Mechanisms of the suppression of the bladder activity by flavoxate

Short-Term Flavoxate Treatment Alters Detrusor Contractility Characteristics: Renewed Interest in Clinical Use?

OBJECTIVES

Flavoxate has had a long history of use in the treatment of overactive bladder, despite the lack of documentation on its clinical efficacy and mechanism(s) of action. This study was conducted to understand how contractility characteristics of the detrusor are affected after a short period of flavoxate treatment.

METHODS

Eight-week-old mice were treated with flavoxate for 5 days and detrusor contractile responses were examined ex vivo under different pharmacological and electrical stimuli.

RESULTS

K(+) -Krebs'-induced contraction developed more slowly while 64 Hz electrical field stimulation-induced contraction developed faster in flavoxate-treated strips when compared to control. Amplitudes of maximal and steady-state contraction induced by 3 µmol/L carbachol were also larger after flavoxate treatment. Control strips showed an overall greater dependence on stimulus strength in eliciting the responses.

CONCLUSIONS

These findings provided new information of how short-term flavoxate treatment altered contractility characteristics at the bladder level, which may instill new interest in investigating the use of this drug in bladder disorders not responding well to conventional treatments.

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.

Effects of flavoxate hydrochloride on voltage-dependent Ba2+ currents in human detrusor myocytes at different experimental temperatures

The inhibitory effects of flavoxate hydrochloride (piperidinoethyl-3-methylflavone-8-carboxylate; hereafter referred as flavoxate) on voltage-dependent nifedipine-sensitive inward Ba2+ currents (I Ba) in human detrusor myocytes were investigated at different temperatures using conventional whole-cell patch-clamp techniques. When the bath-solution temperature was increased from 22 degrees C to 30 degrees C, I Ba peak amplitude was enhanced by approximately twice at several test potentials. Neither the I Ba threshold nor the membrane potentials for the I Ba maximum peak amplitude was affected by the temperature change. The concentration-response curves of flavoxate at both 30 degrees C (Ki = 5.1 microM) and 37 degrees C (Ki = 4.6 microM) were slightly shifted to the left in comparison with that at 22 degrees C (Ki = 10.3 microM). Similar results were also obtained in the presence of nifedipine (Ki = 14 nM at 22 degrees C vs. Ki = 2.5 nM at 30 degrees C and Ki = 2.1 nM at 37 degrees C). Altering the bath-solution temperature from 22 degrees C to 30 degrees C shifted the steady-state inactivation curve of I Ba at -90 mV to the left. At 30 degrees C, the steady-state inactivation curve of I Ba in the presence of flavoxate was also shifted to the left in comparison with that in the absence of flavoxate. Either 3-isobutyl-1-methylxanthine (IBMX) or theophylline, a phosphodiesterase inhibitor, caused little effects on I Ba, although cyclic nucleotides (dibutyryl cAMP and 8-Br-cGMP) inhibited I Ba. These results suggest that the inhibitory actions of flavoxate on I Ba in human detrusor myocytes were slightly changed at different experimental temperatures and that flavoxate directly blocked voltage-dependent L-type Ca2+ channels, not through the inhibition of phosphodiesterase activity pathway.

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.

Inhibitory effect of the nucleus reticularis pontis oralis on the pontine micturition center and pontine urine storage center in decerebrate cats

The influence of the nucleus reticularis pontis oralis (PoO) on the pontine micturition center (PMC) and pontine urine storage center (PUSC) was examined in decerebrate cats by electrical and chemical stimulations of the PMC, PUSC or PoO. Microinjection of carbachol into the rostral and dorsolateral part of the PoO rapidly inhibited reflex micturition and external urethral sphincter (EUS) activity. After confirming the inhibition of reflex micturition and EUS activity by microinjection of carbachol into the PoO, intravenous injection of atropine sulfate or its microinjection into the PoO recovered both reflex micturition and EUS activity. Microinjection of carbachol into the PMC evoked micturition and then inhibited reflex micturition, but intravenous injection of atropine or its microinjection into the PoO recovered reflex micturition. After confi rming the inhibition of reflex micturition and EUS activity by microinjection of carbachol into the PoO, electrical stimulation of the PUSC enhanced EUS activity, but electrical stimulation of the PMC failed to evoke micturition. However, electrical stimulation of the PMC evoked micturition after microinjection of atropine into the PoO. These results suggest that the PoO strongly inhibits the PMC and less strongly inhibits the PUSC. Therefore, the PoO seems to be the pontine micturition inhibitory area.

