Use of Physiologically Based Pharmacokinetic Modeling for Predicting Drug-Food Interactions: Recommendations for Improving Predictive Performance of Low Confidence Food Effect Models.

Food can alter drug absorption and impact safety and efficacy. Besides conducting clinical studies, in vitro approaches such as biorelevant solubility and dissolution testing and in vivo dog studies are typical approaches to estimate a drug's food effect. The use of physiologically based pharmacokinetic models has gained importance and is nowadays a standard tool for food effect predictions at preclinical and clinical stages in the pharmaceutical industry. This manuscript is part of a broader publication from the IQ Consortium's food effect physiologically based pharmacokinetic model (PBPK) modeling working group and complements previous publications by focusing on cases where the food effect was predicted with low confidence. Pazopanib-HCl, trospium-Cl, and ziprasidone-HCl served as model compounds to provide insights into why several food effect predictions failed in the first instance. Furthermore, the manuscript depicts approaches whereby PBPK-based food effect predictions may be improved. These improvements should focus on the PBPK model functionality, especially better reflecting fasted- and fed-state gastric solubility, gastric re-acidification, and complex mechanisms related to gastric emptying of drugs. For improvement of in vitro methodologies, the focus should be on the development of more predictive solubility, supersaturation, and precipitation assays. With regards to the general PBPK modeling methodology, modelers should account for the full solubility profile when modeling ionizable compounds, including common ion effects, and apply a straightforward strategy to account for drug precipitation.

Trospium Chloride Transport by Mouse Drug Carriers of the Slc22 and Slc47 Families.

BACKGROUND: The muscarinic receptor antagonist trospium chloride (TCl) is used for pharmacotherapy of the overactive bladder syndrome. TCl is a hydrophilic positively charged drug. Therefore, it has low permeability through biomembranes and requires drug transporters for distribution and excretion. In humans, the organic cation transporters OCT1 and OCT2 and the multidrug and toxin extrusion MATE1 and MATE2-K carriers showed TCl transport. However, their individual role for distribution and excretion of TCl is unclear. Knockout mouse models lacking mOct1/mOct2 or mMate1 might help to clarify their role for the overall pharmacokinetics of TCl. METHOD: In preparation of such experiments, TCl transport was analyzed in HEK293 cells stably transfected with the mouse carriers mOct1, mOct2, mMate1, and mMate2, respectively. RESULTS: Mouse mOct1, mOct2, and mMate1 showed significant TCl transport with Km values of 58.7, 78.5, and 29.3 µM, respectively. In contrast, mMate2 did not transport TCl but showed MPP+ transport with Km of 60.0 µM that was inhibited by the drugs topotecan, acyclovir, and levofloxacin. CONCLUSION: TCl transport behavior as well as expression pattern were quite similar for the mouse carriers mOct1, mOct2, and mMate1 compared to their human counterparts.

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.

Effects of the P-Glycoprotein Inhibitor Clarithromycin on the Pharmacokinetics of Intravenous and Oral Trospium Chloride: A 4-Way Crossover Drug-Drug Interaction Study in Healthy Subjects.

The quaternary ammonium compound trospium chloride is poorly absorbed from 2 "absorption windows" in the jejunum and cecum/ascending colon, respectively. To confirm whether intestinal P-glycoprotein (P-gp) is involved, a 4-period, crossover drug interaction study with trospium chloride after intravenous (2 mg) and oral administration (30 mg) without and after comedication of clarithromycin (500 mg), an inhibitor for P-gp, was initiated in 12 healthy subjects. Pharmacokinetics of trospium was evaluated using gas chromatography-mass spectrometry, noncompartmental evaluation, and pharmacokinetic modeling. Trospium chloride was poorly absorbed after oral administration (absolute bioavailability, ∼8%-10%). About 30% of the bioavailable dose fraction was absorbed from the "narrow window". Comedication with clarithromycin increased steady-state distribution volumes by ∼27% (P < .01). Bioavailability was not increased as hypothesized. The geometric mean ratios (90% confidence interval) for area under the plasma concentration-time curve, maximum concentration, and renal clearance accounted for 0.75 (0.56-1.01), 0.64 (0.45-0.89), and 1.00 (0.90-1.13), respectively. The amount of trospium absorbed from the "narrow window" was reduced in all subjects but from the "wider window" in only 9 of them. Bioavailability was strongly predicted by the maximum absorption rate of trospium in the distal "window" (rs2  = 0.910, P < .0001). In conclusion, the P-gp inhibitor clarithromycin significantly increases distribution volumes but not oral absorption of trospium. The amount absorbed from the "narrow window" was lowered in all subjects. However, the extent of all influences seems not to be of clinical relevance.

