Development of a sensitive and quantitative UHPLC-MS/MS method to study the whole-body uptake of pharmaceuticals in zebrafish

An analytical procedure to measure the whole-body uptake of pharmaceuticals in zebrafish has been developed using state-of-the-art methodologies. A sample preparation procedure for 9 pharmaceuticals displaying a variety in physicochemical properties was developed using 10-day old zebrafish (TG898). For an efficient homogenization of the samples and subsequent recovery of the compounds of interest, different amounts of organic solvents in combination with acidic modifiers were added to zebrafish samples. Samples were subsequently processed using a powerful bath sonicator and centrifuged. Supernatant was then removed and evaporated in a vacuum oven before being reconstituted in a mobile phase-like solvent. Samples were analyzed using ultra-high performance liquid chromatography (UHPLC) on an Acquity BEH C₁₈ column (100 × 2.1mm, d_p=1.7µm) coupled to a Waters Xevo TQ-S mass spectrometer. For this purpose, a generic gradient was run, wherein the percentage of acetonitrile was varied from 3% to 82% in 10.5min at a flow rate of 0.41mL/min. Linearity of the method was demonstrated for all compounds (R² > 0.997) in a practically relevant concentration range. Matrix effects were between 81% and 106%, except for amitriptyline (51%). Using this method, it was demonstrated that a sample pretreatment using 1:2 (v/v) water:methanol in combination with 0.1% formic acid resulted in acceptable recoveries between 74% and 100% for all compounds. Together with the obtained lower limits of quantification of the analytical method (between 0.005 and 1.5ng/mL), this allowed the use of a single zebrafish to study the whole-body uptake of a particular drug, after incubating zebrafish at the maximum tolerated concentration for this drug.

Gastrointestinal behavior of itraconazole in humans - Part 2: The effect of intraluminal dilution on the performance of a cyclodextrin-based solution

Hydroxypropyl-β-cyclodextrin (HP-β-CD) is known to enable absorption of the lipophilic drug itraconazole. Since the interaction between HP-β-CD and itraconazole is characterized by a non-lineair, A_P-type phase-solubility diagram, the present study aimed to investigate the influence of intraluminal dilution (water intake) on the behavior and performance of an orally administered cyclodextrin-based solution of itraconazole. Subsequently, the in vivo behavior was simulated by combining in vitro dilution with permeation assessment. After the administration of a Sporanox^® solution to healthy volunteers with or without a glass of water, gastrointestinal and systemic concentrations of itraconazole were simultaneously monitored. Independently of the intake of water, no gastric precipitation of itraconazole was observed. After transfer to the duodenum, precipitation occurred and was more pronounced in the condition with water, resulting in a 7.6-fold reduction in duodenal AUC_0-3h compared to the condition without water. Nevertheless, plasma concentration-time profiles did not demonstrate any significant differences in AUC_0-8h, C_max and t_max. Application of freshly aspirated intestinal fluids on Caco-2 cells clearly confirmed that higher intestinal itraconazole concentrations after intake of Sporanox^® without water do not generate a substantially increased itraconazole uptake. A two-stage in vitro dilution test was combined with a permeation compartment to capture this solubility-permeability interplay. In conclusion, this work demonstrates that variations in intraluminal dilution may have a drastic impact on the gastrointestinal behavior of lipophilic drugs in the presence of cyclodextrins. In the case of an AP-type interaction with cyclodextrins, the trade-off between solubility and permeability may be affected.

Inter-Subject Variability in OCT1 Activity in 27 Batches of Cryopreserved Human Hepatocytes and Association with OCT1 mRNA Expression and Genotype

PURPOSE

OCT1/3 (Organic Cation Transporter-1 and -3; SLC22A1/3) are transmembrane proteins localized at the basolateral membrane of hepatocytes. They mediate the uptake of cationic endogenous compounds and/or xenobiotics. The present study was set up to verify whether the previously observed variability in OCT activity in hepatocytes may be explained by inter-individual differences in OCT1/3 mRNA levels or OCT1 genotype.

METHODS

Twenty-seven batches of cryopreserved human hepatocytes (male and female, age 24-88 y) were characterized for OCT activity, normalized OCT1/3 mRNA expression, and OCT1 genetic mutation. ASP⁺ (4-[4-(dimethylamino)styryl]-N-methylpyridinium iodide) was used as probe substrate.