The effects of flavoxate hydrochloride on voltage-dependent L-type Ca2+ currents in human urinary bladder

The effects of flavoxate hydrochloride (Bladderon, piperidinoethyl-3-methylflavone-8-carboxylate; hereafter referred as flavoxate) on voltage-dependent nifedipine-sensitive inward Ba(2+) currents in human detrusor myocytes were investigated using a conventional whole-cell patch-clamp. Tension measurement was also performed to study the effects of flavoxate on K(+)-induced contraction in human urinary bladder. Flavoxate caused a concentration-dependent reduction of the K(+)-induced contraction of human urinary bladder. In human detrusor myocytes, flavoxate inhibited the peak amplitude of voltage-dependent nifedipine-sensitive inward Ba(2+) currents in a voltage- and concentration-dependent manner (K(i) = 10 microM), and shifted the steady-state inactivation curve of Ba(2+) currents to the left at a holding potential of -90 mV. Immunohistochemical studies indicated the presence of the alpha(1C) subunit protein, which is a constituent of human L-type Ca(2+) channels (Ca(V)1.2), in the bundles of human detrusor smooth muscle. These results suggest that flavoxate caused muscle relaxation through the inhibition of L-type Ca(2+) channels in human detrusor.

Activation of the rostral pontine reticular formation increases the spinal glycine level and inhibits bladder contraction in rats

PURPOSE

We examined the mechanism involved in the inhibition of bladder activity in rats by stimulating the rostral pontine reticular formation (RPRF) using carbachol, flavoxate and propiverine, and by analysis of amino acid levels in the lumbosacral cord.

MATERIALS AND METHODS

A total of 82 female rats were anesthetized with urethane. Under isovolumetric conditions physiological saline, carbachol, flavoxate or propiverine was injected into the RPRF or intravenously. Changes in bladder activity and amino acid levels in the lumbosacral cord were examined.

RESULTS

Injection of carbachol or flavoxate (0.3 microM each) into the RPRF abolished bladder contraction but there was no change after injection of physiological saline or propiverine. Intravenous injection of flavoxate or propiverine (0.1 to 10 mg/kg each) inhibited bladder contraction. Amino acid analysis revealed that injection of carbachol into the RPRF increased glutamate and glycine levels in the lumbosacral cord, while injection of flavoxate into the RPRF or intravenously caused an increase in glycine the lumbosacral cord. Injection of propiverine into the RPRF or intravenously did not influence lumbosacral cord amino acid levels.

CONCLUSIONS

These results suggest that the RPRF has an important role in the inhibition of bladder contraction and carbachol or flavoxate can activate descending RPRF neurons and inhibit bladder contraction via spinal glycinergic neurons.

Effects of two atypical neuroleptics, olanzapine and risperidone, on the function of the urinary bladder and the external urethral sphincter in anesthetized rats

BACKGROUND

A previous report showed that the atypical neuroleptic clozapine resulted in marked changes in urodynamic parameters and greatly inhibited the activity of the external urethral sphincter in anesthetized rats. Such findings may help explain the high incidence of urinary disturbances reported during clozapine therapy. In an effort to extend our observations to other atypical neuroleptic agents, the present study investigated the effects of two newer atypical antipsychotics, olanzapine and risperidone, on the bladder and external urethral sphincter during cystometry in anesthetized rats.

RESULTS

At a dose of 0.1 mg/kg (i.v.), olanzapine decreased the micturition volume and increased the residual volume. In addition, olanzapine decreased the expulsion time and the amplitude of the high frequency oscillations observed during the expulsion phase. Larger doses (1 mg/kg) had a greater effect. Olanzapine also reduced the activity recorded from the external urethral sphincter, and the bursting observed during the expulsion phase was abolished by 1.0 mg/kg. Risperidone had similar effects although the maximal effects were smaller than those observed with olanzapine. The amplitude of bladder contractions elicited by electrical stimulation of the pelvic nerve was reduced by olanzapine but not risperidone suggesting a possible anti-muscarinic peripheral effect of olanzapine.

CONCLUSIONS

Olanzapine and risperidone significantly altered several voiding parameters and decreased the activity of the external urethral sphincter in the anesthetized rat. We propose that these effects are due to the central action of these drugs and not to peripheral effects. These findings may explain some of the clinical reports of urinary incontinence with risperidone and may predict similar occurrences with olanzapine therapy.