Propranolol and metoprolol: Two comparable drugs with very different post-mortem toxicological profiles.

Propranolol is a widely used beta-blocker mainly prescribed for the treatment of hypertension and other cardiac conditions. This medicine is also a frequent finding in drug screens, but little is known about its post-mortem toxicological profile. Our aim was to examine all post-mortem toxicology cases positive for propranolol in a three-year period, between 2016 and 2018 in Finland, and to compare these cases to those positive for metoprolol, another beta-blocker commonly used to treat cardiac diseases. There were 179 cases positive for propranolol and 416 for metoprolol in the study period. In the majority of propranolol cases (53%), the drug concentration in the blood was above the typical therapeutic range, but among the metoprolol cases this proportion was 18%. Propranolol was significantly more common than metoprolol in fatal poisonings, suicides and in cases with a history of drug abuse. Alcohol, benzodiazepines, antipsychotics and antidepressants were significantly more often detected in propranolol cases than in metoprolol cases. The deceased positive for propranolol were significantly younger than those positive for metoprolol. Cardiovascular diseases as the underlying cause of death were significantly more common among the metoprolol cases than among the propranolol cases. Our results showed significant differences between the propranolol group and the metoprolol group in post-mortem toxicology cases. The two drugs were used by two very different groups of people, with propranolol use being associated with psychiatric conditions.

Sensitive Analysis of Metoprolol Tartrate and Diltiazem Hydrochloride in Human Serum by Capillary Zone Electrophoresis Combining on Column Field-Amplified Sample Injection.

A sensitive capillary zone electrophoresis (CZE) combined with field-amplified sample injection (FASI) method was investigated to simultaneously determine diltiazem (DI) hydrochloride and metoprolol (ME) tartrate in human serum. This method was validated by linearity, limits of detection (LOD), stability, precision and accuracy, and the related parameters are linearity (r2 > 0.9980), intra- and inter-day precisions (intra-day relative standard deviation (RSD) is 2.3-3.4%, and inter-day RSD is 3.8-7.5%) and the LOD (0.02 ng/mL for ME tartrate and 0.01 ng/mL for DI hydrochloride). So the proposed method is rapid, sensitive and accurate for determination of these two anti-anginal drugs in human serum. As for enrichment conditions, it was helpful to add phosphoric acid and isopropanol into samples for enrichment efficiency. A model was established to illustrate the possible enrichment mechanism of analytes, and a theory of half-width was also applied in CZE combined with FASI method to evaluate the peak performance.

Quantification of serum levels in mice of seven drugs (and six metabolites) commonly taken by older people with polypharmacy.

Polypharmacy (use of ≥ 5 drugs) is common in older people but has minimal preclinical or clinical evidence of safety or efficacy and is associated with adverse outcomes in older people. Drug-drug interactions are poorly understood beyond drug pairs. An efficient and sensitive method to measure multiple serum drugs and metabolites could inform drug dosing in polypharmacy. Development of a sensitive liquid chromatography - tandem mass spectrometry method to simultaneously measure seven drugs and their respective metabolites in serum in a preclinical model of polypharmacy. This method was validated for optimal recovery, matrix effect, limit of quantification (LOQ), inter- and intra-day variability, and carry over. Serum samples from mice (n = 5-6/group) treated with chronic oral doses of three polypharmacy regimens and five monotherapies were screened for drug and metabolite levels (metoprolol, α-hydroxymetoprolol, O-desmethylmetoprolol, omeprazole, 5-hydroxyomeprazole, omeprazole sulphone, acetaminophen, irbesartan, citalopram, oxybutynin, oxycodone, noroxycodone, oxymorphone and tenivastatin). The LOQ for the compounds ranged from 0.05 to 0.1 ng/mL in serum. Recovery, matrix effect, and inter- and intra-day variability peak response were acceptable. No carry over was observed at the concentrations tested. Analytes were detectable in mice treated with these drugs, and differences in drug levels were observed with different polypharmacy and monotherapy regimens. The method is sensitive and robust to measure parent drugs and metabolites simultaneously in the context of polypharmacy. Polypharmacy appeared to affect drug levels in a preclinical model. This model can be used to understand pharmacokinetics of chronic polypharmacy, which could inform prescribing and improve outcomes for older people.