RESULTS

ASP⁺ uptake ranged between 75 ± 61 and 2531 ± 202 pmol/(min × million cells). The relative OCT1 and OCT3 mRNA expression ranged between 0.007-0.46 and 0.0002-0.005, respectively. The presence of one or two nonfunctional SLC22A1 alleles was observed in 13 batches and these exhibited significant (p = 0.04) association with OCT1 and OCT3 mRNA expression. However, direct association between genotype and OCT activity could not be established.

CONCLUSION

mRNA levels and genotype of OCT only partially explain inter-individual variability in OCT-mediated transport. Our findings illustrate the necessity of in vitro transporter activity profiling for better understanding of inter-individual drug disposition behavior.

Atmospheric Pressure Ionization Using a High Voltage Target Compared to Electrospray Ionization

A new atmospheric pressure ionization (API) source, viz. UniSpray, was evaluated for mass spectrometry (MS) analysis of pharmaceutical compounds by head-to-head comparison with electrospray ionization (ESI) on the same high-resolution MS system. The atmospheric pressure ionization source is composed of a grounded nebulizer spraying onto a high voltage, cylindrical stainless steel target. Molecules are ionized in a similar fashion to electrospray ionization, predominantly producing protonated or deprotonated species. Adduct formation (e.g., proton and sodium adducts) and in-source fragmentation is shown to be almost identical between the two sources. The performance of the new API source was compared with electrospray by infusion of a mix of 22 pharmaceutical compounds with a wide variety of functional groups and physico-chemical properties (molecular weight, logP, and pKa) in more than 100 different conditions (mobile phase strength, solvents, pH, and flow rate). The new API source shows an intensity gain of a factor 2.2 compared with ESI considering all conditions on all compounds tested. Finally, some hypotheses on the ionization mechanism, similarities, and differences with ESI, are discussed. Graphical Abstract ᅟ.

In vitro evaluation of the impact of gastrointestinal transfer on luminal performance of commercially available products of posaconazole and itraconazole using BioGIT

Biorelevant Gastrointestinal Transfer system (BioGIT) has been shown to be useful in reproducing concentrations of drugs in the fasted upper small intestine after their administration in the stomach. In the present investigation, we evaluated the impact of gastrointestinal transfer on luminal performance of commercially available products of two highly lipophilic weak bases, posaconazole (Noxafil^® suspension) and itraconazole (Sporanox^® hard gelatin capsules and Sporanox^® oral solution) by comparing % solid fraction, concentrations and supersaturation in the duodenal compartment of BioGIT with recently reported data in the upper small intestine of healthy adults. BioGIT was useful for estimating the % solid fraction in the upper small intestine, in cases where dissolution during gastric residence was incomplete, i.e. after administration of Noxafil^® and Sporanox^® capsules, and the precipitated fraction of itraconazole in the upper small intestine after administration of Sporanox^® solution; median values in vitro were similar to the luminal values. Based on the values for the area under the concentration vs. time data estimated up to 45min post initiation of the experiment, concentrations in the duodenal compartment of BioGIT were similar to previously measured concentrations in the upper small intestine of healthy adults or they overestimated them by up to 2.5 times. In most cases, supersaturation of contents in the upper small intestine was overestimated, partly due to underestimation of luminal solubility.

Micronutrient intake, from diet and supplements, and association with status markers in pre- and post-RYGB patients

BACKGROUND & AIMS

Roux-en-Y gastric bypass (RYGB) is associated with an increased risk for micronutrient deficiencies. This study aimed to assess total (dietary and supplement) intake and association with iron (including hepcidin), vitamin B₁₂, vitamin C and zinc status markers before and after Roux-en-Y gastric bypass (RYGB).

METHODS

This prospective study included patients with a planned RYGB in University Hospitals Leuven, Belgium; who were followed until 12 months post-RYGB. Patients completed an estimated dietary record of two non-consecutive days before and 1, 3, 6 and 12 months post-RYGB and supplement/drug use was registered. Associations between total micronutrient intake and status markers were analyzed.

