Determination of the contamination by azole antimycotics in hospital and house sewage - a pilot project for the city of Dresden.

Medicininal compounds and their metabolites are known to end up in sewerage and may slip through the cleaning process. Azole antimycotics are frequently used in hospitals, in particular for patients with cancer or immunosuppression. The aim of the study was to determine whether measurable azole antimycotic concentrations were introducted in the sewarage drain of an acute care hospital with special interest in oncology and hematology and the extent of removal of antimycotics by the sewerage treatment plant. For this, the concentrations of three commonly used azole antimycotics were measured in the effluent of the sewerage drain at the University Hospital Dresden, as well as in the influent and effluent of the main sewerage treatment plant of the city. To extrapolate the theoretical influent to the sewerage treatment plant, prescription from the regio`s main health insurance the AOK Sachsen and the hospital consumption data were used. Measurable concentrations were obtained for fluconazole and ketoconazole in the influent and effluent of the sewerage treatment plant. Voriconazole's concentrations were under the lower limit of quantification. To determine the azole clearance of the treatment plant a sludge sample was investigated. Sufficient clearance was detected for ketoconazole but not for fluconazole. The consumption and prescription rates were collected and correlated with the measured concentrations. In result, only fluconazole's concentrations provided a good match with the prescription and consumption data.

Efficacy of BRAF/MEK-inhibitor therapy for epithelioid glioblastoma with a novel BRAFV600 mutation.

Epithelioid glioblastoma (eGB), a very aggressive and rare brain tumour, is associated with a dismal median overall survival. Effective therapies for patients with eGB, particularly with leptomeningeal dissemination, are still lacking. Here, we describe a case of a 25-year-old male diagnosed with an intramedullary cervical tumour with subsequent leptomeningeal disease. Histopathology identified a highly necrotising, epithelioid-type tumour with high cell density, most compatible with the diagnosis of an eGB. DNA analysis revealed an unprecedented B-Raf protooncogene, serine/threonine kinase (BRAF) gene variant in exon 15 (ENST00000288602.6, c.1799_1810delinsATG, p.(V600_W604delinsDG)), triggering activation of the mitogen-activated protein kinase (MAPK) pathway. Consequently, we initiated MAPK inhibitor (MAPKi) therapy, utilizing a combination of BRAF and mitogen-activated protein kinase kinase (MEK) inhibitors. Liquid chromatography-tandem mass spectrometry analysis confirmed the drugs' presence in the patient's cerebrospinal fluid, indicating their capacity to cross the blood-brain barrier. Remarkably, the patient responded very well to therapy and transitioned from a near-comatose state to significantly improved health, sustained for over three months. This study highlights that MAPKi, particularly targeted towards novel BRAFV600 mutations, might offer promising advancements in eGB treatment strategies.

Meeting the challenge of interpreting high-resolution single nucleotide polymorphism array data in prenatal diagnosis: does increased diagnostic power outweigh the dilemma of rare variants?

OBJECTIVE: Several studies have already shown the superiority of chromosomal microarray analysis (CMA) compared with conventional karyotyping for prenatal investigation of fetal ultrasound abnormality. This study used very high-resolution single nucleotide polymorphism (SNP) arrays to determine the impact on detection rates of all clinical categories of copy number variations (CNVs), and address the issue of interpreting and communicating findings of uncertain or unknown clinical significance, which are to be expected at higher frequency when using very high-resolution CMA. DESIGN: Prospective validation study. SETTING: Tertiary clinical genetics centre. POPULATION: Women referred for further investigation of fetal ultrasound anomaly. METHODS: We prospectively tested 104 prenatal samples using both conventional karyotyping and high-resolution arrays. MAIN OUTCOME MEASURES: The detection rates for each clinical category of CNV. RESULTS: Unequivocal pathogenic CNVs were found in six cases, including one with uniparental disomy (paternal UPD 14). A further four cases had a 'likely pathogenic' finding. Overall, CMA improved the detection of 'pathogenic' and 'likely pathogenic' abnormalities from 2.9% (3/104) to 9.6% (10/104). CNVs of 'unknown' clinical significance that presented interpretational difficulties beyond results from parental investigations were detected in 6.7% (7/104) of samples. CONCLUSIONS: Increased detection sensitivity appears to be the main benefit of high-resolution CMA. Despite this, in this cohort there was no significant benefit in terms of improving detection of small pathogenic CNVs. A potential disadvantage is the high detection rate of CNVs of 'unknown' clinical significance. These findings emphasise the importance of establishing an evidence-based policy for the interpretation and reporting of CNVs, and the need to provide appropriate pre- and post-test counselling.

