Studies on the effect and mode of action of flavoxate in human urinary bladder and sphincter

Spectrofluorimetric determination of 3-methylflavone-8-carboxylic acid, the main active metabolite of flavoxate hydrochloride in human urine

A simple, sensitive and selective spectrofluorimetric method has been developed for the determination of 3-methylflavone-8-carboxylic acid as the main active metabolite of flavoxate hydrochloride in human urine. The proposed method was based on the measurement of the native fluorescence of the metabolite in methanol at an emission wavelength 390 nm, upon excitation at 338 nm. Moreover, the urinary excretion pattern has been calculated using the proposed method. Taking the advantage that 3-methylflavone-8-carboxylic acid is also the alkaline degradate, the proposed method was applied to in vitro determination of flavoxate hydrochloride in tablets dosage form via the measurement of its corresponding degradate. The method was validated in accordance with the ICH requirements and statistically compared to the official method with no significant difference in performance.

Flavoxate in urogynecology: an old drug revisited

INTRODUCTION AND HYPOTHESIS

Since its emergence in 1967, flavoxate has been used to treat several urogenital tract disorders irrespective of the etiology of the underlying disease, but the main indications have been overactive bladder and urge symptomatology. With the advances in anticholinergic drugs, its popularity has decreased in recent decades.

METHODS

In this review we summarize the current status of flavoxate in urogynecological practice focusing on its historical background, mechanism of action, efficacy, clinical experiences, outcomes, side effects and tolerability. We reviewed and analyze all the data and draw the major conclusions. We searched MEDLINE and the Cochrane Library using the keyword "flavoxate", and summarized review articles, original studies and case reports published from 1970 to 2013.

RESULTS AND CONCLUSION

We conclude that the minimal side effects and high tolerability of flavoxate make it worthy of consideration for the treatment of several clinical urogynecological conditions. It deserves more clinical studies to assess its efficacy as no randomized controlled trials have been performed with flavoxate during the last decade. More studies and novel drug formulations may reveal or improve its efficacy in daily practice.

Liquid Chromatographic Determination of Flavoxate HCl in Pharmaceutical Formulation

The objective of the study was to develop a high performance liquid chromatography (HPLC) method using ultra violet (UV) detection for the determination of flavoxate HCl in bulk and solid dosage forms by using ibuprofen as the internal standard. Eclipse C18 column (150 mm × 4.6 mm, 5 μm) was used as the stationary phase with a mixture of acetonitrile : 0.1% formic acid in water (75: 25 v/v) as the mobile phase. The response of the drug was linear in the concentration range of 1 – 250 μg/ml. Limit of detection and Limit of quantification were found to be 0.23 μg/ml and 0.69 μg/ml, respectively. The percentage of recovery ranged between 97.4 and 101.3%. The factors affecting column separation of the analyte were studied. The results demonstrated that this method is reliable, reproducible, and suitable for routine quantitative use.

Voltammetric quantitation at the mercury electrode of the anticholinergic drug flavoxate hydrochloride in bulk and in a pharmaceutical formulation

Flavoxate hydrochloride, 2-piperidinoethyl 3-methyl-4-oxo-2-phenyl-4-H-chromene-8-carboxylate, is a smooth muscle antispasmodic. Its electrochemical behavior was studied at the mercury electrode in buffered solutions containing 30% (v/v) methanol using dc-polarography, differential-pulse polarography, cyclic voltammetry, and linear sweep-and square-wave adsorptive stripping voltammetry. Sensitive and precise procedures were developed for determination of bulk flavoxate hydrochloride and in the pharmaceutical formulation Genurin® S.F, without sample pretreatment or extraction. Limits of quantitation (LOQ) of 1 × 10−5, 5 × 10−6, 1 × 10−8 and 1 × 10−9 M flavoxate hydrochloride were achieved by dc-polarography, differential-pulse polarography, linear sweep and square-wave adsorptive stripping voltammetric, respectively.