Direct analysis in real time-mass spectrometry for rapid quantification of five anti-arrhythmic drugs in human serum: application to therapeutic drug monitoring.

Therapeutic drug monitoring (TDM) is necessary for the optimal administration of anti-arrhythmic drugs in the treatment of heart arrhythmia. The present study aimed to develop and validate a direct analysis in real time tandem mass spectrometry (DART-MS/MS) method for the rapid and simultaneous determination of five anti-arrhythmic drugs (metoprolol, diltiazem, amiodarone, propafenone, and verapamil) and one metabolite (5-hydroxy(OH)-propafenone) in human serum. After the addition of isotope-labeled internal standards and protein precipitation with acetonitrile, anti-arrhythmic drugs were ionized by DART in positive mode followed by multiple reaction monitoring (MRM) detection. The use of DART-MS/MS avoided the need for chromatographic separation and allowed rapid and ultrahigh throughput analysis of anti-arrhythmic drugs in a total run time of 30 s per sample. The DART-MS/MS method yielded satisfactory linearity (R2 ≥ 0.9906), accuracy (86.1-109.9%), and precision (≤ 14.3%) with minimal effect of biological matrixes. The method was successfully applied to analyzing 30 clinical TDM samples. The relative error (RE) of the concentrations obtained by DART-MS/MS and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was within ± 13%. This work highlights the potential usefulness of DART for the rapid quantitative analysis of anti-arrhythmic drugs in human serum and gives rapid feedback in the clinical TDM practices.

Assessment of effects of repeated oral doses of fedratinib on inhibition of cytochrome P450 activities in patients with solid tumors using a cocktail approach.

PURPOSE: Fedratinib, an oral selective kinase inhibitor with activity against both wild type and mutationally activated Janus kinase 2, has been approved for the treatment of adult patients with intermediate-2 or high-risk myelofibrosis by the US Food and Drug Administration. In vitro studies indicated that fedratinib was an inhibitor of several cytochrome P450 (CYP) enzymes. The primary objective of this study was to evaluate the effects of repeated doses of fedratinib on the activity of CYP2D6, CYP2C19, and CYP3A4 in patients with solid tumors using a CYP probe cocktail. METHODS: An open-label, one-sequence, two-period, two-treatment crossover study was conducted. Patients were administered a single oral dose cocktail of metoprolol (100 mg), omeprazole (20 mg), and midazolam (2 mg) used as probe substrates for CYP2D6, CYP2C19, and CYP3A4 enzyme activities, respectively, without fedratinib on Day -1 or with fedratinib on Day 15. RESULTS: Coadministration of 500 mg once-daily doses of fedratinib for 15 days increased the mean area under the plasma concentration-time curve from time zero to infinity following a single-dose cocktail containing metoprolol (CYP2D6 substrate), omeprazole (CYP2C19 substrate), and midazolam (CYP3A4 substrate) by 1.77-fold (90% confidence interval [CI] 1.27-2.47) for metoprolol, 2.82-fold (90% CI 2.26-3.53) for omeprazole, and 3.84-fold (90% CI 2.62-5.63) for midazolam, respectively. The mean plasma Day 14/Day 1 ratio of 4ß-hydroxycholesterol, an endogenous biomarker of CYP3A4 activity, was 0.59 (90% CI 0.54-0.66), suggesting a net inhibition of CYP3A4 by fedratinib. CONCLUSION: Fedratinib is a weak inhibitor of CYP2D6, and a moderate inhibitor of CYP2C19 and CYP3A4. These results serve as the basis for dose modifications of these CYP substrate drugs when co-administered with fedratinib.

Effect of Roux-en-Y gastric bypass on the bioavailability of metoprolol from immediate and controlled release tablets: a single oral dose study before and after surgery.