Pathogenic aberrations revealed exclusively by single nucleotide polymorphism (SNP) genotyping data in 5000 samples tested by molecular karyotyping.

BACKGROUND: Several recent studies have demonstrated the use of single nucleotide polymorphism (SNP) arrays for the investigation of intellectual disability, developmental delay, autism or congenital abnormalities. In addition to LogR 'copy number' data, these arrays provide SNP genotyping data for gene level autozygosity mapping, estimating low levels of mosaicism, assessing long continuous stretches of homozygosity (LCSH), detection of uniparental disomy, and 'autozygous' regions. However, there remains little specific information on the clinical utility of this genotyping data. METHODS: Molecular karyotyping, using SNP array, was performed on 5000 clinical samples. RESULTS: Clinically significant 'LogR neutral' genotyping abnormalities were detected in 0.5% of cases. Among these were a single case of chimerism, 12 cases with low level chromosome mosaicism, and 11 cases with an LCSH associated with uniparental disomy. In addition, the genotyping data revealed several LCSH associated with clinically relevant 'recessive type' genetic defects. CONCLUSIONS: These results demonstrate the utility of SNP genotyping data for detection of clinically significant abnormalities, including chimerism/mosaicism and recessive Mendelian disorders associated with autozygosity. The incidence of clinically significant low level mosaicism inferred from these cases suggests that this has hitherto been underestimated and chromosome mosaicism frequently occurs in the absence of indicative clinical features. The growing appreciation among clinicians and demand for SNP genotyping data poses significant challenges for the interpretation of LCSH, especially where there is no detailed phenotypic description to direct laboratory analysis. Finally, reporting of unexpected or hidden consanguinity revealed by SNP array analysis raises potential ethical and legal issues.

Simultaneous determination of drugs in human autopsy material using phase-optimized liquid chromatography.

In legal medicine in many cases drugs are detected in autopsy material without connection to the cause of death, and until now no further investigations have taken place. In our study more than 50 drugs were measured directly in several compartments. The deceased had received continual therapeutic treatment, treatment during an operation or an unsuccessful emergency therapy. Liquid-liquid extraction and an LC-MS/MS method were developed for the determination of these drug concentrations. When measuring many transitions in a biological matrix, two problems should be excluded: ion suppression and too few measurement points per peak. A relatively short operation time and sufficient separation were achieved by column, eluent and gradient optimization with POPLC (phase-optimized liquid chromatography). Various autopsy materials from about 170 cases were investigated. In particular, in nine cases with four or more simultaneously determined drugs, their distribution in the compartments is very interesting for pharmacokinetic examinations. The distribution patterns of the drugs in the compartments of one individual deceased were compared. This meant that the great differences between subjects that are normally encountered these studies could be excluded. Measurements of drug concentrations in human autopsy material deepens knowledge of the respective drugs' pharmacokinetics.

Distribution of metoprolol in human autopsy material.

In forensic medicine autopsy material is primarily investigated to find out the cause of death. But the results of corresponding toxicology measurements often involve more information. With screening methods drugs were detected not being related to the cause of death. Liquid/liquid extraction and LC/MS/MS methods were used for the determination of drug concentrations. In seven cases metoprolol could be determined in different autopsy materials. In all cases the dosage of the drug was unknown. In cases with oral application probably the patients took a normal customary continuous dosage. Intoxication with metoprolol could be excluded in all cases. The concentrations of metoprolol in blood were all in the therapeutic range. The time between oral intake and death was unknown. Therefore and because of the low number of cases statistic calculations were not meaningful and an individual case study was necessary. In three cases the highest concentration of metoprolol was found in the liver. Probably, metoprolol was taken shortly before the person died. In the other cases the highest concentration of metoprolol was found in urine. This means the elimination process of the drug predominated at the time of death. In all cases the concentrations of metoprolol were similar in the compartments heart blood, venous blood and brain. In this study it was possible to measure the distribution of metoprolol in human directly in several compartments. Measurement of drug concentrations in human autopsy material deepen the knowledge of its pharmacokinetics.

