Pharmacokinetic Drug-Drug Interactions Between Trospium Chloride and Ranitidine Substrates of Organic Cation Transporters in Healthy Human Subjects.

Trospium chloride, a muscarinic receptor blocker, is poorly absorbed with different rates from areas in the jejunum and the cecum/ascending colon. To evaluate whether organic cation transporter (OCT) 1, OCT2 and multidrug and toxin extrusion (MATE) 1 and MATE2-K are involved in pharmacokinetics, competitions with ranitidine, a probe inhibitor of the cation transporters, were evaluated in transfected HEK293 cells. Furthermore, a drug interaction study with trospium chloride after intravenous (2 mg) and oral dosing (30 mg) plus ranitidine (300 mg) was performed in 12 healthy subjects and evaluated by noncompartmental analysis and population pharmacokinetic modeling. Ranitidine inhibited OCT1, OCT2, MATE1, and MATE2-K with half maximal inhibitory concentration values of 186 ± 25 µM, 482 ± 105 µM, 134 ± 37 µM, and 35 ± 11 µM, respectively. In contrast to our hypothesis, coadministration of ranitidine did not significantly decrease oral absorption of trospium. Instead, renal clearance was lowered by ∼15% (530 ± 99 vs 460 ± 120 mL/min; P < .05). It is possible that ranitidine was not available in competitive concentrations at the major colonic absorption site, as the inhibitor is absorbed in the small intestine and undergoes degradation by microbiota. The renal effects apparently result from inhibition of MATE1 and/or MATE2-K by ranitidine as predicted by in vitro to in vivo extrapolation. However, all pharmacokinetic changes were not of clinical relevance for the drug with highly variable pharmacokinetics. Intravenous trospium significantly lowered mean absorption time and relative bioavailability of ranitidine, which was most likely caused by muscarinic receptor blocking effects on intestinal motility and water turnover.

Ocular safety of propiverine hydrochloride in elderly patients with primary open- and narrow-angle glaucoma
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BACKGROUND: Propiverine hydrochloride (P4) is an antimuscarinic drug used in overactive bladder syndrome. METHODS: Two studies were performed: one in 24 patients with open-angle glaucoma (OAG) treated with topical ß-blockers, one in 24 patients with narrow-angle glaucoma (NAG) treated with pilocarpine ± topical ß-blockers. Patients were treated in randomized, placebo-controlled, double-blind parallel-group fashion (15 : 9 attribution to P4 vs. placebo (PL)). TREATMENTS: Single-blind PL dose in the morning of day 1 for baseline; double-blind 15 mg P4 or matched placebo t.i.d. from the afternoon of day 1 until the morning of day 7. RESULTS: In the morning of day 7, trough mean serum P4 concentrations were 169.4 ng/mL (CV (coefficient of variation): 0.55) and 140.7 ng/mL (CV: 0.56) in OAG and NAG; at 3:15 hours after dosing: 237.4 ng/mL (CV: 0.47) and 212.4 ng/mL P4 (CV: 0.38), respectively. P4-treatment led to a prompt (OAG) or more gradient (NAG) increase in pupil diameter (PUD), with a maximum difference from PL of 0.97 mm (95% confidence interval (CI): 0.67 - 1.27) and 0.87 mm (95% CI: 0.36 - 1.39) in OAG and NAG, respectively. However, there was no average increase in intraocular pressure (IOP) or increase in noteworthy safety-relevant individual IOP values (or changes thereof). There was no effect on visual acuity or accommodation. CONCLUSIONS: 1-week treatment with P4 appeared to be safe 1) in OAG patients treated with topical ß-blockers and 2) in NAG patients treated with topical pilocarpine ± ß-blockers, irrespective of whether the eyes had previously been treated with glaucoma surgery or laser therapy.
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Modeling the heterogeneous intestinal absorption of propiverine extended-release.