Objective: Roux-en-Y gastric bypass (RYGB) surgery induces major changes in the gastrointestinal tract that may alter the pharmacokinetics of orally administered drugs. Results from pharmacokinetic studies are sparse. This study aimed to investigate the effect of RYGB on the bioavailability of metoprolol from immediate release (IR) and controlled release (CR) tablets in female patient volunteers before and after surgery. Methods: An explorative, two-phase, single oral dose pharmacokinetic study of metoprolol in female patients undergoing RYGB was carried out. The dose was administered twice in each patient, 1 month before and 6 months after surgery. After intake of either 100 mg of metoprolol IR or CR tablet serum concentration-time profiles of metoprolol were determined. The endpoint was the ratio of AUCafter/AUCbefore of metoprolol. Results: Twelve patients were included in the study (metoprolol IR: 7; metoprolol CR: 5). After intake of a metoprolol IR tablet major intraindividual and interindividual differences for area under the serum concentration versus time curve (AUC) of metoprolol before and after surgery were observed (range ratio AUC0-10 hours after/AUC0-10 hours before: 0.74-1.98). For metoprolol CR tablets a significant reduction in bioavailability of metoprolol was observed after surgery (range ratio AUC0-24 hours after/AUC0-24 hours before: 0.43-0.77). Conclusion: RYGB may influence the bioavailability of metoprolol from an IR tablet. The magnitude of changes in bioavailability after RYGB requires close monitoring of patients using metoprolol IR tablets and dose adjustment if deemed necessary. RYGB clearly reduces the bioavailability of metoprolol from a CR tablet. After RYGB clinicians may consider to increase the dose according to clinical response.

Impact of genotype-predicted CYP2D6 metabolism on clinical effects and tolerability of metoprolol in patients after myocardial infarction - a prospective observational study.

PURPOSE: The ß-1 adrenergic receptor blocker metoprolol is primarily metabolized by the polymorphic enzyme cytochrome P 450 2D6 (CYP2D6), an enzyme with substantial genetic heterogeneity. Our purpose was to investigate the impact of CYP2D6 metabolism on clinical effects and tolerability of metoprolol in patients after myocardial infarction (MI). METHODS: We included 136 patients with MI discharged on treatment with metoprolol with a recommendation to the general practitioner (GP) to increase the metoprolol dose up to 200 mg/day within 2 months if possible. At follow-up, metoprolol dosage after up-titration, metoprolol steady-state trough plasma concentrations, hemodynamic parameters, potential metoprolol-induced adverse drug reactions and number of visits to the GP were measured. CYP2D6 genotyping including the reduced-function variant alleles CYP2D6*9, CYP2D6*10 and CYP2D6*41 was performed after end of follow-up. RESULTS: According to the genotype-defined CYP2D6 phenotypes, 30% of the patients were metoprolol extensive metabolizers (EMs), 55% intermediate metabolizers (IMs) and 13% poor metabolizers (PMs; carriers of non-coding and reduced-function variant included). Dose-adjusted metoprolol trough concentrations were significantly higher in IM (2-fold) and PM (6.2-fold) groups vs. the EM group (p < 0.001). Only 35% of patients in the PM group achieved the primary end point, i.e. reaching at least 85% of the expected maximum heart rate (HR) during exercise, compared with 78% in the EM group (p < 0.01), and maximum observed HR at exercise was significantly lower in the PM group vs. the EM group (129 ± 5 vs. 142 ± 2 bpm, p < 0.007). In contrast, metoprolol maintenance dose, blood pressure, exercise capacity, number of visits at the GP and frequency and severity of self-reported potential metoprolol-related adverse drug reactions were not significantly different between the groups. CONCLUSION: Using a comprehensive CYP2D6 genotyping panel, the present study demonstrates a > 6-fold increase of dose-adjusted plasma metoprolol trough concentration in CYP2D6 PMs vs. EMs with a parallel lower increase in achieved maximum HR during exercise but without association between genotype and frequency or severity of self-reported adverse drug effects. This may indicate that CYP2D6 PMs potentially could benefit of the increased plasma concentration per dose in a naturalistic setting.