Prednisolone vs. ciclosporin for severe adult eczema. An investigator-initiated double-blind placebo-controlled multicentre trial.

BACKGROUND: Patients with severe eczema frequently receive systemic glucocorticosteroids. The efficacy of prednisolone and other steroids, however, has never been evaluated appropriately. A meta-analysis indicated that ciclosporin is the best evaluated systemic treatment for eczema. OBJECTIVES: To investigate the comparative efficacy of prednisolone and ciclosporin for severe eczema. METHODS: In an investigator-initiated double-blind randomized multicentre trial, adults with severe eczema (objective SCORAD > or = 40 and Dermatology Life Quality Index > or = 10) were randomly allocated to receive prednisolone (initial dose 0.5-0.8 mg kg(-1) daily) for 2 weeks followed by placebo for 4 weeks or ciclosporin (2.7-4.0 mg kg(-1) daily) for 6 weeks and followed for another 12 weeks. Concomitant treatment included a moderately potent topical steroid, emollients, and continuation of antihistamines. Primary endpoint was the proportion of patients with stable remission, i.e. > or = 50% SCORAD improvement under active treatment and no flare (> or = 75% of baseline SCORAD) during follow-up. Sample size calculation indicated that 66 patients were needed to see clinically relevant differences between groups. Analysis was by intention-to-treat (ClinicalTrials.gov Identifier: NCT00445081). RESULTS: Because of unexpectedly high numbers of withdrawals due to significant exacerbations of eczema (n = 15/38) an independent data monitoring and safety board proposed early study termination. Thirty-eight patients were randomized and analysed. Stable remission was achieved in one of 21 patients receiving prednisolone compared with six of 17 patients treated with ciclosporin (P = 0.031). CONCLUSIONS: Ciclosporin is significantly more efficacious than prednisolone for severe adult eczema. Despite its frequent use in daily practice, prednisolone is not recommended to induce stable remission of eczema.

Successful resuscitation following ropivacaine-induced systemic toxicity in a neonate.

A 5-week-old preterm infant was scheduled for inguinal hernia repair. Following induction of general anaesthesia, 10 mg.kg(-1) ropivacaine was injected, accidently, into the caudal space. The infant developed cardiac depression with bradycardia (minimum heart rate 50 beats.min(-1) ), elevated T waves and widening of QRS complexes. Resuscitation by means of external chest compression, intravenous adrenaline and fluid administration was successful. Ropivacaine serum concentrations were obtained at three time points yielding a peak level of 6 µg.ml(-1) 20 min after caudal injection.

Determination of denaverine and its metabolites in urine samples by liquid chromatography-tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method was developed for the determination of the neurotropic-musculotropic spasmolytic agent denaverine and five of its metabolites in urine. In a first step beta-glucuronidase was used to cleave glucuronides in the human urine. After that samples containing denaverine and its phase I metabolites were extracted and cleaned up using an automated solid phase extraction method. An external calibration was used. The analytes were measured employing the multiple reaction-monitoring mode (MRM). The linear dynamic range for denaverine and its five metabolites determination was demonstrated from lower limit of quantification (8.0 ng/ml) to at least 500 ng/ml. The presented method is suitable for pharmacokinetic or toxicokinetic studies. With the help of reference substances some additional potential metabolites could be excluded in the urine samples. To look for additional unknown metabolites the LC-MS-MS system operated on one hand in the precursor ion mode using typical product ions of denaverine and of its metabolites and on the other hand in the product ion mode using postulated protonated molecules [M+H](+). With the help of the chromatographic behaviour and typical fragment ions of the unknown metabolites it was possible to elucidate their structures. Nine until now unknown metabolites were found in the urine samples. However, without reference substances a quantification of these analytes was not possible.

