Karen May

Carbamazepine regulates intestinal P‐glycoprotein and multidrug resistance protein MRP2 and influences disposition of talinolol in humans

The antiepileptic drug carbamazepine is known to be an inducer of cytochrome P450 (CYP) 3A4 after binding to the nuclear pregnane X receptor. To evaluate whether it also regulates the multidrug transporter proteins P‐glycoprotein (P‐gp) and multidrug resistance protein MRP2 in humans, duodenal expression of multidrug resistance gene MDR1 messenger ribonucleic acid (mRNA) and MRP2 mRNA, content of P‐gp and MRP2, and disposition of the nonmetabolized P‐gp substrate talinolol after intravenous (30 mg) and long‐term oral administration (100 mg for 19 days) were assessed in 7 healthy subjects (age, 23–35 years; body weight, 64–93 kg) before and after comedication of carbamazepine (600 mg for 14–18 days).

Influence of genetic polymorphisms on intestinal expression and rifampicin-type induction of ABCC2 and on bioavailability of talinolol.

Objectives To evaluate whether ABCC2 gene polymorphisms are associated with expression and/or function of the efflux pump. Methods We investigated the allele frequency of ABCC2 -24C>T, -23G>A, c.1249G>A, c.1446C>G, c.1457C>T, c.2302C>T, c.2366C>T, c.3542G>T, c.3561G>A, c.3563T>A, c.3972C>T, c.4348G>A, and 4544G>A in 374 nonrelated German healthy volunteers and determined the impact on duodenal mRNA and protein content of ABCC2. For functional analysis, the disposition of intravenously (30 mg) and orally administered talinolol (100 mg) was measured among 31 individuals. Moreover, the effects of rifampicin-type induction (600 mg, 8 days) of duodenal ABCC2 were quantified in 22 participants with regard to genetic polymorphisms. Results The allele frequencies were 18.3% (-24T), 21.1% (1249A), 1.4% (1446G), 0.1% (3542T), 4.5% (3563A), 34.2% (3972T), and 4.4% (4544A); carriers of -23G>A, 1457C>T, 2302C>T, 2366C>T, 3561G>A, and 4348G>A were not identified. The -24T allele was in strong linkage with 3972T, and 3563A with 4544A, whereas 1249A was weakly linked with other variant alleles. None of the single nucleotide polymorphisms investigated influenced significantly intestinal ABCC2 mRNA and protein content. The variant ABCC2 1249G>A (V417I), however, was associated with lower oral bioavailability (P=0.001), and increased residual clearance of intravenous talinolol (P=0.021). Intestinal ABCC2 mRNA and protein expression were upregulated by rifampicin treatment, a genetic influence could be detected in only four cases heterozygote for 3563T>A or 4544G>A. Conclusion The 1249G>A (V417I) polymorphism is obviously associated with higher activity of the intestinal transporter.

Rapid Modulation of the Organic Anion Transporting Polypeptide 2B1 (OATP2B1, SLCO2B1) Function by Protein Kinase C-mediated Internalization

Members of the organic anion transporting polypeptide (OATP) family are involved in various pharmacological, pathophysiological, and physiological processes, such as hepatic drug uptake, progress of cancer, or transport of hormones. Although variability in expression and function of OATPs has been investigated in detail, data concerning regulation are rather limited. Here, we report a novel mechanism for rapid regulation of OATP2B1 mediated by protein kinase C (PKC) resulting in significant changes of transport activity. PKC activation by the phorbol ester (phorbol 12-myristate 13-acetate, PMA) resulted in increased phosphorylation of OATP2B1 as well as reduced OATP2B1 transport activity with a decrease in Vmax of E1S uptake (288 ± 21 (control) versus 165 ± 16 pmol/min/mg of protein (PMA)). This effect was sensitive to the PKC inhibitor bisindolylmaleimide I (BIM-I). Confocal microscopy, fluorescence-based internalization assay, and live-cell imaging using green fluorescent protein-tagged OATP2B1 revealed that transport inhibition was due to internalization of the transporter. Furthermore, colocalization with LAMP-2 and chloroquine-sensitive degradation of OATP2B1 suggest that the internalized protein is targeted to a lysosomal degradation pathway. With regard to the underlying mechanism inhibition of caveolin/lipid raft-mediated endocytosis failed to prevent OATP2B1 internalization, whereas inhibition of clathrin-mediated processes blocked OATP2B1 sequestration. However, small interfering RNA-mediated clathrin knock-down affected general trafficking of OATP2B1 and resulted in intracellular accumulation in the absence of PMA. In conclusion, our data demonstrate that OATP2B1 function is regulated by PKC-mediated, clathrin-dependent internalization and followed by lysosomal degradation. Furthermore, internalization could be shown in an ex vivo placenta perfusion. Our findings represent a new, rapid mechanism in regulation of human OATPs.