Propiverine is a widely used antimuscarinic drug with bioavailability that is limited by intestinal first-pass extraction. To study the apparent heterogeneity in intestinal first-pass extraction, we performed a population analysis of oral concentration-time data measured after administration of an extended-release formulation of propiverine in ten healthy subjects. Using an inverse Gaussian function as input model, the assumption that the systemically available fraction increases as a sigmoidal function of time considerably improved the fit. The step-like increase in this fraction at time t=3.7h predicted by the model suggests that propiverine is predominantly absorbed in colon. A nearly perfect correlation was found between the estimates of bioavailability and mean dissolution time.

Improvement of trospium-specific absorption models for fasted and fed states in humans.

The purpose of this study was to mechanistically interpret the oral absorption pattern of trospium in fasted and fed states by means of gastrointestinal simulation technology. A drug absorption model was built on the basis of experimental data. According to the generated model, low permeability across the intestinal epithelium, delayed gastric emptying time and a prolonged residence time in the small intestine are the key factors governing trospium absorption in the fasted state. Furthermore, in silico modelling provided a plausible explanation of the pronounced reduction in the oral bioavailability of trospium when administered with food. The simulation results support the decreased dissolution in viscous medium, and the reduced drug permeability in the fed state as the predominant mechanisms for the food effect on trospium absorption.

Mechanistic basis for unexpected bioavailability enhancement of polyelectrolyte complexes incorporating BCS class III drugs and carrageenans.

The objective of this study was to investigate the potential of λ-carrageenan to work as an absorption modifying excipient in combination with formulations of BCS class 3 substances. Trospium chloride was used as a model BCS class 3 substance. Polyelectrolyte complexes of trospium and λ-carrageenan were produced by layer-by-layer complexation. A λ-carrageenan-containing formulation was administered either in capsules size 9 to rats by gavage or directly into ligated intestinal loops of rats. Exceptionally strong variations were observed in the plasma concentrations of the rats that received λ-carrageenan compared to the control group, but enhanced plasma concentrations were observed only in some of the rats. In vitro permeability studies were performed across Caco2-monolayers and across excised segments of rat jejunum in a modified Ussing chamber to learn more about the mechanism of absorption enhancement. The complex did not show any effect in Caco2-cells, but led to a major enhancement of permeability across excised segments in modified Ussing chambers. Carrageenan did not lead to alterations of tight junctions. The bioavailability enhancing effect thus was most likely due to an interaction of the polyelectrolyte-drug complex with the mucus, which provided an intimate contact between the drug and the absorbing surface. A similar effect was also achievable with other types of carrageenan and was also transferable to other compounds. In conclusion, λ-carrageenan-drug complexes show interesting excipient-drug-epithelium interactions - however, for full utilization of the permeation enhancing potential, an intimate and reproducible contact between absorbing epithelia and the complex is needed.

Influence of a fat-rich meal on bioavailability of extended-release and immediate-release propiverine.

The muscarinic receptor antagonist propiverine is unique insofar as extended-release (ER) tablets are of higher bioavailability than immediate-release (IR) tablets; this is caused by lower "first-pass" elimination of propiverine via CYP3A4 and efflux transporters in the distal small intestine and colon. Food may influence gastrointestinal transiting and, in turn, may affect regional absorption of propiverine IR and ER. Therefore, food effects on disposition of 30 mg IR and 45 mg ER were measured in a randomized, open, 4-period interaction study in 24 healthy participants. In fasting participants, ER had higher bioavailability than IR (F(rel) = 169%, P = .03). Fat-rich meal did not change the disposition of ER markedly (AUC(0-∞) ratio, 1.00 [90% confidence interval (CI), 0.90-1.11], C(max) ratio, 0.97 [0.87-1.09]). However, C(max) and renal A(e) of the major N-oxidized metabolite (M-5) significantly increased, whereas t(1/2) decreased. By eating a fat-rich meal before administration, the differences in absorption of IR and ER were nearly abolished (AUC(0-∞) ratio for propiverine, 1.12 [90% CI, 0.95-1.33]; AUC(0-∞) ratio for M-5, 0.89 [0.82-0.95]). In conclusion, propiverine ER has higher bioavailability than IR and no positive food effect because it reaches, independently of food, intestinal absorption areas with lower metabolism and efflux transport, which results in constant absorption rates.