Characterization of vascular reactivity in dorsal hand veins after oral rosiglitazone treatment in healthy subjects.

OBJECTIVE: In clinical studies with diabetic patients thiazolidinediones have been shown to restore abnormal vascular function which might be attributed to improved blood sugar control or to restoration of vascular endothelium and smooth muscle responsiveness. The present study was undertaken to investigate whether rosiglitazone modulates vascular responsiveness to different vasoactive agents and exerts renin-angiotensin-system (RAS)-inhibiting properties in healthy subjects in vivo. METHODS: 24 healthy male subjects were randomized to receive either rosiglitazone or placebo. Venoconstrictor responses to angiotensin II (Ang II) and phenylephrine, and endothelium-dependent response to histamine and insulin, and endothelium-independent response to glyceroltrinitrate were compared using the dorsal hand vein compliance method. Effects on the RAS were investigated by plasma level determinations of Ang II and angiotensin-(1-7). Treatment effects on the systemic arterial system were investigated by standardized pulse-wave-analysis. RESULTS: Rosiglitazone significantly inhibited venoconstrictor responses to Ang II by 19% (-70% vs. -51% constriction, p = 0.034) and in the presence of rosiglitazone the ED80 for phenylephrine was increased (ED80: 317 A+/- 86 ng vs. 531 A+/- 102 ng; p = 0.010). Rosiglitazone treatment was without effect on endothelium-dependent dilation, blood pressure, pulse-wave-velocity and plasma angiotensin peptide levels. CONCLUSIONS: The data of the present study in veins of healthy subjects are consistent with data from in vitro and animal studies supporting a direct effect of rosiglitazone on venous tone by modulation of the vascular smooth muscle response via AT1-receptor-downregulation.

Induction of intestinal P-glycoprotein by St John's wort reduces the oral bioavailability of talinolol.

St John's wort (SJW) is known to induce cytochrome P450 (CYP) 3A4 and P-glycoprotein through pregnane X-receptor activation. Our study evaluated the effects of long-term SJW administration on oral and intravenous pharmacokinetics of the nonmetabolized in vivo probe of P-glycoprotein, talinolol, in relation to intestinal P-glycoprotein expression. In a controlled, randomized study (N=9), the pharmacokinetics of oral (50 mg) and intravenous talinolol (30 mg) was determined before and after 12 days SJW (900 mg daily, Jarsin 300). Duodenal biopsies were taken and MDR1 genotypes assessed. SJW reduced the oral talinolol bioavailability by 25% (P=0.049) compared with water control. A 93% increase in oral clearance (P=0.177) and a 31% reduction in area under the serum concentration time curve (AUC; P=0.030) were observed. Renal and nonrenal clearance (CLNR), elimination half-life, peak serum drug concentration (Cmax), and time to reach Cmax were not significantly altered. After intravenous talinolol, SJW affected only CLNR (35% increase compared with water, P=0.006). SJW increased MDR1 messenger ribonucleic acid (mRNA) as well as P-glycoprotein levels in the duodenal mucosa. Subjects with the combined MDR1 genotype comprising 1236C>T, 2677G>T/A, and 3435C>T polymorphisms had lower intestinal MDR1 mRNA levels and displayed an attenuated inductive response to SJW as assessed by talinolol disposition. Long-term SJW decreased talinolol AUC with a corresponding increase in intestinal MDR1 expression, suggesting that SJW has a major inductive effect on intestinal P-glycoprotein. Interestingly, the magnitude of induction appeared to be affected by MDR1 genotype.

Determination of propiverine and its metabolites in rat samples by liquid chromatography-tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method was developed and validated for the determination of the anticholinergic and antimuscarinc drug propiverine and eight of its metabolites in serum, urine, faeces and different tissue samples of rats. Samples containing propiverine and its metabolites in serum and urine and in the supernatants of faeces and tissue homogenates were extracted and cleaned up using an automated solid phase extraction (SPE) method. An external calibration was used. The analytes were measured employing the multiple reaction monitoring mode (MRM). A sufficient response over the range of 10-1000 ng/ml was demonstrated. The lower limit of quantification of the nine substances was 10 ng/ml. The presented method is suitable for pharmacokinetic or toxicokinetic studies. To look for additional unknown metabolites, the LC-MS-MS system operated in the precursor ion mode using typical product ions of propiverine and of its metabolites. With the help of the chromatographic behaviour and typical fragment ions of the unknown metabolites, it was possible to elucidate their structure. Five until now unknown metabolites were found in the urine and faeces samples. However, without reference substances, a quantification of these analytes was not possible.