Commonly used nonionic surfactants interact differently with the human efflux transporters ABCB1 (p-glycoprotein) and ABCC2 (MRP2).

The efflux transporters ABCB1 (p-glycoprotein) and ABCC2 (MRP2) play an essential role in the limitation of oral bioavailability of drugs. In the last years, pharmaceutical surfactants like cremophor® EL or polysorbate 80 have been shown to interact with ABCB1. However, the knowledge about their influence on ABCC2 is still limited. In this study, the interactions of the nonionic surfactants cremophor® EL, cremophor® RH 40, polysorbate 80, vitamin E TPGS 1000, pluronic® PE 10300 and sucrose ester L-1695 with both efflux transporters were investigated on cellular level. Cell accumulation studies and transport studies were performed using transfected MDCK II cell models. The influence of ABCC2 inhibiting surfactants on the expression level of ABCC2 was also studied. The investigations showed that cremophor® EL, vitamin E TPGS 1000 and higher concentrations of polysorbate 80 inhibit both transporters. Pluronic® PE 10300 and sucrose ester L-1695 inhibit ABCB1 but not ABCC2. Cremophor® RH 40 only shows inhibitory activity on ABCC2. During the investigated incubation period none of the inhibiting surfactants caused an alteration in ABCC2mRNA or protein expression. These findings indicate that the observed interactions are caused by specific inhibition of the transport activity of ABCC2.

Antibody-Dependent Transplacental Transfer of Malaria Blood-Stage Antigen Using a Human Ex Vivo Placental Perfusion Model

Prenatal exposure to allergens or antigens released by infections during pregnancy can stimulate an immune response or induce immunoregulatory networks in the fetus affecting susceptibility to infection and disease later in life. How antigen crosses from the maternal to fetal environment is poorly understood. One hypothesis is that transplacental antigen transfer occurs as immune complexes, via receptor-mediated transport across the syncytiotrophoblastic membrane and endothelium of vessels in fetal villi. This hypothesis has never been directly tested. Here we studied Plasmodium falciparum merozoite surface protein 1 (MSP1) that is released upon erythrocyte invasion. We found MSP1 in cord blood from a third of newborns of malaria-infected women and in >90% following treatment with acid dissociation demonstrating MSP1 immune complexes. Using an ex vivo human placental model that dually perfuses a placental cotyledon with independent maternal and fetal circuits, immune-complexed MSP1 transferred from maternal to fetal circulation. MSP1 alone or with non-immune plasma did not transfer; pre-incubation with human plasma containing anti-MSP1 was required. MSP1 bound to IgG was detected in the fetal perfusate. Laser scanning confocal microscopy demonstrated MSP1 in the fetal villous stroma, predominantly in fetal endothelial cells. MSP1 co-localized with IgG in endothelial cells, but not with placental macrophages. Thus we show, for the first time, antibody-dependent transplacental transfer of an antigen in the form of immune complexes. These studies imply frequent exposure of the fetus to certain antigens with implications for management of maternal infections during pregnancy and novel approaches to deliver vaccines or drugs to the fetus.

Role of the Multidrug Transporter Proteins ABCB1 and ABCC2 in the Diaplacental Transport of Talinolol in the Term Human Placenta

Placental syncytiotrophoblasts are known to express the efflux transporter proteins P-glycoprotein (ABCB1) and multidrug resistance-associated protein 2 (ABCC2), which are supposed to be a functional part of the human placental barrier. With advancing gestational age, expression of ABCB1 decreases progressively, whereas ABCC2 is more expressed. To evaluate to which extent they contribute to placental barrier function at term, permeability of talinolol, a substrate of both carriers, was measured using a validated human placenta perfusion model. We identified in randomized, crossover experiments a unidirectional transfer of talinolol in the fetomaternal direction because the maternofetal transfer was significantly lower (0.663 ± 0.188 versus 0.394 ± 0.067 relative to creatinine permeability, p = 0.012). Maternofetal permeability was increased by the ABCC2 inhibitor probenecid (0.59 ± 0.15 versus 0.68 ± 0.13, p = 0.028) and the nonspecific inhibitor verapamil (0.53 ± 0.09 versus 0.66 ± 0.16, p = 0.028) but was not influenced by the ABCB1 inhibitor valspodar (PSC833) (0.48 ± 0.11 versus 0.46 ± 0.09, p = 0.345). Genetic polymorphisms of ABCB1 and ABCC2 lacked significant influence on expression of the carriers and permeability of talinolol, respectively. In conclusion, maternofetal transfer of talinolol is restricted by a unidirectional process that is influenced by inhibitors of ABCC2.