Evaluation of OptiFlow™-MS/MS for bioanalysis of pharmaceutical drugs and metabolites.

Aim: Microflow tandem mass spectrometry-based methods have been proposed as options to improve sensitivity and selectivity while improving sample utility and solvent consumption. Here, we evaluate a newly introduced microflow source, OptiFlow™, for quantitative performance. Results/methodology: We performed a comparison of the OptiFlow and IonDrive™ sources, respectively, on the same triple quadrupole mass spectrometer. The comparison used a neat cocktail of commercially available drugs and extracted plasma samples monitoring midazolam and alprazolam metabolites. Microflow produced a 2-4× signal increase for the neat drug cocktail and a 5-10× increase for extracted plasma samples. Conclusion: The OptiFlow method consistently gave increased signal response relative to the IonDrive method and enabled a better lower limit of quantitation for defining phamacokinetics.

High-throughput quantification of ten antiarrhythmic drugs in human plasma using UPLC-MS/MS.

In this paper we present an FDA validated method to analyze ten antiarrhythmic drugs (atenolol, bisoprolol, carvedilol, diltiazem, flecainide, lidocaine, metoprolol, propranolol, sotalol and verapamil). A simple and fast sample preparation protocol with protein precipitation followed by ultra performance liquid chromatography (UPLC) for chromatographic separation and mass spectrometric detection applying electrospray ionization (ESI+) and selected reaction monitoring mode (MS/MS) was used. Only 50 µl plasma sample is needed for the simultaneous quantification of all compounds within a 5 min run-to-run analysis time. Sotalol-D6, carvedilol-D5 and verapamil-D6 were used as internal standards. The method was validated according to the FDA guidelines. Correlation coefficients were higher than 0.998 for all compounds. Intra- and interday accuracies were within 15 CV(%) for all analytes. The method is currently successfully applied for routine analysis in our hospital.

A High Throughput HPLC-MS/MS Method for Antihypertensive Drugs Determination in Plasma and Its Application on Pharmacokinetic Interaction Study with Shuxuetong Injection in Rats.

A high-throughput HPLC-MS/MS method was developed and validated for the determination of four antihypertensive drugs including metoprolol tartrate, hydrochlorothiazide, nifedipine, and valsartan in rat plasma. The Sprague-Dawley rats were randomly divided into three groups: A Group: gastric-administration of metoprolol tartrate, hydrochlorothiazide, nifedipine, or valsartan; B Group: a single intravenous injection of SXT, then dosing as the A group; C Group: daily injection of SXT through the tail vein for 8 consecutive days and dosing as the A group on the eighth day. For metoprolol tartrate and valsartan, blood samples were collected before administration and at time points 0.03, 0.08, 0.17, 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, and 24 h from the fossa orbitalis vein. For hydrochlorothiazide and nifedipine, the time points were 0, 0.08, 0.17, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 10, 12, and 24 h. The plasma samples containing different individual antihypertensive drug were mixed and prepared by protein precipitation with methanol. The chromatographic separation was performed on an Agilent Eclipse Plus C18 column (2.1 mm×100 mm, 3.5 µm) using gradient elution with mobile phase consisting of acetonitrile and water (containing 0.1% formic acid). The flow rate was 0.3 mL/min. The detection was accomplished on a tandem mass spectrometer with an electrospray ionization (ESI) source by multiple reaction monitoring (MRM) in both positive and negative modes. The method was successfully applied to a pharmacokinetic interaction study of Shuxuetong injection on the antihypertensive drugs. The results suggested that SXT could increase the total amount of metoprolol tartrate and nifedipine in plasma and showed little influence on the pharmacokinetic behaviors of hydrochlorothiazide and valsartan.

UHPLC-MS/MS assay for simultaneous determination of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin with its active metabolites in human plasma, for population-scale drug-drug interactions studies in people living with HIV.