High performance liquid chromatographic determination of 3-methylflavone-8-carboxylic acid, the main active metabolite of flavoxate hydrochloride in human urine

High performance liquid chromatographic (HPLC) method was presented for the determination of 3-methylflavone-8-carboxylic acid as the main active metabolite of flavoxate hydrochloride (FX) in human urine. The proposed method was based on using CN column with mobile phase consisting of acetonitrile-12 mM ammonium acetate (40:60, v/v) and adjusted to apparent pH 4.0 with flow rate of 1.5 ml min(-1). Quantitation was achieved with UV detection at 220 nm. The proposed method was utilized to the determination of dissolution rate for tablets containing flavoxate hydrochloride. The urinary excretion pattern has been calculated using the proposed method.

Conformational evaluation and detailed 1H and 13C NMR assignments of flavoxate, a urinary tract antispasmodic agent

1H and 13C NMR chemical shift assignments for the urinary tract antispasmodic flavoxate (1) and flavoxate hydrochloride (2) were obtained from one- and two-dimensional measurements. A Monte Carlo random search using molecular mechanics, followed by geometry optimization of each minimum energy structure employing DFT calculations at the B3LYP/6-31G* level, and a Boltzmann analysis of the total energies, provided accurate molecular models which describe the conformational behavior of flavoxate (1). The electron density surfaces for the global minimum and the second minimum conformers 1a and 1b of this L-type Ca2+ channel inhibitor were calculated. The presence of both conformers in solution was demonstrated in full agreement with 2D NOESY data and NOE difference spectroscopy.

The biochemistry and medical significance of the flavonoids

Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.

Development of a high-performance liquid chromatographic method for bioequivalence study of flavoxate tablets

An improved HPLC method was developed for the concentration determination of the metabolite of flavoxate, 3-methyl-flavone-8-carboxylic acid (MFCA), in plasma in an attempt to compare two flavoxate tablet formulations. This HPLC method was validated by examining the precision and the accuracy for inter-day and intra-day runs in a linear concentration range of 0.1-24 microg/ml. The coefficients of variation (C.V.) of inter-day and intra-day assays were 0.24-7.18% and 0.06-5.70%, respectively. The standard errors of mean (S.E.M.) were -0.004-8.68% and -2.52-4.86% for inter-day and intra-day assays, respectively. Bioequivalence of the two formulations was determined on 12 normal healthy male volunteers in a single-dose, two-period, two-sequence, two-treatment crossover study. MFCA plasma concentrations were analyzed with this validated HPLC method. The normal pivotal parameters, AUC(0-last), AUC(0-inf) and Cmax, were calculated and compared using the SAS General Linear Model computer program. The two one-sided t distribution test was also performed, as well as the 90% confidence-interval method, for the mean difference of the three pivotal parameters. The results suggest that these two flavoxate tablet formulations are non-bioequivalent when orally administered in a 400-mg dose of two tablets. This result was consistent with the in vitro dissolution of these two formulations.

Antispasmodic effects of flavoxate, MFCA, and REC 15/2053 on smooth muscle of human prostate and urinary bladder

The antispasmodic effects of the flavone compounds flavoxate hydrochloride, 3-methylflavone carboxylic acid (MFCA), and REC 15/2053 (and in the case of the detrusor, oxybutynin), on the human detrusor, prostatic adenoma, prostatic capsule, and bladder neck, were studied by the in vitro isometric method. All the compounds inhibited, in different orders of potency, potassium-induced contractions of the tissues. Flavoxate showed a slightly greater activity than the other two compounds in the prostatic and bladder neck tissues. However, REC 15/2053 displayed greater activity in the detrusor than in the other tissues. The relaxant effect on the prostatic tissues suggests a potential use for these compounds in benign prostatic obstruction.

Randomized, double-blind, multicenter trial on treatment of frequency, urgency and incontinence related to detrusor hyperactivity: oxybutynin versus propantheline versus placebo