Designing robust immediate release tablet formulations avoiding food effects for BCS class 3 drugs.

Food induced viscosity in the gastrointestinal tract is reported to reduce the bioavailability of tablets containing BCS class 3 drugs, mainly by retarding their disintegration and dissolution of the active pharmaceutical ingredient. The role of formulation factors in minimizing this negative food effect is largely unknown. Combinations of disintegrants were studied together with soluble and insoluble fillers and trospium chloride as model drug substance. Different batches of tablets were compressed at 10 kN and 30 kN, by incorporating different combinations of croscarmellose sodium (CSS), cross-linked (CPD) and sodium starch glycolate (SSG) at low level i.e, 2% + 2% and high level i.e, 4% + 4% of compressional weight, while taking lactose as a soluble filler and dibasic calcium phosphate (DCP) and microcrystalline cellulose (MCC) as insoluble fillers. Under low viscous conditions, disintegration of DCP based tablets was faster compared to lactose based tablets, but under high viscous conditions, simulating the effect of an ingested FDA meal, the disintegration behavior was reverted. Increased compressional force prolonged the disintegration of lactose and DCP based formulations under fasted conditions. However, when evaluated under food viscosity conditions, DCP based tablets compressed at higher force showed rapid disintegration while no effect of increased compressional force in lactose based tablets was observed. MCC based tablets in particular showed largely prolonged disintegration times in viscous media irrespective of the disintegrant type and levels investigated. Disintegrant combinations possessing wicking ability with minimum or no gelling were found to reduce disintegration times. The disintegrant combination of CPD + CCS was effective in reducing disintegration and enhancing dissolution besides not being affected by changes in compressional force and their total proportion in the tablet. In conclusion, it is recommended to evaluate formulations under increased viscosity conditions during the development phase of tablets with an objective to minimize the negative effect of food viscosity on disintegration and dissolution.

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.

Expression of drug transporters and drug metabolizing enzymes in the bladder urothelium in man and affinity of the bladder spasmolytic trospium chloride to transporters likely involved in its pharmacokinetics.

The cationic, water-soluble quaternary trospium chloride (TC) is incompletely absorbed from the gut and undergoes wide distribution but does not pass the blood-brain barrier. It is secreted by the kidneys, liver, and intestine. To evaluate potential transport mechanisms for TC, we measured affinity of the drug to the human uptake and efflux transporters known to be of pharmacokinetic relevance. Affinity of TC to the uptake transporters OATP1A2, -1B1, -1B3, -2B1, OCT1, -2, -3, OCTN2, NTCP, and ASBT and the efflux carriers P-gp, MRP2 and MRP3 transfected in HEK293 and MDCK2 cells was measured. To identify relevant pharmacokinetic mechanisms in the bladder urothelium, mRNA expression of multidrug transporters, drug metabolizing enzymes, and nuclear receptors, and the uptake of TC into primary human bladder urothelium (HBU) cells were measured. TC was shown to be a substrate of OATP1A2 (Km = 6.9 ± 1.3 µmol/L; Vmax = 41.6 ± 1.8 pmol/mg·min), OCT1 (Km = 106 ± 16 µmol/L; Vmax = 269 ± 18 pmol/mg·min), and P-gp (Km = 34.9 ± 7.5 µmol/L; Vmax = 105 ± 9.1 pmol/mg·min, lipovesicle assay). The genetic OATP1A2 variants *2 and *3 were loss-of-function transporters for TC. The mRNA expression analysis identified the following transporter proteins in the human urothelium: ABCB1 (P-gp), ABCC1-5 (MRP1-5), ABCG2 (BCRP), SLCO2B1 (OATP2B1), SLCO4A1 (OATP4A1), SLC22A1 (OCT1), SLC22A3 (OCT3), SLC22A4 (OCTN1), SLC22A5 (OCTN2), and SLC47A1 (MATE1). Immuno-reactive P-gp and OATP1A2 were localized to the apical cell layers. Drug metabolizing enzymes CYP3A5, -2B6, -2B7 -2E1, SULT1A1-4, UGT1A1-10, and UGT2B15, and nuclear receptors NR1H3 and NR1H4 were also expressed on mRNA level. TC was taken up into HBU cells (Km = 18.5 ± 4.8 µmol/L; Vmax = 106 ± 11.3 pmol/mg·min) by mechanisms that could be synergistically inhibited by naringin (IC50 = 10.8 (8.4; 13.8) µmol/L) and verapamil (IC50 = 4.6 (2.8; 7.5) µmol/L), inhibitors of OATP1A2 and OCT1, respectively. Affinity of TC to OCT1 and P-glycoprotein may be the reason for incomplete oral absorption, wide distribution into liver and kidneys, and substantial intestinal and renal secretions. Absence of brain distribution may result from affinity to P-gp and a low affinity to OATP1A2. The human urothelium expresses many drug transporters and drug metabolizing enzymes that may interact with TC and other drugs eliminated into the urine.