RESULTS

Fifty-four patients (21 males; mean age: 48.0 [95%CI 46.6; 49.3] years; mean preoperative BMI: 40.4 [95%CI 39.4; 41.4] kg/m²) were included. One month post-RYGB, usual dietary intake of the studied micronutrients was significantly decreased compared to pre-RYGB, but gradually increased until 12 months post-RYGB, remaining below baseline values. By including micronutrient supplement intake, 12 months post-RYGB values were higher than baseline, except for zinc. Hemoglobin, ferritin, vitamin B₁₂ and C-reactive protein serum concentrations were significantly decreased and transferrin saturation and mean corpuscular volume were significantly increased 12 months post-RYGB. Serum hepcidin concentration was significantly decreased 6 months post-RYGB.

CONCLUSIONS

Medical nutritional therapy is essential following RYGB as dietary intake of iron, vitamin B₁₂, vitamin C, copper and zinc was markedly decreased postoperatively and some patients still had an inadequate total intake one year post-RYGB.

Drug disposition before and after gastric bypass: fenofibrate and posaconazole

AIMS

Roux-en-Y gastric bypass (RYGB) alters the anatomical structure of the gastrointestinal tract, which can result in alterations in drug disposition. The aim of the present study was to evaluate the oral disposition of two compounds belonging to the Biopharmaceutical Classification System Class II - fenofibrate (bile salt-dependent solubility) and posaconazole (gastric pH-dependent dissolution) - before and after RYGB in the same individuals.

METHODS

A single-dose pharmacokinetic study with two model compounds - namely, 67 mg fenofibrate (Lipanthyl®) and 400 mg posaconazole (Noxafil®) - was performed in 12 volunteers pre- and post-RYGB. After oral administration, blood samples were collected at different time points up to 48 h after administration. Plasma concentrations were determined by high-performance liquid chromatography in order to calculate the area under the concentration-time curve up to 48 h (AUC_0-48 h ), the peak plasma concentration (C_max) and the time to reach peak concentration (T_max ).

RESULTS

After administration of fenofibrate, no relevant differences in AUC_0-48 h , C_max and T_max between the pre- and postoperative setting were observed. The geometric mean of the ratio of AUC_0-48 h post/pre-RYGB for fenofibrate was 1.10 [95% confidence interval (CI) 0.87, 1.40; P = 0.40]. For posaconazole, an important decrease in AUC_0-48 h and C_max following RYGB was shown; the geometric mean of the AUC_0-48 h post/pre-RYGB ratio was 0.68 (95% CI 0.48, 0.96; P = 0.03) and the geometric mean of the C_max pre/post-RYGB ratio was 0.60 (95% CI 0.39, 0.94; P = 0.03). The decreased exposure of posaconazole could be explained by the increased gastric pH and accelerated gastric emptying of fluids post-RYGB. No difference for T_max was observed.

CONCLUSIONS

The disposition of fenofibrate was not altered after RYGB, whereas the oral disposition of posaconazole was significantly decreased following RYGB.

Metabolism, Protein Binding, and Renal Clearance of Microbiota-Derived p-Cresol in Patients with CKD

BACKGROUND AND OBJECTIVES

Colonic microbial metabolism substantially contributes to uremic retention solutes in CKD. p-Cresyl sulfate is the main representative of this group of solutes, relating to adverse outcomes. Other than sulfate conjugation, p-cresol is subjected to endogenous glucuronide conjugation. Whether the balance between sulfate and glucuronide conjugation is relevant in CKD is unexplored.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We prospectively followed 488 patients with CKD stages 1-5 (enrollment between November of 2005 and September of 2006; follow-up until December of 2010). Serum and urine levels of p-cresyl sulfate and p-cresyl glucuronide were measured using liquid chromatography-mass spectrometry. Total amount of microbial p-cresol was calculated by the sum of serum p-cresyl sulfate and p-cresyl glucuronide. Outcome analysis was performed for mortality and cardiovascular disease.