Prednisolone concentration in the cochlea of patients with perilymph fistula.

After iv administration of 200 mg prednisolone in patients with perilymph fistula, concentrations of the drug in the cochlea were determined. A specially adapted LC method was used for analysis. Mean concentrations of prednisolone in the perilymphe reached 95 ng/ml after 15-25 min, and 338 ng/ml after 30-45 min. The values reached 8 and 41% of the corresponding serum concentrations, respectively.

Simultaneous determination of bupivacaine, mepivacain, prilocaine and ropivacain in human serum by liquid chromatography-tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method with a rapid and simple sample preparation was developed and validated for the simultaneous determination of the local anesthetics bupivacaine, mepivacaine, prilocaine and ropivacaine in human serum. An external calibration was used. The mass spectrometer was operated in the multiple reaction monitoring mode. A good quadratic response over the range of 1.0-200.0 ng/ml was demonstrated. The accuracy for bupivacaine ranged from 93.2 to 105.7%, for mepivacaine from 96.2 to 104.3%, for prilocaine from 94.6 to 105.7% and for ropivacaine from 94.3 to 104.0%, respectively. The limit of quantification was 1.0 ng/ml for all substances. This method is suitable for pharmacokinetic studies.

Intestinal secretion of intravenous talinolol is inhibited by luminal R-verapamil.

OBJECTIVE: To examine the secretion of the beta1-adrenergic receptor antagonist talinolol into the small intestine during its intravenous administration and to show the relevance of the P-glycoprotein-modulating drug verapamil for this secretory transport mechanism in humans. METHODS: In six healthy volunteers the intestinal steady-state perfusion technique (triple lumen tubing system) was used for measuring the appearance of talinolol within the small intestine while the drug was infused intravenously. During four of the seven perfusions performed, the perfusion fluid was changed from a verapamil-free solution and talinolol appearance was measured while a R-verapamil-containing solution (565 micromol/L) was perfused. RESULTS: Talinolol was transported into the intestinal lumen up to a concentration gradient between lumen and blood of about 5.5:1. While perfusing the small intestine with a verapamil-free solution, the intestinal secretion rate of talinolol ranged from 1.94 to 6.62 microg/min per 30 cm length of the intestine (median values). Perfusion of a R-verapamil-containing perfusion fluid resulted in lower secretion rates (0.59 to 3.71 microg/30 cm x min), corresponding to 29% to 56% of the values obtained without verapamil supplied intraluminally. CONCLUSION: Intravenously administered talinolol is actively secreted into the human small intestine. This secretion is reduced by the intraluminal supply of the P-glycoprotein modulating drug R-verapamil. This gives further rationale for P-glycoprotein-mediated intestinal drug secretion as a cause for incomplete oral bioavailability and for drug interactions during intestinal absorption.

Physostigmine reversal of midazolam-induced electroencephalographic changes in healthy subjects.