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.

Superiority of pulmonary administration of mepenzolate bromide over other routes as treatment for chronic obstructive pulmonary disease.

We recently proposed that mepenzolate bromide (mepenzolate) would be therapeutically effective against chronic obstructive pulmonary disease (COPD) due to its both anti-inflammatory and bronchodilatory activities. In this study, we examined the benefits and adverse effects associated with different routes of mepenzolate administration in mice. Oral administration of mepenzolate caused not only bronchodilation but also decreased the severity of elastase-induced pulmonary emphysema; however, compared with the intratracheal route of administration, about 5000 times higher dose was required to achieve this effect. Intravenously or intrarectally administered mepenzolate also showed these pharmacological effects. The intratracheal route of mepenzolate administration, but not other routes, resulted in protective effects against elastase-induced pulmonary damage and bronchodilation at a much lower dose than that which affected defecation and heart rate. These results suggest that the pulmonary route of mepenzolate administration may be superior to other routes (oral, intravenous or intrarectal) to treat COPD patients.

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.

Ion pairing with bile salts modulates intestinal permeability and contributes to food-drug interaction of BCS class III compound trospium chloride.

In the current study the involvement of ion pair formation between bile salts and trospium chloride (TC), a positively charged Biopharmaceutical Classification System (BCS) class III substance, showing a decrease in bioavailability upon coadministration with food (negative food effect) was investigated. Isothermal titration calorimetry provided evidence of a reaction between TC and bile acids. An effect of ion pair formation on the apparent partition coefficient (APC) was examined using (3)H-trospium. The addition of bovine bile and bile extract porcine led to a significant increase of the APC. In vitro permeability studies of trospium were performed across Caco-2-monolayers and excised segments of rat jejunum in a modified Ussing chamber. The addition of bile acids led to an increase of trospium permeation across Caco-2-monolayers and rat excised segments by approximately a factor of 1.5. The addition of glycochenodeoxycholate (GCDC) was less effective than taurodeoxycholate (TDOC). In the presence of an olive oil emulsion, a complete extinction of the permeation increasing effects of bile salts was observed. Thus, although there are more bile acids in the intestine in the fed state compared to the fasted state, these are not able to form ion pairs with trospium in fed state, because they are involved in the emulsification of dietary fats. In conclusion, the formation of ion pairs between trospium and bile acids can partially explain its negative food effect. Our results are presumably transferable to other organic cations showing a negative food effect.

Propiverine: a review of its use in the treatment of adults and children with overactive bladder associated with idiopathic or neurogenic detrusor overactivity, and in men with lower urinary tract symptoms.