Determination of propiverine hydrochloride in human plasma by high performance liquid chromatography-tandem mass spectrometry: application to the pharmacokinetic study of a sustained release formulation.

A rapid, sensitive and reliable high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated for the determination of propiverine hydrochloride (CAS 54556-98-8) in human plasma using cetirizine di-hydrochloride as internal standard (IS, CAS 8388-51-0). Following liquid-liquid extraction with ethyl acetate, the separation was performed on a reverse phase C18 column with a mobile phase consisted of methanol-ammonium acetate (pH 4.0; 10 mM) (70:30, v/v). The detection was performed by a triple-quadrupole mass spectrometer in the positive ion and multiple reaction monitoring (MRM) mode, m/z 368.3 --> 116.1 for propiverine and m/z 389.2 --> 201.0 for the IS. The calibration curve fitted well over the concentration range of 0.2-200 ng/mL (all the concentration data in this study are related to salt (propiverine hydrochloride)). The limit of detection (LOD) and lower limit of quantification (LLOQ) in human plasma were 0.05 and 0.2 ng/mL, respectively. The method was proved to be rapid, sensitive, specific, accurate and reproducible and has been successfully applied to a pharmacokinetic study of propiverine hydrochloride sustained release capsules (the 30 mg dose in this study is related to 30 mg of salt (propiverine hydrochloride)). The major pharmacokinetic parameters in healthy Chinese volunteers are given for the first time and the sustained release characteristics of the sustained release formulation are evaluated. [corrected].

The N-oxide metabolite contributes to bladder selectivity resulting from oral propiverine: muscarinic receptor binding and pharmacokinetics.

We characterized contribution of N-oxide metabolites [1-methyl-4-piperidyl diphenylpropoxyacetate N-oxide (M-1) and 1-methyl-4-piperidyl benzilate N-oxide (M-2)] to the binding of muscarinic receptors in relation to the pharmacokinetics of propiverine in rats. The in vitro muscarinic receptor binding activity of M-2 was equipotent to that of propiverine, whereas M-1 was much less active. After the oral administration of propiverine (24.8-248 micromol/kg), there was relatively selective and longer-lasting binding of muscarinic receptors in the rat bladder compared with the submaxillary gland as shown by a significant increase in the apparent dissociation constant (K(d)) for specific binding of [N-methyl-(3)H]scopolamine ([(3)H]NMS). In addition, the intravesical instillation of M-2 produced a significant increase in K(d) for specific [(3)H]NMS binding in the rat bladder. Extremely high concentrations of M-1 and M-2 were detected in plasma after the oral administration of propiverine. The concentration of unbound M-2 was much higher than that of M-1 and propiverine in the rat plasma. The sum of maximal plasma unbound propiverine equivalents (C(max)) after the oral administration of propiverine at doses of 24.8, 74.3, and 248 micromol/kg was 66.0, 303, and 509 nM, respectively. The sum of corresponding area under the time-concentration curve from 0 to 12 h was 194, 2123, and 4645 nM . h, respectively. In fact, the unbound concentration of M-2 comprised more than 90% of sum of unbound propiverine equivalents in the plasma. After oral treatment with propiverine, the bladder showed the highest concentration of M-2, indicating specific distribution of this metabolite into the target organ. Thus, M-2 may contribute greatly to the relatively selective and long-lasting occupation of bladder muscarinic receptors after oral administration of propiverine.

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.

Sensitive column-switching high-performance liquid chromatography method for determination of propiverine in human plasma.

A sensitive column-switching high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was developed for the determination of propiverine in human plasma. Propiverine and internal standard, oxybutynin, were extracted from human plasma that had been made basic with 5N sodium hydroxide into methyl tert-butyl ether. The extracted plasma sample was injected onto the HPLC system consisting of a pretreatment column, a concentrating column, and an analytical column, which were connected with a six-port switching valve. The assay was linear in concentration ranges of 2-200 ng/ml for propiverine in human plasma. This method showed excellent sensitivity (a limit of detection of 0.5 ng/ml), good precision and accuracy. This method is suitable for bioequivalence studies following single dose in healthy volunteers.