Clinical efficacy and adverse effects of oxybutynin and propantheline in the treatment of symptoms related to detrusor hyperactivity were studied in a randomized, controlled, double-blind multicenter trial. Of 169 patients entered into the study 154 were evaluable for statistical analysis. Mean grade of improvement (visual analogue scale) was significantly higher with oxybutynin (58.2%) versus propantheline (44.7%) and placebo (43.4%). Mean bladder volume at first involuntary cystometric contraction was significantly increased with oxybutynin (+57.0 ml.) versus placebo (-9.7 ml.). Mean maximum cystometric bladder capacity was also significantly increased with oxybutynin (+80.1 ml.) versus placebo (+22.5 ml.). Rate of inquired possible adverse effects was significantly higher for oxybutynin (63%) versus propantheline (44%) and placebo (33%). However, only 5 patients dropped out of the study because of adverse effects (oxybutynin 2 and propantheline 3). No serious or lasting adverse effects were encountered with dryness of the mouth being the major complaint. Oxybutynin has statistically significant effects on subjective symptoms and objective urodynamic parameters in patients with detrusor hyperactivity compared to propantheline.

A calcium blocking and anticholinergic agent (terodiline) in the treatment of detrusor hyperreflexia: a placebo-controlled, cross-over trial

In 25 neurological patients with detrusor hyperreflexia terodiline reduced the number of total micturitions during daytime. Bladder capacity was increased and amplitude of the bladder contractions was reduced. An increase in residual urine was also observed. Mild anticholinergic side-effects were measured on pupillary motility and on heart rate variation. It is concluded that terodiline is a useful alternative in treatment of patients with detrusor hyperreflexia.

Emepronium bromide and flavoxate hydrochloride in the treatment of urinary incontinence associated with detrusor instability in elderly women

A 4-week randomised, double-blind, cross-over study is described which compared the effects of a combination of emepronium bromide and flavoxate hydrochloride with placebo on incontinence and cystometrogram findings in 20 female patients aged 59 to 88 years. All patients initially had detrusor instability demonstrated on cystometrography: 14 patients completed the study; on placebo 10 still had unstable bladders and on active drugs seven were unstable. The number of wettings over a 48-h period before the study commenced and at the end each course of tablets showed no significant differences; also the patients' opinions about the effect on their incontinence indicated that the majority had the same opinion of each course. Active drugs significantly increased residual urine but did not significantly alter the values obtained for maximum cystometric capacity or effective cystometric capacity (the latter volume being maximum cystometric capacity minus the residual urine). No correlation was found, on either course of treatment, between the change to detrusor stability and the amount of improvement in incontinence. Some side effects are described. Despite evidence of a pharmacological effect on the bladder and patients' opinions tending to favour the active combination, nonetheless the main results of this small study do not suggest that the combination of emepronium bromide and flavoxate hydrochloride is an effective treatment of urinary incontinence associated with detrusor instability in elderly women.

Flavonoids, a class of natural products of high pharmacological potency

A review has been presented of the biochemistry and pharmacology of a class of natural products, the flavonoids. These substances which are widely distributed in the plant kingdom and present in considerable quantities in common food products, spices and beverages have in a concentrated form (Propolis) been used since ancient times by physicians and laymen to treat a great variety of human diseases but they have yet to pass the tests of modern, controlled, clinical experimentation. An attempt has been made to present the fundamental evidence from the basic biological sciences which is required to stimulate the interest of the clinicians in this new field. The few existing reports on the careful pharmacodynamic, pharmacokinetic and clinical studies which have been made have been summarized to provide a basis for a full-scale investigation of the therapeutic potential of flavonoids.

An objective comparison of the effects of parenterally administered drugs in patients suffering from detrusor instability

Cystometric changes produced by 3 parenterally administered drugs, flavoxate hydrochloride, emepronium bromide and imipramine hydrochloride, have been evaluated in 15 female patients with detrusor instability. Each patient was given 2 of the 3 drugs and cystometric recordings were done 10 and 30 minutes after the administration of each drug. Emepronium bromide was found to be the only drug to cause a significant improvement in bladder capacity and reduction in detrusor pressure.

Effect of dantrolene sodium on the spastic external urethral sphincter recorded by sphincterometry

An improved method of sphincterometry is described, which is easy to perform in men and also may be used in women. It gives reproducible results in the individual patient. The maximum pressure was found by radiographic and reflexological examinations of the external urethral sphincter. When 0.5 mg./kg. body weight dantrolene sodium was injected intravenously the resistance of the external urethral sphincter was found to be reduced significantly, presumably reflecting a reduction of reflex activity.