Propiverine is a well established antimuscarinic agent with a mixed mode of action in the treatment of symptoms associated with overactive bladder (OAB). As well as blocking muscarinic receptors in the detrusor muscle, the drug also inhibits cellular calcium influx, thereby diminishing muscle spasm. In patients with symptoms of OAB resulting from idiopathic detrusor overactivity (IDO) or neurogenic detrusor overactivity (NDO), propiverine demonstrated dose-dependent efficacy and tolerability, with adverse events consistent with those associated with all antimuscarinic agents. In adults with IDO, propiverine demonstrated similar efficacy to that of other antimuscarinic agents (including solifenacin, tolterodine, oxybutynin and imidafenacin) and, in adults with NDO, propiverine and oxybutynin demonstrated similar efficacy. Propiverine was generally well tolerated in these patient populations, with a lower incidence of dry mouth than that associated with oxybutynin. In men with lower urinary tract symptoms (LUTS), and in whom the presence of benign prostatic enlargement (BPE) was implicated, propiverine administered as add-on therapy to an α(1)-adrenoceptor antagonist demonstrated similar or superior efficacy to that achieved with an α(1)-adrenoceptor antagonist alone, and combination therapy was particularly effective in patients with urinary storage symptoms. Combination therapy was generally well tolerated, but was associated with a higher incidence of adverse events than an α(1)-adrenoceptor antagonist alone. In children and adolescents with IDO/OAB or NDO, propiverine was generally more effective and better tolerated than oxybutynin. In conclusion, propiverine provides a valuable option for the treatment of adults and children with OAB associated with IDO or NDO, and in men with storage LUTS.

Brain penetration of the OAB drug trospium chloride is not increased in aged mice.

PURPOSE: To analyse whether the permeability of the blood-brain barrier to the antimuscarinic drug trospium chloride is altered with ageing. This is a relevant question for elderly patients with overactive bladder syndrome who are treated with trospium chloride as the occurrence of adverse effects on the central nervous system (CNS) highly depends on the absolute drug concentration in the brain. METHODS: Trospium chloride at 1 mg/kg was intravenously administered to adult, middle-aged, and aged mice at 6, 12, and 24 months of age, respectively, and the absolute drug concentrations in the brain were analysed after 2 h. Furthermore, mRNA expression levels of relevant markers of blood-brain barrier integrity (occludin, claudin-5, and the drug efflux carrier P-glycoprotein) were analysed in brain samples from adult and aged mice. RESULTS: The absolute brain concentrations of the drug were identical in adult and middle-aged mice (13 ± 2 ng/g vs. 13 ± 2 ng/g) and were slightly, but significantly, lower in aged mice (8 ± 4 ng/g). The brain/plasma drug concentration ratios were not different between the age groups and demonstrated the generally low capability of trospium chloride in permeating the blood-brain barrier. Occludin, claudin-5, and P-glycoprotein showed identical mRNA expression levels in the brains of adult and aged mice. CONCLUSION: Based on our in vivo data in a mouse model, we conclude that trospium chloride permeation across the BBB is not increased in ageing per se, and therefore, the occurrence of adverse CNS drug effects is also not expected to increase with ageing.

Study of the population pharmacokinetic characteristics of once-daily trospium chloride 60 mg extended-release capsules in patients with overactive bladder and in healthy subjects.