OBJECTIVE: Midazolam is a water-soluble benzodiazepine. Flumazenil is a potent antagonist of midazolam-induced sedation. Physostigmine has also been shown to reverse benzodiazepine sedation in anecdotal reports. The aim of this study was to quantitatively characterize the reversal of midazolam-induced changes in electroencephalogram (EEG) by physostigmine compared to flumazenil and placebo. METHODS: Twelve healthy male subjects received 5 mg midazolam as an intravenous infusion over 15 minutes. Fifteen minutes after the end of infusion, single doses of either 0.4 mg flumazenil, 0.5 mg physostigmine, or placebo (physiologic saline solution) were administered as intravenous injections in a randomized crossover fashion. Midazolam serum concentrations were measured using liquid chromatography-tandem mass spectrometry. The time from the start of injection until awakening was noted and the EEG was measured. RESULTS: Four subjects were excluded from further pharmacokinetic and pharmacodynamic analysis because no midazolam-induced changes on EEG alpha power could be observed in each of the three study periods. The pharmacokinetics of midazolam were not influenced by flumazenil or physostigmine. Midazolam induced a decrease in EEG alpha power (7.50 to 11.25 Hz) compared with baseline (P < .05). After injection of flumazenil and physostigmine, an increase in EEG alpha power was observed, whereas placebo did not affect alpha power. Subjects opened their eyes 25.2 +/- 1.1 minutes after the placebo injection was begun, whereas subjects awoke after 6.2 +/- 2.7 minutes and 15.4 +/- 3.4 minutes after they received flumazenil and physostigmine, respectively (mean +/- SEM; P < .001). CONCLUSION: Physostigmine and flumazenil antagonized midazolam-induced sedation. This suggests that a reversible central anticholinergic mechanism may be involved in the sedative action of midazolam.

Direct demonstration of small intestinal secretion and site-dependent absorption of the beta-blocker talinolol in humans.

OBJECTIVE: To examine the relevance of site-dependent small intestinal absorption for incomplete intestinal absorption of the poorly metabolized beta 1-adrenergic receptor antagonist talinolol. METHODS: The intestinal steady-state perfusion technique (triple lumen tubing system with a 30 cm test segment) for intraluminal measurements was combined with simultaneous determination of talinolol serum concentrations. Dissolved talinolol was perfused over 160 minutes into different parts of the small intestine. The middle of the test segment was located between 25 and 235 cm beyond the teeth. Each of the six healthy subjects was studied twice with a proximal and a more distal site of perfusion to allow for comparisons within an individual subject. RESULTS: The area under the curve for serum concentrations from 0 to 480 minutes [AUC(0-480 min)] and the maximum serum concentration after distal perfusions corresponded to only 15% to 73% and 7% to 90% of the proximal values, respectively. AUC decreased with increasing distance from the teeth. The mean amount of talinolol absorbed from the test segment per unit time (intestinal transport rate) corresponds to only one-tenth of the amount of drug offered to the test segment (perfusion rate). There was a direct correlation between the perfusion rate of talinolol and its transport rate for both regions and in all subjects investigated. However, to achieve the same transport rate in the distal region a higher perfusion rate is required, compared to the proximal small intestine. At perfusion rates lower than 600 micrograms/min, net secretion of talinolol into the intestinal lumen occurred against a steep concentration gradient blood: lumen of about 1:4200. CONCLUSION: Talinolol oral bioavailability of 55% is due to a low absorption rate and a decrease of absorption capabilities along the small intestine. Net absorption of talinolol is reduced by the involvement of active intestinal secretion.

Unexpected effect of verapamil on oral bioavailability of the beta-blocker talinolol in humans.

PURPOSE: To quantitate the effect of verapamil administered orally, a calcium channel blocker and potent inhibitor of P-glycoprotein on oral pharmacokinetics of the beta1-adrenergic receptor antagonist talinolol, a substrate of P-glycoprotein. SUBJECTS AND METHODS: In a randomized, crossover placebo-controlled study, oral pharmacokinetics of talinolol (50 mg) after concomitant administration of single doses of R-verapamil (120 mg) or placebo were investigated in 9 healthy volunteers. Concentrations of talinolol, verapamil, and its main metabolite norverapamil were measured in serum with HPLC. Concentrations of talinolol were also measured in urine by HPLC. Standard pharmacokinetic parameters were calculated with noncompartmental procedures. RESULTS: The area under the concentration-time curve for talinolol from 0 to 24 hours was significantly decreased after R-verapamil versus placebo (721+/-231 ng x h x mL(-1) versus 945+/-188 ng x h x mL(-1); P < .01). Maximum serum concentration of talinolol was reached significantly earlier after R-verapamil compared with placebo (P < .05). Coadministration of R-verapamil did not affect the renal clearance or half-life of talinolol. Serum pharmacokinetics are paralleled by the results derived from urine concentrations of talinolol. CONCLUSION: This is the first study to show a decreased oral bioavailability of a P-glycoprotein substrate (talinolol) in humans as a result of coadministration of verapamil. This effect is assumed to be caused by changes of the intestinal net absorption of talinolol because its renal clearance remains unaffected by administration of R-verapamil. This unexpected effect of R-verapamil is most likely dose dependent as a result of an interplay between intestinal P-glycoprotein and gut metabolism.

