Validation of an Isavuconazole High-Performance Liquid Chromatography Assay in Plasma for Routine Therapeutic Drug Monitoring Applications.

BACKGROUND: Isavuconazole is a triazole antifungal agent for treatment of invasive aspergillosis and mucormycosis. At present, it is unclear whether a therapeutic drug monitoring (TDM) of isavuconazole would be necessary. The aim of the investigation was to validate a high-performance liquid chromatography (HPLC) assay for routine applications. METHODS: An HPLC assay for routine determination of isavuconazole in plasma has been adapted and validated. The assay used the reagents and HPLC column provided by the ChromSystems HPLC Kit for TDM of itraconazole, posaconazole, and voriconazole. Isocratic flow rate was set at 1.0 mL/min. Detection was performed using a fluorescence detector with excitation wavelength set at 261 nm and emission wavelength set at 366 nm. RESULTS: The assay was linear between 0.15 and 10 mg/L with intraday and interday imprecision and accuracy <10% (<20% at lower limit of quantification). The method was applied to routine TDM of 7 patients after hematopoietic stem cell transplantation (n = 31 samples). In these patients, trough levels ranged from 0.45 to 3.06 mg/L (median 1.44 mg/L). CONCLUSIONS: A robust and simple HPLC assay of isavuconazole in plasma for routine TDM applications is presented.

Evaluation of limited sampling models for prediction of oral midazolam AUC for CYP3A phenotyping and drug interaction studies.

BACKGROUND: The area under the concentration-time curve (AUC) after oral midazolam administration is commonly used for cytochrome P450 (CYP) 3A phenotyping studies. The aim of this investigation was to evaluate a limited sampling strategy for the prediction of AUC with oral midazolam. METHODS: A total of 288 concentration-time profiles from 123 healthy volunteers who participated in four previously performed drug interaction studies with intense sampling after a single oral dose of 7.5 mg midazolam were available for evaluation. Of these, 45 profiles served for model building, which was performed by stepwise multiple linear regression, and the remaining 243 datasets served for validation. Mean prediction error (MPE), mean absolute error (MAE) and root mean squared error (RMSE) were calculated to determine bias and precision RESULTS: The one- to four-sampling point models with the best coefficient of correlation were the one-sampling point model (8 h; r (2) = 0.84), the two-sampling point model (0.5 and 8 h; r (2) = 0.93), the three-sampling point model (0.5, 2, and 8 h; r (2) = 0.96), and the four-sampling point model (0.5,1, 2, and 8 h; r (2) = 0.97). However, the one- and two-sampling point models were unable to predict the midazolam AUC due to unacceptable bias and precision. Only the four-sampling point model predicted the very low and very high midazolam AUC of the validation dataset with acceptable precision and bias. The four-sampling point model was also able to predict the geometric mean ratio of the treatment phase over the baseline (with 90 % confidence interval) results of three drug interaction studies in the categories of strong, moderate, and mild induction, as well as no interaction. CONCLUSION: A four-sampling point limited sampling strategy to predict the oral midazolam AUC for CYP3A phenotyping is proposed. The one-, two- and three-sampling point models were not able to predict midazolam AUC accurately.

Intraindividual long term stability and response corridors of cytokines in healthy volunteers detected by a standardized whole-blood culture system for bed-side application.

