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

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.

Pharmacokinetics and bioavailability of denaverine hydrochloride in healthy subjects following intravenous, oral and rectal single doses

The neurotropic-musculotropic spasmolytic agent denaverine hydrochloride is used mainly in the treatment of smooth muscle spasms of the gastrointestinal and urogenital tract. Despite its commercial availability as a solution for intravenous or intramuscular administration (ampoule) and as a suppository formulation, no pharmacokinetic data in man was available to date. Therefore, the objectives of this clinical trial were to determine the basic pharmacokinetic parameters of denaverine after intravenous administration, to assess the feasibility of using the oral route of administration and to characterise the bioavailability of the suppository formulation. To achieve this, healthy subjects received 50 mg denaverine hydrochloride intravenously, orally and rectally in aqueous solutions and rectally as suppository in an open, randomised crossover design. Total body clearance, volume of distribution at steady-state and half-life of denaverine are 5.7 ml/min per kg, 7.1 l/kg and 33.8 h, respectively. The absolute bioavailability after oral administration of an aqueous solution is 37%. First-pass metabolism leading to the formation of N-monodemethyl denaverine was found to be one reason for the incomplete bioavailability after oral administration. Rectal administration of an aqueous solution of denaverine hydrochloride resulted in a decreased rate (median of C(max) ratios: 26%, difference in median t(max) values: 1.9 h) and extent (31%) of bioavailability compared to oral administration. Using the suppository formulation led to a further reduction in rate (median of C(max) ratios: 30%, difference in median t(max) values: 3 h) and extent (42%) of bioavailability compared to the rectal solution.