Quantification of propiverine by liquid chromatography/electrospray tandem mass spectrometry: application to a bioequivalence study of two formulations in healthy subjects.

Here we report on the development and validation of a sensitive and rapid reversed-phase liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitative determination of propiverine in human plasma. After adding an internal standard (oxybutynin chloride) to human plasma, samples were extracted using n-hexane/ethylacetate (8:2, v/v). Compounds extracted were analyzed by reversed-phase high-performance liquid chromatography (HPLC) with multiple reaction monitoring (MRM) mode for analyte detection. This method for determination of propiverine proved accurate and reproducible, with a limit of quantitation of 0.5 ng/ml in human plasma. The standard calibration curve for propiverine was linear (r2=0.9988) over the concentration range 0.5-1000.0 ng/ml in human plasma. The intra- and inter-day precision over this concentration range was lower than 8.66% (relative standard deviation, %R.S.D.), and accuracy was between 99.46 and 109.41%, respectively. This method was successfully applied to a bioequivalence study of two propiverine hydrochloride tablet formulations (20 mg) in 24 healthy subjects after a single administration.

Validation of a simple liquid chromatography-tandem mass spectrometric method for the determination of propiverine hydrochloride and its N-oxide metabolite in human plasma.

A simple high-performance liquid chromatography (HPLC)-tandem mass spectrometric method has been developed for determination of propiverine hydrochloride and its metabolite, propiverine N-oxide (M-1) in human plasma using stable isotopes, propiverine hydrochloride-d10 and M-1-d10, as internal standards. The analytes were extracted with dichloromethane from 0.2 ml of plasma in neutral condition (pH 7.0) and separated by HPLC on a C18 reversed-phase column using methanol-1% acetic acid (50:50) as a mobile phase, and detected using positive electrospray ionization in selected reaction monitoring (SRM) mode. The method was validated over a concentration range of 2-500 ng/ml for propiverine hydrochloride and 4-1000 ng/ml for M-1 using 0.2 ml of human plasma per assay. The method developed was successfully applied to analysis of propiverine hydrochloride and M-1 in clinical studies.

Increasing sample throughput in pharmacological studies by using dual-column liquid chromatography with tandem mass spectrometry.

A robust novel technology of parallel chromatography combined with tandem mass spectrometry was successfully applied to a biological matrix extract for analyte detection. The presented study shows how only by using an additional isocratic pump, a second column and a 10-port valve the throughput is twice of that of a conventional single column system with the same sensitivity. Analytes and matrix were separated and eluting peaks of the first column were detected while the second column was equilibrated. The system was tested and used for the determination of several drugs, metabolites and endogenous compounds (i.e., propiverine, talinolol, scopolamine and leukotrienes).

Evaluation of PET ligands (+)N-[(11)C]ethyl-3-piperidyl benzilate and (+)N-[(11)C]propyl-3-piperidyl benzilate for muscarinic cholinergic receptors: a PET study with microdialysis in comparison with (+)N-[(11)C]methyl-3-piperidyl benzilate in the conscious monkey brain.