BACKGROUND: The variation of immune cell activities over time is an immanent property of the human immune system, as can be measured by the stimulated secretion of cytokines in cell cultures. However, inter-individual variability is considerably higher. Especially the latter is the major reason why it has not been possible to establish international standard values for cytokines as was possible for other parameters, such as leukocyte sub-population numbers. In this trial, a highly standardized whole-blood culture model (TrueCulture®), developed to characterise drug effects on cells of the human immune system in clinical trials, was used to analyse cytokine patterns in the blood samples of 12 healthy subjects over a period of one month. METHODS: After an overnight fast, 12 healthy subjects donated blood three times a week on three consecutive days over a period of 4 weeks. TruCulture® blood collection and whole-blood culture systems were used to measure whole-blood leukocyte stimulation. The levels of IL-2, IL-5, IL-13, IL-6, IL-8, IL-10, IFNγ, and MCP-1 in the culture supernatants were quantified by sandwich ELISA. RESULTS: The pattern of cytokine concentrations in the supernatants of the stimulated whole-blood cultures was highly individual, but considerably stable over the whole observation period of 4 weeks. CONCLUSIONS: By using TruCulture® it seems feasible to determine subject-specific cytokine reference patterns, for example under healthy conditions, or before starting an experimental treatment, e.g. during a clinical trial, against which changes in the behaviour of the immune system can be detected more accurately in future.

Periprosthetic Fungal Infections in Severe Endoprosthetic Infections of the Hip and Knee Joint-A Retrospective Analysis of a Certified Arthroplasty Centre of Excellence.

The treatment of periprosthetic joint infections (PJI), and especially of re-infections, poses a highly complex problem in orthopaedic surgery. While fungal infections are rare, they present a special challenge. The therapy is often protracted and based on limited evidence. A total of 510 hip and knee revision surgeries were analysed for the occurrence of bacterial and fungal PJI. In patients with PJI, the duration of the hospital stay and the incidence of disarticulation of the infected joint were recorded. Out of the analysed revision arthroplasties, 43.5% were due to PJI. Monomicrobial infection occurred in 55.2%, dual microbial infection in 21.4%, and polymicrobial (≥3 different bacterial or fungal species) infection in 17.2% of the cases. Overall, Candida species were detected in 12.4% cases. Candida albicans was the main fungal pathogen. In 6.9% of cases, disarticulation of the joint was the only option to control PJI. The detection of polymicrobial infection more than doubled in follow-up revisions and there was a strong association between detection of Candida infection and disarticulation (OR 9.39). The majority of fungal infections were mixed infections of bacteria and Candida albicans. The choice of a biofilm penetrating antimycotic, e.g., caspofungin, together with a sufficient standard procedure for detection and surgical treatment can help to control the infection situation. Fungal infection often proves to be more difficult to treat than anticipated and is more frequent than expected.

No clinically relevant CYP3A induction after St. John's wort with low hyperforin content in healthy volunteers.

OBJECTIVE: Induction of CYP3A by St. John's wort (SJW) products with high hyperforin content is well described. Since CYP3A induction is mediated by hyperforin in a concentration-dependent manner, and SJW preparations differ significantly in hyperforin content, the aim of the study was to evaluate the effect of an SJW powder with low hyperforin content on CYP3A function. METHODS: Twenty healthy male volunteers received an SJW powder with low hyperforin content for 2 weeks. Midazolam plasma concentration time profiles were characterized after a single oral dose of 7.5 mg midazolam on the day before and on the 14th day of SJW medication. RESULTS: Midazolam AUC(0-infinity) slightly decreased from 124.0 +/- 62.5 ng/ml.h at baseline to 105.6 +/- 53.2 ng/ml.h after SJW (P < 0.05), representing a mean 11.3% decrease (95% CI: -22.8 to 0.21). No significant change in midazolam C(max), t(1/2) and t(max) was observed. For all pharmacokinetic parameters, the 90% CI for the geometric mean ratio of treatment over baseline were within the no-effect boundaries of 0.70-1.43. CONCLUSION: Administration of an SJW product with low hyperforin content resulted in a mild induction of CYP3A not considered clinically relevant.

Effect of St John's wort dose and preparations on the pharmacokinetics of digoxin.