Thanks to highly active antiretroviral treatments, HIV infection is now considered as a chronic condition. Consequently, people living with HIV (PLWH) live longer and encounter more age-related chronic co-morbidities, notably cardiovascular diseases, leading to polypharmacy. As the management of drug-drug interactions (DDIs) constitutes a key aspect of the care of PLWH, the magnitude of pharmacokinetic DDIs between cardiovascular and anti-HIV drugs needs to be more thoroughly characterized. To that endeavour, an UHPLC-MS/MS bioanalytical method has been developed for the simultaneous determination in human plasma of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin and its active metabolites. Plasma samples were subjected to protein precipitation with methanol, followed by evaporation at room temperature under nitrogen of the supernatant, allowing to attain measurable plasma concentrations down to sub-nanogram per milliliter levels. Stable isotope-labelled analytes were used as internal standards. The five drugs and two metabolites were analyzed using a 6-min liquid chromatographic run coupled to electrospray triple quadrupole mass spectrometry detection. The method was validated over the clinically relevant concentrations ranging from 0.3 to 480 ng/mL for amlodipine, atorvastatin and p-OH-atorvastatin, and 0.4 to 480 ng/mL for pravastatin, 0.5 to 480 ng/mL for rosuvastatin and o-OH-atorvastatin, and 3 to 4800 ng/mL for metoprolol. Validation performances such as trueness (95.4-110.8%), repeatability (1.5-13.4%) and intermediate precision (3.6-14.5%) were in agreement with current international recommendations. Accuracy profiles (total error approach) were lying within the limits of ±30% accepted in bioanalysis. This rapid and robust UHPLC-MS/MS assay allows the simultaneous quantification in plasma of the major currently used cardiovascular drugs and offers an efficient analytical tool for clinical pharmacokinetics as well as DDIs studies.

Evaluation of potential herbal-drug interactions of a standardized propolis extract (EPP-AF®) using an in vivo cocktail approach.

ETHNOPHARMACOLOGICAL RELEVANCE: Propolis has been employed extensively in many cultures since ancient times as antiseptic, wound healing, anti-pyretic and others due to its biological and pharmacological properties, such as immunomodulatory, antitumor, anti-inflammatory, antioxidant, antibacterial, antiviral, antifungal, antiparasite activities. But despite its broad and traditional use, there is little knowledge about its potential interaction with prescription drugs. AIM OF THE STUDY: The main objective of this work was to study the potential herbal-drug interactions (HDIs) of EPP-AF® using an in vivo assay with a cocktail approach. MATERIALS AND METHODS: Subtherapeutic doses of caffeine, losartan, omeprazole, metoprolol, midazolam and fexofenadine were used. Sixteen healthy adult volunteers were investigated before and after exposure to orally administered 125 mg/8 h (375 mg/day) EPP-AF® for 15 days. Pharmacokinetic parameters were calculated based on plasma concentration versus time (AUC) curves. RESULTS: After exposure to EPP-AF®, it was observed decrease in the AUC0-∞ of fexofenadine, caffeine and losartan of approximately 18% (62.20 × 51.00 h.ng/mL), 8% (1085 × 999 h.ng/mL) and 13% (9.01 × 7.86 h.ng/mL), respectively, with all 90% CIs within the equivalence range of 0.80-1.25. On the other hand, omeprazole and midazolam exhibited an increase in AUC0-∞ of, respectively, approximately 18% (18.90 × 22.30 h.ng/mL) and 14% (1.25 × 1.43 h.ng/mL), with the upper bounds of 90% CIs slightly above 1.25. Changes in pharmacokinetics of metoprolol or its metabolite α-hydroxymetoprolol were not statistically significant and their 90% CIs were within the equivalence range of 0.80-1.25. CONCLUSIONS: In conclusion, our study shows that EPP-AF® does not clinically change CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A activities, once, despite statistical significant, the magnitude of the changes in AUC values after EPP-AF® were all below 20% and therefore may be considered safe regarding potential interactions involving these enzymes. Besides, to the best of our knowledge this is the first study to assess potential HDIs with propolis.

Comparing PyroMark Q24 Pyrosequencing and MALDI-TOF MS for Identification of CYP2D6*10.

