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

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.

Muscarinic Receptor Binding and Plasma Drug Concentration after the Oral Administration of Propiverine in Mice

OBJECTIVES

The current study was undertaken to characterize the binding of propiverine to muscarinic receptors in mouse tissues by measuring plasma concentrations of the drug and its metabolite.

METHODS

At 0.5-24 h after the oral administration of propiverine at pharmacologically relevant doses, muscarinic receptors in tissue homogenates were measured by a radioligand binding assay using [N-methyl- (3) H]scopolamine (NMS), along with the drug's concentration in plasma by the liquid chromatography-tandem mass spectrometric method.

RESULTS

In the in vitro experiments, propiverine and its metabolite 1-methy-4-piperidyl benzilate N-oxide competed with [(3) H]NMS for binding sites in the bladder, submaxillary gland and heart of mice in a concentration-dependent manner. After the oral administration of propiverine, dose- and time-dependent increases in the dissociation constant for specific [(3) H]NMS binding were observed in the bladder and other tissues of mice, indicating that orally administered propiverine and/or its metabolite undergo significant binding to muscarinic receptors in mouse tissues. A longer-lasting binding of muscarinic receptor was seen in the bladder than in the submaxillary gland at relatively low doses of propiverine. Furthermore, the decrease in maximal number of binding sites values for [(3) H]NMS binding was more remarkable in the bladder than submaxillary gland of propiverine treated mice. There was a dose-dependent rise in the plasma concentrations of propiverine and 1-methy-4-piperidyl benzilate N-oxide in mice after the oral administration of propiverine.

CONCLUSION

The oral administration of propiverine exerts a more prominent and longer-lasting effect in the bladder than in the submaxillary gland of mice. The N-oxide metabolite may contribute significantly to the blockade of muscarinic receptors caused by oral propiverine.

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.