We developed PET ligands (+)N-[(11)C]ethyl-3-piperidyl benzilate ([(11)C](+)3-EPB) and (+)N-[(11)C]propyl-3-piperidyl benzilate ([(11)C](+)3-PPB) for cerebral muscarinic cholinergic receptors. The distribution and kinetics of the novel ligands were evaluated for comparison with the previously reported ligand (+)N-[(11)C]methyl-3-piperidyl benzilate ([(11)C](+)3-MPB) in the monkey brain (Macaca mulatta) in the conscious state using high-resolution positron emission tomography (PET). At 60-91 min postinjection, regional distribution patterns of these three ligands were almost identical, and were consistent with the muscarinic receptor density in the brain as previously reported in vitro. However, the time-activity curves of [(11)C](+)3-EPB and [(11)C](+)3-PPB showed earlier peak times of radioactivity and a faster clearance rate than [(11)C](+)3-MPB in cortical regions rich in the receptors. Kinetic analysis using the three-compartment model with time-activity curves of radioactivity in metabolite-corrected arterial plasma as input functions revealed that labeling with longer [(11)C]alkyl chain length induced lower binding potential (BP = k(3)/k(4)), consistent with the rank order of affinity of these ligands obtained by an in vitro assay using rat brain slices and [(3)H]QNB. The cholinesterase inhibitor Aricept administered at doses of 50 and 250 microg/kg increased acetylcholine level in extracellular fluid of the frontal cortex and the binding of [(11)C](+)3-PPB with the lowest affinity to the receptors was displaced by the endogenous acetylcholine induced by cholinesterase inhibition, while [(11)C](+)3-MPB with the highest affinity was not significantly affected. Taken together, these observations indicate that the increase in [(11)C]alkyl chain length could alter the kinetic properties of conventional receptor ligands for PET by reducing the affinity to receptors, which might make it possible to assess the interaction between endogenous neurotransmitters and ligand-receptor binding in vivo as measured by PET.

A validated high-performance liquid chromatographic assay for the simultaneous determination of denaverine and its N-monodemethyl metabolite in human plasma.

An isocratic reversed-phase high-performance liquid chromatographic method for the simultaneous determination of denaverine and its N-monodemethyl metabolite (MD 6) in human plasma is described. The assay involves the extraction with an n-heptane-2-propanol mixture (9:1, v/v) followed by back extraction into 12.5% (w/w) phosphoric acid. The analytes of interest and the internal standard were separated on a Superspher RP8 column using a mobile phase of acetonitrile-0.12 M NH4H2PO4-tetrahydrofuran (24:17.2:1, v/v), adjusted to pH 3 with 85% (w/w) phosphoric acid. Ultraviolet detection was used at an operational wavelength of 220 nm. The retention times of MD 6, denaverine and the internal standard were 5.1, 6.3 and 10.2 min, respectively. The assay was validated according to international requirements and was found to be specific, accurate and precise with a linear range of 2.5-150 ng/ml for denaverine and MD 6. Extraction recoveries for denaverine and MD 6 ranged from 44 to 49% and from 42 to 47%, respectively. The stability of denaverine and MD 6 in plasma was demonstrated after 24 h storage at room temperature, after three freeze-thaw cycles and after 7 months frozen storage below -20 degrees C. The stability of processed samples in the autosampler at room temperature was confirmed after 24 h storage. The analytical method has been applied to analyses of plasma samples from a pharmacokinetic study in man.

High-performance liquid chromatographic determination of propiverine and its N-oxide in human serum.

A high-performance liquid chromatographic method has been developed for the determination of propiverine hydrochloride (P4) and its main metabolite, propiverine N-oxide (P4NO) in human serum. P4 has been shown to be efficacious in those patients who have either idiopathic bladder instability, or neurogenic bladder (detrusor hyperflexia) resulting from spinal cord injuries. In the present method, the analytes were extracted from serum (1 ml, pH 8) into methyl tert.-butyl ether. The separation was performed on a reversed-phase C8 (RP-select B) column using phosphate buffer-acetonitrile (30:70, v/v). UV absorption was used for measuring the analytes, with a limit of quantitation of about 10 ng/ml, which is appropriate for pharmacokinetic studies.

Quantitative capillary column gas chromatographic method for the determination of glycopyrronium in human plasma.

A new sensitive and selective capillary column gas chromatographic method for the anti-cholinergic agent glycopyrronium bromide in human plasma is described. The procedure involves preliminary ion-pair extraction of the drug into dichloromethane, followed by concentration and analysis of the ion-pair complex by capillary column gas chromatography using a nitrogen-sensitive detector. The method depends on the thermal dequaternisation of the quaternary ammonium compound and can be used to detect 5 ng/ml in a 3-ml plasma sample. The assay procedure has been applied to the determination of the plasma concentration of glycopyrronium after intravenous administration to an anaesthetised patient.