BACKGROUND: Overactive bladder is a common disorder that affects approximately 34 million adults in the United States. Anticholinergic (antimuscarinic) agents are the most widely used pharmacological option for overactive bladder. OBJECTIVE: This study set out to identify and characterize the influence of a number of intrinsic characteristics on the pharmacokinetics of the anticholinergic agent trospium chloride (Sanctura(®)) 60 mg extended release (XR), and to evaluate the correlation between trospium chloride exposure and key efficacy and safety outcomes in subjects and patients. STUDY DESIGN: Pharmacokinetic data were obtained from three studies in which a total of 349 subjects received trospium chloride XR for up to 12 weeks. Plasma trospium chloride concentration data were pooled and a population pharmacokinetic model was derived using non-linear mixed-effects modelling. Demographic factors were assessed for influence on the model. The correlation between trospium chloride exposure and key efficacy variables was evaluated. Correlations between exposure and safety outcomes were also assessed. INTERVENTION: Trospium chloride XR 60 mg once daily for 10 days in healthy volunteers or trospium chloride 60 mg XR once daily for either 2 weeks or 12 weeks in patients with overactive bladder. RESULTS: The best population pharmacokinetic model was determined to be a two-compartment model with zero-order release into the depot compartment and first-order absorption. Body surface area (BSA) was the only covariate to significantly (P < 0.05) impact trospium chloride 60 mg XR pharmacokinetics. Significant relationships (P < 0.05) were observed between exposure [maximum plasma concentration (C(max)) and the area under the plasma concentration-time curve from time zero to 24 h (AUC(24))] and efficacy outcomes in the <65-year age group for change in average number of voids/day, change in number of incontinence episodes, and change in urgency severity, and in the ≥65-year age group statistical significance (P < 0.05) was achieved for C(max), but not for AUC(24), for these same three efficacy measures. Statistically significant relationships (P < 0.004) were also observed between exposure and both dry mouth and constipation, with increased benefit and increased incidence of adverse events (AEs) associated with higher concentrations; the correlation coefficients were low against the aggregate of AEs of interest (0.19 for AUC(24) and 0.18 for C(max)), indicating only mild strength of association. CONCLUSION: This population pharmacokinetic analysis demonstrated that the only demographic characteristic associated with trospium chloride pharmacokinetics was BSA. Thus, treatment of most patients with overactive bladder with once-daily trospium chloride 60 mg XR should not require consideration of key intrinsic demographic parameters. Furthermore, while efficacy and tolerability outcomes were found to be correlated with trospium chloride exposure, the strength of the association was modest in this study.

Taste masking of propiverine hydrochloride by conversion to its free base.

The aim of the present study was to mask the bitterness of propiverine hydrochloride (P-4) by converting it to propiverine free base. Fine granules comprising the free base, which was converted from P-4 by desalination, were prepared. By using Fourier transform infrared spectroscopy, thermogravimetry-differential thermal analysis, and powder X-ray diffraction spectra, we confirmed that P-4 had been converted into propiverine free base by desalination during the manufacturing process. Furthermore, the conversion into free base appeared to result in decreased solubility, and both the taste testing sensor and tasting volunteers determined that it masked the bitterness of P-4. On using the gustatory sensation test, the bitterness of the P-4 fine granules was confirmed to be weakened. The dissolution rate and bioavailability of fine granules of the free base were compared with tablets of P-4. The dissolution rate and bioavailability of the fine granules and tablets were almost the same. We successfully masked the taste of P-4 by converting it into free base using a manufacturing process that was suitable for commercial manufacturing.

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 influence of propiverine hydrochloride on cardiac repolarization in healthy women and cardiac male patients.

OBJECTIVE: Two comprehensively designed mono-centric ECG studies were performed to investigate the influence of propiverine hydrochloride and its main metabolite propiverine-N-oxide on cardiac function with regard to QTc prolongation, QTc dispersion and T-wave shape. METHODS: The first study was conducted on 24 healthy females, followed by a second study on 24 male patients with coronary heart disease (CHD) and a pathological Pardee-Q-wave in the ECG. Both studies were placebo-controlled and compared the effects of single (30 mg s.i.d.) and multiple dosing (15 mg t.i.d.) of propiverine hydrochloride in a crossover design over 6 and 13 days, respectively. In CHD patients, the ECG was recorded under standardized exercise stress conditions. RESULTS: An effect of propiverine on cardiac safety in healthy women and male patients with CHD could not be determined by the evaluation of QTc intervals derived from ECG under the following conditions: (1) single dosage; (2) steady-state and elevated dosage; (3) healthy female volunteers and male CHD patients; (4) resting and stress conditions in CHD patients. Moreover, other ECG parameters like QT dispersion, T-wave shape, and U-wave occurrence were not affected by propiverine compared to placebo after single or repeated dosing to reach steady-state conditions. CONCLUSION: These results reflect and confirm preclinical data as well as clinical observations on hundreds of volunteers and numberless patients suffering from overactive bladder syndrome and neurogenic detrusor overactivity who were treated with propiverine hydrochloride over nearly three decades in Europe and Japan.

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.