RESULTS

Serum p-cresyl sulfate was a median of 193.0-fold (interquartile range, 121.1-296.6) higher than serum p-cresyl glucuronide, with a significant correlation between eGFR and proportion of serum p-cresyl sulfate to glucuronide (rho=0.23; P=0.001). There was also a significant correlation between eGFR and proportion of 24-hour urinary excretion of p-cresyl sulfate to glucuronide (rho=0.32; P<0.001). Higher serum p-cresol and lower proportion of serum p-cresyl sulfate to glucuronide were jointly and significantly associated with mortality (hazard ratio per SD higher, 1.58; 95% confidence interval, 1.10 to 2.29; P=0.01 and hazard ratio, 0.65; 95% confidence interval, 0.47 to 0.89; P<0.01, respectively) and cardiovascular disease (hazard ratio, 1.68; 95% confidence interval, 1.27 to 2.22; P<0.001 and hazard ratio, 0.55; 95% confidence interval, 0.42 to 0.72; P<0.001, respectively) after adjustment for eGFR, Framingham risk factors, mineral bone metabolism markers, C-reactive protein, and albumin.

CONCLUSIONS

p-Cresol shows a preponderance of sulfate conjugation, although a relatively diminished sulfotransferase activity can be suggested in patients with advanced CKD. Along with total p-cresol burden, a relative shift from sulfate to glucuronide conjugation is independently associated with mortality and cardiovascular disease, warranting increased focus to the dynamic interplay between microbial and endogenous metabolism.

In vitro and in vivo investigation of the gastrointestinal behavior of simvastatin

Simvastatin (SV) is marketed as a lactone ester prodrug which is hydrolyzed to the active simvastatin hydroxyacid (SVA). SV is characterized by a low solubility and undergoes extensive first-pass metabolism. In this study, the influence of the upper gastrointestinal environment on the intraluminal behavior of simvastatin was investigated by a series of in vitro experiments. Dissolution, stability and two-stage dissolution tests were performed using simulated and human gastrointestinal fluids. The dissolution studies revealed a relatively slow dissolution of SV as well as conversion of SV to SVA. The hydrolysis of SV was further examined and stability studies indicated a faster conversion in gastric fluids than in intestinal fluids. These isolated phenomena were then confirmed by the more integrative two-stage dissolution studies. To estimate the predictive value of the in vitro tests, an additional in vivo study was performed in which the gastrointestinal concentration-time profiles also revealed a slow dissolution of SV and faster degradation of SV to SVA in the stomach than in the intestinal tract. However, the plasma concentrations of SV and SVA did not directly correlate with the observed gastrointestinal concentrations, suggesting that gut wall and hepatic metabolism have a greater impact on systemic exposure of SV than the intraluminal interconversion between SV and SVA.

Investigation of Saliva as an Alternative to Plasma Monitoring of Voriconazole

BACKGROUND AND OBJECTIVES

Therapeutic drug monitoring (TDM) of voriconazole is increasingly being implemented in clinical practice. However, as blood sampling can be difficult in paediatric and ambulatory patients, a non-invasive technique for TDM is desirable. The aim of this study was to compare the pharmacokinetics of voriconazole in saliva with the pharmacokinetics of unbound and total voriconazole in plasma in order to clinically validate saliva as an alternative to plasma in voriconazole TDM.

METHODS

In this pharmacokinetic study, paired plasma and saliva samples were taken at steady state in adult haematology and pneumology patients treated with voriconazole. Unbound and bound plasma voriconazole concentrations were separated using high-throughput equilibrium dialysis. Voriconazole concentrations were determined with liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were calculated using log-linear regression.

RESULTS

Sixty-three paired samples were obtained from ten patients (seven haematology and three pneumology patients). Pearson's correlation coefficients (R values) for saliva versus unbound and total plasma voriconazole concentrations showed a very strong correlation, with values of 0.970 (p < 0.001) and 0.891 (p < 0.001), respectively. Linear mixed modelling revealed strong agreement between voriconazole concentrations in saliva and unbound plasma voriconazole concentrations, with a mean bias of -0.03 (95 % confidence interval -0.14 to 0.09; p = 0.60). For total concentrations below 10 mg/L, the mean ratio of saliva to total plasma voriconazole concentrations was 0.51 ± 0.08 (n = 63), which did not differ significantly (p = 0.76) from the unbound fraction of voriconazole in plasma of 0.49 ± 0.03 (n = 36).

CONCLUSIONS

Saliva can serve as a reliable alternative to plasma in voriconazole TDM, and it can easily be implemented in clinical practice.