BACKGROUND: CYP2D6*10 is mainly responsible for the large pharmacokinetic variability of routinely administered metoprolol in middle-aged and elderly Asian patients. Utilizing an efficient method for identifying the CYP2D6*10 genotypes is clinically important for evaluating the pharmacokinetic effect of administration of metoprolol. This study attempted to evaluate the effectiveness of the two methods used to detect the rs1065852 and rs1135840 SNPs of the CYP2D6*10 gene. METHODS: Blood samples were processed for the collection of genomic DNA from 198 subjects across Chinese population, and detection of CYP2D6*10 (rs1065852 and rs1135840) was performed using the PyroMark Q24 pyrose-quencing and matrix-assisted laser desorption/ionization time-of-flight mass-spectrometry (MALDI-TOF MS). The discordant results were further validated with Sanger sequencing. We eventually attempted to assess some features of these two methods including reliability, rapidness, being appropriate, and cost-effectiveness. RESULTS: Genotyping of rs1065852 and rs1135840 detected by MALDI-TOF MS were concordant with those identified by PyroMark Q24 pyrosequencing in all 198 (100%) individuals. The hands-on-time and the turnaround time were shorter in the PyroMark Q24 pyrosequencing method than in the MALDI-TOF MS method for SNP of CYP2D6*10. In terms of being cost-effective and high-throughput, the MALDI-TOF MS method outperformed the PyroMark Q24 pyrosequencing method. CONCLUSIONS: CYP2D6*10 genotypes detected by PyroMark Q24 pyrosequencing and MALDI-TOF-MS showed that both methods were reliable, rapid, appropriate, and cost-effective methods. These methods are valuable for clinical applications.

Effects of shuanghuanglian injection on the activities of CYP1A2, 2C11, 2D1 and 3A1/2 in rats in vivo and in vitro.

Shuanghuanglian Injection (SHLI), one of the most popular herbal prescription in China, has been commonly used to treat pneumonia, tonsillitis, and other respiratory diseases caused by bacterium and virus. This study is to investigate the effects of SHLI on the activities of Cytochrome P450 (CYP) 1A2, 2C11, 2D1 and 3A1/2 in rats. Sixteen rats were randomly divided into two groups (SHLI-treated and blank control). They were administered SHLI or physiological saline for consecutive seven days. On day eight, 16 animals were administrated cocktail drugs as probe substrates of the four CYP in vivo. In addition, other four probe drugs were added, respectively, into incubation systems of rat liver microsomes (RLM) to assess the effects of SHLI on the four CYP isoforms in vitro. SHLI exhibited an inductive effect on CYP2C11 in vivo by decreasing Cmax, t1/2 and AUC0-∞ of tolbutamide, while the main pharmacokinetic parameters of caffeine, metoprolol and dapsone have no significant changes. In vitro study, SHLI showed no significant effects on the activities of CYP1A2, 2D1 and 3A1/2, but increasing the metabolism of tolbutamide in RLM. SHLI induced the activities of CYP2C11, but had no significant effects on the activities of CYP1A2, CYP2D1 and CYP3A1/2 in rats.

A UHPLC-MS/MS method coupled with liquid-liquid extraction for the quantitation of phenacetin, omeprazole, metoprolol, midazolam and their metabolites in rat plasma and its application to the study of four CYP450 activities.

Drug-drug interactions (DDIs) are thought to be associated with the inhibition of cytochrome P450 activities. The cocktail method with analysis of the metabolism of two or more probe drugs is used to determine CYP450 activities. In this study, we established a UHPLC-MS/MS method for simultaneous quantitation of four CYP450 probe drugs (phenacetin, omeprazole, metoprolol and midazolam) and their metabolites (acetaminophen, 5'-hydroxy omeprazole, α-hydroxy metoprolol and 1'-hydroxy midazolam) in rat plasma. Sample preparation by plasma protein precipitation was combined with a liquid-liquid extraction method. The separation was carried out on a ZORBAX Eclipse Plus C18 Rapid Resolution High Definition column with a gradient elution, using water containing 0.1% formic acid (A) and acetonitrile (B) in a run time of only 3.0 min. Detection was conducted with a 6420 series triple-quadrupole tandem mass spectrometer, using ESI in positive ion mode with multiple reaction monitoring (MRM). The calibration curves were linear over the concentration range 10-5000 ng/mL for phenacetin, omeprazole, metoprolol and midazolam, and 1-500 ng/mL for their metabolites. Intra- and inter-day precisions were within 15%, and the accuracies were in the range of 87-112%. The method was successfully applied to the pharmacokinetic study of probe drugs/metabolites and DDIs with 3-n-butylphthalide (NBP) after administration of a single oral dose of phenacetin, omeprazole, metoprolol and midazolam in rats.

