysfunction and heart failure. The aim of this study was to evaluate pharmacokinetic characteristics and tolerability after multiple oral administration of eplerenone 100 mg for 7 days in healthy Korean volunteers. METHODS: A double-blind, randomized, placebo-controlled, parallel study was conducted in 22 healthy Korean subjects. Healthy males and females between age of 20 and 55 years were enrolled. Each subject received 100 mg eplerenone (N=16) or placebo (N=6) for 7 days. Blood samples for pharmacokinetic parameter determination on day 7 were collected pre-dose and up to 36 hours after last drug administration. Adverse events were reported throughout the treatment period. RESULTS: The steady-state concentration of eplerenone reached after multiple administration of eplerenone 100 mg for 7 days. The mean eplerenone Cmax of 1620.1 ng/mL was obtained at 1.0 hour (range 0.5 to 2 hours). The mean AUC0-24h,ss at day 7 was 8763.6 ng/mL*h. The mean oral clearance and mean terminal half-life of eplerenone were 13.0 L/h and 3.4 hours. There were some drug-related mild adverse events after eplerenone administration, but all adverse events recovered without any treatment. CONCLUSION: In this study, the pharmacokinetic parameters after multiple oral doses of eplerenone 100 mg for 7 days were evaluated and eplerenone at these doses were well tolerated in healthy Korean subjects.
Administration, Oral ; Female ; Half-Life ; Heart Failure ; Humans ; Male ; Myocardial Infarction ; Receptors, Mineralocorticoid ; Spironolactone ; Ventricular Dysfunction, Left

The current guidelines for therapeutic drug monitoring (TDM) of vancomycin suggest a target 24-hour area under the curve (AUC 0-24 ) of 400 to 600 mg*h/L for serious methicillinresistant Staphylococcus aureus infections. In this study, the predictabilities of acute kidney injury (AKI) of various TDM target parameters, target levels, and sampling methods were evaluated in patients who underwent TDM from January 2020 to December 2020. The AUC 0-24 and trough values were calculated by both one- and two-point sampling methods, and were evaluated for the predictability of AKI. Among the AUC 0-24 cutoff comparisons, the threshold value of 500 mg*h/L in the two sampling methods was statistically significant (P = 0.042) when evaluated for the predictability of AKI. Analysis by an receiver operating characteristic curve estimated an AUC 0-24 cutoff value of 563.45 mg*h/L as a predictor of AKI, and was proposed as the upper limit of TDM target.