Disposition and Antimuscarinic Effects of the Urinary Bladder Spasmolytics Propiverine: Influence of Dosage Forms and Circadian-Time Rhythms

Propiverine extended release is expected to be better tolerated compared to immediate release tablets because of slower drug release and reduced formation of active metabolites in the colon. CYP3A4 and ABCC2, the major variables in pharmacokinetics of propiverine, are less expressed in the colon. Therefore, disposition and pharmacodynamics of propiverine were measured in a double‐blind, double‐dummy, crossover study with administration of 15 mg immediate release 3 times daily for 7 days compared to 45 mg extended release once daily for 7 days in 24 healthy subjects. Twelve subjects also received 15 mg propiverine intravenously. Serum and urine propiverine levels were measured repeatedly following oral administration on day 7 for up to 72 hours and correlated to duodenal expression of CYP3A4, ABCB1, and ABCC2. Propiverine immediate release 3 times daily was not different to extended release once daily in areas under the serum concentration‐time curve (0–24 hours) and peak‐trough fluctuation. The areas under the serum concentration‐time curve of propiverine immediate release was circadian‐time‐dependent, with the lowest values during the night. Disposition of intravenous propiverine and propiverine immediate release administered in the night was influenced by intestinal expression of ABCC2. We concluded that oral absorption of propiverine is site‐dependent and influenced by dosage form and circadian‐time‐dependent elimination processes.

Fingerhut ein alter Hut? Eine Analyse stationärer Aufnahmen durch digitalisassoziierte unerwünschte Arzneimittelwirkungen

ZusammenfassungHintergrund:Obwohl der klinische Nutzen einer Digitalistherapie bei Herzinsuffizienz begrenzt ist, wurden in Deutschland im Jahre 2004 ca. 255 Mio. Tagesdosen Digitalisglykoside (DGs) verordnet.Methodik:Für den Zeitraum 2000–2004 analysierten die Autoren zur stationären Aufnahme führende unerwünschte Arzneimittelwirkungen (UAWs) der nationalen Pharmakovigilanzzentren, deren Zusammenhang mit einer DG-Therapie als mindestens „wahrscheinlich“ bewertet wurde.Ergebnisse:Von 3 092 Patienten mit aufnahmebedingender UAW lag bei 314 Patienten (10,2%, 244 Frauen) eine DG-assoziierte UAW vor. Patienten mit DG-assoziierter UAW waren signifikant älter und leichter als Patienten mit anderen UAWs. Die Inzidenz [95%-CI] betrug 1,9 [1,0; 3,3] pro 1 000 DG-Exponierte je Quartal. Von 296 Patienten (228 Frauen) mit oraler Digitoxintherapie erhielten 70,6% der Frauen, aber nur 29,3% der Männer eine zu hohe tägliche Dosis, d.h. > 1 μg/kg Körpergewicht. Bei Frauen fanden sich signifikant höhere körpergewichtsbezogene Digitoxintagesdosen und Digitoxinserumspiegel. Bei Patienten mit nicht erhöhten Digitoxinspiegeln waren häufig pharmakodynamische Medikamenteninteraktionen (z.B. β-Blocker) entscheidend für die UAW-Entstehung. 42,4% der DG-UAWs wurden als vermeidbar eingeschätzt.Schlussfolgerung:Die Verschreibung einer körpergewichtsadaptierten Digitoxindosis ist wesentlich für die Verhinderung vermeidbarer DG-UAWs, insbesondere bei älteren, leichten Frauen. Regelmäßige Serumspiegelkontrollen sind auch aufgrund einer möglicherweise verlängerten Halbwertszeit bei sehr alten Patienten wichtig, ebenso die Beachtung pharmakodynamischer und pharmakokinetischer Interaktionen.AbstractBackground:Although the value of digitalis glycosides in the treatment of heart failure is limited, approximately 255 million DDDs of digitalis glycosides (DGs) were prescribed in Germany in 2004.Method:The authors analyzed data from adverse drug reactions (ADRs) resulting in hospitalization in the four German Pharmacovigilance Centers (PVCs) associated with DGs between 2000 and 2004. All patients with an at least “probable” ADR were included. Results:Out of 3,092 ADR patients, in 314 patients (10.2%, 244 women) admission was caused by a DG-related ADR. Patients with DG-related ADR had a significantly lower body weight and were significantly older than patients with other ADRs. Per 1,000 patients exposed to DGs the incidence [95% CI] was calculated to 1.9 [1.0; 3.3] ADRs per 3 months exposition. Oral digitoxin was involved in 296 patients (228 women). 70.6% of women but only 29.3% of men were overdosed (> 1 μg/kg body weight per day). Women received significantly higher body weight-related digitoxin doses and had significantly higher digitoxin plasma levels than men. ADRs in patients with nonelevated digitoxin serum level were mainly caused by pharmacodynamic drug-drug interactions (e.g., β-blockers). Overall, 42.4% of the ADRs were supposed to be preventable.Conclusion:Body weight-adapted dosing of digitoxin is essential for preventing DG-ADRs, particularly in elderly women with low body weight. Beyond giving attention to pharmacodynamic and pharmakokinetic drug-drug interactions, regular measurements of digitoxin plasma concentrations are crucial accounting for the increased half-life of digitoxin in the very old.