Reliable and easy-to-use LC-MS/MS-method for simultaneous determination of the antihypertensives metoprolol, amlodipine, canrenone and hydrochlorothiazide in patients with therapy-refractory arterial hypertension.

BACKGROUND: Therapy-refractory arterial hypertension is defined as a blood pressure (BP) in a subset of patients who fail to achieve BP control despite a three-drug regimen (including a diuretic). Various factors have impact on loss of therapy response. Drug-drug-interactions (DDIs) may cause altered pharmacokinetics (PK) of antihypertensive drugs. Upregulation of activity and expression of cytochrome P450 (CYP) enzymes can result in decreased plasma drug levels. Besides these PK considerations a significant problem could be nonadherence to drug therapy. In this regard Therapeutic Drug Monitoring (TDM) is a useful tool for detecting nonadherence. Therefore a LC-MS/MS-method for determination of Metoprolol (MET), Amlodipine (AML), Canrenone (CAN) and Hydrochlorothiazide (HCT) was developed. METHODS: An UHPLC-MS/MS method was developed and validated for simultaneous determination of MET, AML, CAN and HCT in plasma matrix. Extraction of serum samples consisted of simple protein precipitation using acetonitrile. Stable isotope labeled analogues for each antihypertensive were obtained for internal standardization and quantitative analysis ([2H7]-MET, ([13C6]-AML, [2H4]-CAN, [13C6]-HCT). Calibrators and quality controls were prepared in plasma matrix of normal individuals. Sample preparation: protein precipitation with acetonitrile and addition of internal standard-mix. RESULTS: All analytes were eluted within a runtime of 2.5 min. Linearity experiments were demonstrated in plasma over following concentration ranges: MET: 5-750 µg/l, AML: 1-50 µg/l, CAN: 10-500 µg/l, HCT: 5-500 µg/l (R2 > 0.993). Chromatographic separation was achieved using a C18 column (50 × 2.1 mm, 1.9 µm particle size) and an isocratic elution. LC-MS/MS analyses were performed on a triple quadrupole mass spectrometer using positive and negative electrospray ionization in selected reaction monitoring (SRM) mode. Ion transitions monitored for quantitation were m/z 268.2 → 74.1 for MET, m/z 409.1 → 238.0 for AML, m/z 341.2 → 91.0 for CAN and m/z 296.0 → 205.1 for HCT. For all analytes, inter- and intra-day precision (CV, %) varied between 1.7 and 14.0 and inter- and intra-day accuracy values ranged from -2.5 to 7.1%. The lower limits of detection and quantification were: 0.08 and 0.23; 0.05 and 0.15; 2.82 and 8.54; and 0.02 and 0.05 µg/l for MET, AML, CAN and HCT, respectively. Results of stability experiments were within the required range of +/- 15%. CONCLUSIONS: Although the level of recommendation of TDM of antihypertensive drugs in patients with refractory hypertension is not yet established, the present LC-MS/MS-method can serve as an effective tool for detection of PK-alterations/nonadherence and may help to monitor antihypertensive pharmacotherapy.

ß-Blocker Dialyzability in Maintenance Hemodialysis Patients: A Randomized Clinical Trial.