Oral bioavailability of digoxin is enhanced by talinolol: evidence for involvement of intestinal P-glycoprotein.

OBJECTIVE: Recent data indicated that disposition of oral digoxin is modulated by intestinal P-glycoprotein. The cardioselective beta-blocker talinolol has been described to be secreted by way of P-glycoprotein into the lumen of the gastrointestinal tract after oral and intravenous administration. We therefore hypothesized that coadministration of digoxin and talinolol may lead to a drug-drug interaction based on a competition for intestinal P-glycoprotein. METHODS: Pharmacokinetics of digoxin (0.5 mg orally), talinolol (30 mg intravenously and 100 mg orally), and digoxin plus talinolol orally, as well as digoxin plus talinolol intravenously, were assessed in five male and five female healthy volunteers (age range, 23 to 30 years; body weight, 60 to 95 kg) in a changeover study with at least a 7-day washout period. Digoxin and talinolol were analyzed by fluorescence polarization immunoassay and HPLC, respectively. RESULTS: Oral coadministration of 100 mg talinolol increased the area under the concentration-time curve (AUC) from 0 to 6 hours and the AUC from 0 to 72 hours of digoxin significantly by 18% and 23%, respectively (5.85+/-1.49 versus 7.22+/-1.29 ng x h/mL and 23.0+/-3.3 versus 27.1+/-3.7 ng x h/mL, for both P<.05) and the maximum serum levels by 45%. Renal clearance and half-life of digoxin remained unchanged. Coinfusion of 30 mg talinolol with oral digoxin had no significant effects on digoxin pharmacokinetics. Digoxin did not affect the disposition of talinolol after both oral and intravenous administration. CONCLUSION: We observed a significantly increased bioavailability of digoxin with oral coadministration of talinolol, which is most likely caused by competition for intestinal P-glycoprotein.

Induction of P-glycoprotein by rifampin increases intestinal secretion of talinolol in human beings: a new type of drug/drug interaction.

BACKGROUND: P-Glycoprotein is an efflux pump in many epithelial cells with excretory function. It has been demonstrated that rifampin (INN, rifampicin) induces P-glycoprotein, particularly in the gut wall. We therefore hypothesized that rifampin affects pharmacokinetics of the P-glycoprotein substrate talinolol, a beta1-blocker without appreciable metabolic disposition but intense intestinal secretion in human beings. METHODS: Pharmacokinetics of talinolol (a single dose of 30 mg administered intravenously or 100 mg administered orally for 7 days) and duodenal expression of the MDR1 gene product P-glycoprotein as assessed by reverse transcriptase-polymerase chain reaction of the MDR1-messenger ribonucleic acid, by immunohistochemistry and Western blot analysis were analyzed before and after coadministration of rifampin (600 mg per day for 9 days) in 8 male healthy volunteers (age 22 to 26 years). RESULTS: During rifampin treatment, the areas under the curve of intravenous and oral talinolol were significantly lower (21% and 35%; P < .05). Treatment with rifampin resulted in a significantly increased expression of duodenal P-glycoprotein content 4.2-fold (2.9, 6.51) (Western blot) and messenger RNA was increased in six of the eight volunteers. P-Glycoprotein expression in biopsy specimens of gut mucosa correlated significantly with the systemic clearance of intravenous talinolol (rs = 0.74; P < .001). CONCLUSIONS: Rifampin induces P-glycoprotein-mediated excretion of talinolol predominantly in the gut wall. Moreover, clearance of talinolol from the blood into the lumen of the gastrointestinal tract may be predicted by the individual intestinal P-glycoprotein expression. Thus we describe a new type of steady-state drug interaction affecting compounds that are subject to transport rather than metabolism.