BACKGROUND AND OBJECTIVE: St John's wort preparations vary in composition, main constituents, formulation, and daily dose administered. The aim of the study was to evaluate the possible pharmacokinetic interaction of marketed St John's wort formulations and doses with digoxin. METHODS: A randomized, placebo-controlled, parallel-group study was performed in 96 healthy volunteers in 3 study parts. A 7-day loading phase with digoxin was followed by 14 days of comedication with placebo or one of 10 St John's wort products varying in dose and formulation. The pharmacokinetics of digoxin was determined before comedication and on day 14 of comedication. RESULTS: Comedication comprised traditionally used Hypericum products; 2 g powder without hyperforin, tea, juice, oil extract, and placebo had no significant interaction with digoxin nor did hyperforin-free extract (Ze 117) or low daily doses of hyperforin-containing Hypericum powder (1 g, 0.5 g). However, comedication with the high-dose hyperforin-rich extract LI 160 resulted in a reduction of digoxin area under the curve from time 0 to 24 hours (AUC(0-24)) of -24.8% (95% confidence interval [CI], -28.3 to -21.3), a reduction in digoxin maximal plasma concentration (C(max)) of -37% (95% CI, -42 to -32), and a reduction in digoxin plasma concentration at 24 hours after previous dosing (C(trough)) of -19% (95% CI, -27 to -11). Comedication with 4 g Hypericum powder with comparable hyperforin content resulted in a reduction in digoxin AUC(0-24) of -26.6% (95% CI, -37.3 to -15.9), a reduction in digoxin C(max) of -38% (95% CI, -48 to -18), and a reduction in digoxin C(trough) of -19% (95% CI, -27 to -10). Two grams of Hypericum powder with half the hyperforin content resulted in a less prominent reduction in AUC(0-24) of -17.7% (95% CI, -21.6 to -13.7), C(max) (-21%; 95% CI, -40 to -2), and C(trough) (-13%; 95% CI, -21 to -5). CONCLUSIONS: The interaction of St John's wort and digoxin varies within St John's wort preparations and doses and seems to be correlated with the dose, particularly of hyperforin.

The extent of induction of CYP3A by St. John's wort varies among products and is linked to hyperforin dose.

OBJECTIVE: Induction of CYP3A by St. John's wort (SJW) extracts with high hyperforin (HYF) content is well described. Since SJW products vary in the amount of HYF and other main constituents, the aim of the study was to evaluate the effect on CYP3A function of SJW preparations with a range from very low to high HYF content. METHODS: Forty-two male, healthy volunteers were randomized into six parallel SJW medication groups with varying composition especially with regard to HYF content. Midazolam plasma concentration profiles were characterized after a single oral dose of 7.5 mg midazolam on the day before and on the 14th day of SJW medication. RESULTS: All SJW preparations tested resulted in a decrease in midazolam AUC, although the extent of the effect differed. The extract LI 160 (HYF 41 mg/day) decreased midazolam AUC0-12h by 79.4% (95% CI -88.6; -70.1), which was significantly greater than the effect by any other medication (p<0.05). SJW powder tablets 2.7 g/day (HYF 12 mg/day) resulted in a midazolam AUC0-12h decrease of 47.9% (95% CI -59.7;-36.2), while 2.7 g/day SJW powder tablets that were almost devoid of HYF (0.13 mg/day) reduced midazolam AUC0-12h by only 21.1% (95% CI -33.9; -8.3). Considering all six SJW medications tested, the extent of midazolam AUC decrease correlated significantly with increasing HYF dose (r=-0.765, p<0.001), but not with hypericin dose (r=-0.067; p=0.673). CONCLUSION: The extent of induction of CYP3A varies among St. John's wort products and depends on hyperforin dose.

Pharmacokinetics of piperacillin-tazobactam in anuric intensive care patients during continuous venovenous hemodialysis.

The pharmacokinetics of piperacillin-tazobactam were investigated in eight anuric intensive care patients treated by continuous venovenous hemodialysis (CVVHD). The elimination half-life of piperacillin was 4.3 +/- 1.2 h, and that of tazobactam was 5.6 +/- 1.3 h. The contribution of CVVHD to the overall elimination was relevant (>25%) for both drugs.