BACKGROUND AND OBJECTIVES: There is a paucity of data available to describe drug dialyzability. Of the available information, most was obtained before implementation of modern hemodialysis membranes. Our study characterized dialyzability of the most commonly prescribed ß-blockers in patients undergoing high-flux hemodialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Patients on hemodialysis (n=8) were recruited to an open label, pharmacokinetic, four-way crossover trial. Single doses of atenolol, metoprolol, bisoprolol, and carvedilol were administered on separate days in random order to each patient. Plasma and dialysate drug concentrations were measured, and dialyzability was determined by the recovery clearance and arterial venous difference methods. RESULTS: Using the recovery clearance method, the dialytic clearance values for atenolol, metoprolol, bisoprolol, and carvedilol were 72, 87, 44, and 0.2 ml/min, respectively (P<0.001). Applying the arterial venous difference method, the dialytic clearance values of atenolol, metoprolol, bisoprolol, and carvedilol were 167, 114, 96, and 24 ml/min, respectively (P<0.001). CONCLUSIONS: Atenolol and metoprolol are extensively cleared by hemodialysis compared with the negligible dialytic clearance of carvedilol. Contrary to estimates of dialyzability on the basis of previous literature, our data indicate that bisoprolol is also dialyzable. This finding highlights the importance of conducting dialyzability studies to definitively characterize drug dialytic clearance.

How do different extracorporeal circulation systems affect metoprolol bioavailability in coronary artery bypass surgery patients.

PURPOSE: Cardiac surgery and conventional extracorporeal circulation (CECC) impair the bioavailability of drugs administered by mouth. It is not known whether miniaturized ECC (MECC) or off-pump surgery (OPCAB) affect the bioavailability in similar manner. We evaluated the metoprolol bioavailability in patients undergoing CABG surgery with CECC, MECC, or having OPCAB. METHODS: Thirty patients, ten in each group, aged 44-79 years, scheduled for CABG surgery were administered 50 mg metoprolol by mouth on the preoperative day at 8-10 a.m. and 8 p.m., 2 h before surgery, and thereafter daily at 8 a.m. and 8 p.m. Blood samples were collected up to 12 h after the morning dose on the preoperative day and on first and third postoperative days. Metoprolol concentration in plasma was analyzed using liquid chromatography-mass spectrometry. RESULTS: The absorption of metoprolol was markedly reduced on the first postoperative day in all three groups, but recovered to the preoperative level on the third postoperative day. The geometric means (90% confidence interval) of AUC0-12 on the first and third postoperative days versus the preoperative day were 44 (26-74)% and 109 (86-139)% in the CECC-group, 28 (16-50)% and 79 (59-105)% in the MECC-group, and 26 (12-56)% and 96 (77-119)% in the OPCAB-group, respectively. Two patients in the CECC-group and two in the MECC-group developed atrial fibrillation (AF). The bioavailability and the drug concentrations of metoprolol in patients developing AF did not differ from those who remained in sinus rhythm. CONCLUSION: The bioavailability of metoprolol by mouth was markedly reduced in the early phase after CABG with no difference between the CECC-, MECC-, and OPCAB-groups.

Development of metoprolol tartrate-loaded sustained-release pellets: effect of talc on the mechanism of drug release.

Talc is one of the most commonly used antiadherents in the coating film. However, the mechanism of influence of talc on drug release has yet to be fully understood. In this study, metoprolol tartrate (MT)-loaded Eudragit NE 30 D-coated sustained-release (SR) pellets were prepared using talc as an antiadherent in the layering and coating processes. Talc significantly reduced the stickiness of the layered or coated substrates, thus enhancing the process smoothness. Moreover, the incorporation of talc into the coating film significantly affected drug release. The water vapor permeability and drug permeability of free films increased as the concentration of talc increased. Importantly, talc had a dynamic effect on the drug release. The drug release rate of the pellets in the initial stage (within 2 h) increased with increasing talc concentrations, which exceeded the critical pigment volume concentration resulted in leaks formation in the coated film. However, subsequent swelling of the membrane and expansion of the copolymer network eliminated the influence of talc and the drug release was then controlled by the polymeric membrane. These results suggest that talc contributed to the reduction of the sticking of layered or coated substrates, and facilitated the manufacturing process and drug release properties.