Fingerhut – ein alter Hut?

ZusammenfassungHintergrund:Obwohl der klinische Nutzen einer Digitalistherapie bei Herzinsuffizienz begrenzt ist, wurden in Deutschland im Jahre 2004 ca. 255 Mio. Tagesdosen Digitalisglykoside (DGs) verordnet.Methodik:Für den Zeitraum 2000–2004 analysierten die Autoren zur stationären Aufnahme führende unerwünschte Arzneimittelwirkungen (UAWs) der nationalen Pharmakovigilanzzentren, deren Zusammenhang mit einer DG-Therapie als mindestens „wahrscheinlich“ bewertet wurde.Ergebnisse:Von 3 092 Patienten mit aufnahmebedingender UAW lag bei 314 Patienten (10,2%, 244 Frauen) eine DG-assoziierte UAW vor. Patienten mit DG-assoziierter UAW waren signifikant älter und leichter als Patienten mit anderen UAWs. Die Inzidenz [95%-CI] betrug 1,9 [1,0; 3,3] pro 1 000 DG-Exponierte je Quartal. Von 296 Patienten (228 Frauen) mit oraler Digitoxintherapie erhielten 70,6% der Frauen, aber nur 29,3% der Männer eine zu hohe tägliche Dosis, d.h. > 1 μg/kg Körpergewicht. Bei Frauen fanden sich signifikant höhere körpergewichtsbezogene Digitoxintagesdosen und Digitoxinserumspiegel. Bei Patienten mit nicht erhöhten Digitoxinspiegeln waren häufig pharmakodynamische Medikamenteninteraktionen (z.B. β-Blocker) entscheidend für die UAW-Entstehung. 42,4% der DG-UAWs wurden als vermeidbar eingeschätzt.Schlussfolgerung:Die Verschreibung einer körpergewichtsadaptierten Digitoxindosis ist wesentlich für die Verhinderung vermeidbarer DG-UAWs, insbesondere bei älteren, leichten Frauen. Regelmäßige Serumspiegelkontrollen sind auch aufgrund einer möglicherweise verlängerten Halbwertszeit bei sehr alten Patienten wichtig, ebenso die Beachtung pharmakodynamischer und pharmakokinetischer Interaktionen.AbstractBackground:Although the value of digitalis glycosides in the treatment of heart failure is limited, approximately 255 million DDDs of digitalis glycosides (DGs) were prescribed in Germany in 2004.Method:The authors analyzed data from adverse drug reactions (ADRs) resulting in hospitalization in the four German Pharmacovigilance Centers (PVCs) associated with DGs between 2000 and 2004. All patients with an at least “probable” ADR were included. Results:Out of 3,092 ADR patients, in 314 patients (10.2%, 244 women) admission was caused by a DG-related ADR. Patients with DG-related ADR had a significantly lower body weight and were significantly older than patients with other ADRs. Per 1,000 patients exposed to DGs the incidence [95% CI] was calculated to 1.9 [1.0; 3.3] ADRs per 3 months exposition. Oral digitoxin was involved in 296 patients (228 women). 70.6% of women but only 29.3% of men were overdosed (> 1 μg/kg body weight per day). Women received significantly higher body weight-related digitoxin doses and had significantly higher digitoxin plasma levels than men. ADRs in patients with nonelevated digitoxin serum level were mainly caused by pharmacodynamic drug-drug interactions (e.g., β-blockers). Overall, 42.4% of the ADRs were supposed to be preventable.Conclusion:Body weight-adapted dosing of digitoxin is essential for preventing DG-ADRs, particularly in elderly women with low body weight. Beyond giving attention to pharmacodynamic and pharmakokinetic drug-drug interactions, regular measurements of digitoxin plasma concentrations are crucial accounting for the increased half-life of digitoxin in the very old.

Fingerhut – ein alter Hut?@@@Analysis of Hospital Admissions Associated with Digitalis Glycosides: Eine Analyse stationärer Aufnahmen durch digitalisassoziierte unerwünschte Arzneimittelwirkungen

ZusammenfassungHintergrund:Obwohl der klinische Nutzen einer Digitalistherapie bei Herzinsuffizienz begrenzt ist, wurden in Deutschland im Jahre 2004 ca. 255 Mio. Tagesdosen Digitalisglykoside (DGs) verordnet.Methodik:Für den Zeitraum 2000–2004 analysierten die Autoren zur stationären Aufnahme führende unerwünschte Arzneimittelwirkungen (UAWs) der nationalen Pharmakovigilanzzentren, deren Zusammenhang mit einer DG-Therapie als mindestens „wahrscheinlich“ bewertet wurde.Ergebnisse:Von 3 092 Patienten mit aufnahmebedingender UAW lag bei 314 Patienten (10,2%, 244 Frauen) eine DG-assoziierte UAW vor. Patienten mit DG-assoziierter UAW waren signifikant älter und leichter als Patienten mit anderen UAWs. Die Inzidenz [95%-CI] betrug 1,9 [1,0; 3,3] pro 1 000 DG-Exponierte je Quartal. Von 296 Patienten (228 Frauen) mit oraler Digitoxintherapie erhielten 70,6% der Frauen, aber nur 29,3% der Männer eine zu hohe tägliche Dosis, d.h. > 1 μg/kg Körpergewicht. Bei Frauen fanden sich signifikant höhere körpergewichtsbezogene Digitoxintagesdosen und Digitoxinserumspiegel. Bei Patienten mit nicht erhöhten Digitoxinspiegeln waren häufig pharmakodynamische Medikamenteninteraktionen (z.B. β-Blocker) entscheidend für die UAW-Entstehung. 42,4% der DG-UAWs wurden als vermeidbar eingeschätzt.Schlussfolgerung:Die Verschreibung einer körpergewichtsadaptierten Digitoxindosis ist wesentlich für die Verhinderung vermeidbarer DG-UAWs, insbesondere bei älteren, leichten Frauen. Regelmäßige Serumspiegelkontrollen sind auch aufgrund einer möglicherweise verlängerten Halbwertszeit bei sehr alten Patienten wichtig, ebenso die Beachtung pharmakodynamischer und pharmakokinetischer Interaktionen.AbstractBackground:Although the value of digitalis glycosides in the treatment of heart failure is limited, approximately 255 million DDDs of digitalis glycosides (DGs) were prescribed in Germany in 2004.Method:The authors analyzed data from adverse drug reactions (ADRs) resulting in hospitalization in the four German Pharmacovigilance Centers (PVCs) associated with DGs between 2000 and 2004. All patients with an at least “probable” ADR were included. Results:Out of 3,092 ADR patients, in 314 patients (10.2%, 244 women) admission was caused by a DG-related ADR. Patients with DG-related ADR had a significantly lower body weight and were significantly older than patients with other ADRs. Per 1,000 patients exposed to DGs the incidence [95% CI] was calculated to 1.9 [1.0; 3.3] ADRs per 3 months exposition. Oral digitoxin was involved in 296 patients (228 women). 70.6% of women but only 29.3% of men were overdosed (> 1 μg/kg body weight per day). Women received significantly higher body weight-related digitoxin doses and had significantly higher digitoxin plasma levels than men. ADRs in patients with nonelevated digitoxin serum level were mainly caused by pharmacodynamic drug-drug interactions (e.g., β-blockers). Overall, 42.4% of the ADRs were supposed to be preventable.Conclusion:Body weight-adapted dosing of digitoxin is essential for preventing DG-ADRs, particularly in elderly women with low body weight. Beyond giving attention to pharmacodynamic and pharmakokinetic drug-drug interactions, regular measurements of digitoxin plasma concentrations are crucial accounting for the increased half-life of digitoxin in the very old.