The Effect of Tamsulosin on the Resting Tone and the Contractile Behaviour of the Female Urethra: A Functional Urodynamic Study in Healthy Women
Introduction
Chronic urinary retention in young women as a part of a syndrome associated with polycystic ovaries has been described in 1988 by Fowler et al. [1]. Women affected by chronic urinary retention usually present with impaired detrusor contractility, bladder outflow obstruction or even with a combination of both problems. Since an abnormal electromyographic activity in the external urethral sphincter has been found, a functional bladder outflow obstruction by a non-relaxing or overactive sphincter mechanism is thought to be the underlying reason [2].
In these women treatment modalities basically rely on the intermittent self catheterisation, however the goal in these patients would be to restore voluntary voiding with tolerable amounts of residual urine. Sacral neuromodulation has been tried and was found to be effective to restore the ability to void voluntarily in many patients [3]. Although the injection of botulinum toxin into the external urethral sphincter has been shown to improve the ability to void in some women with urinary retention [4], a study in women with abnormal sphincter electromyography did not show a symptomatic benefit [5].
Only one study tried α-blockers in chronic urinary retention with some success [6], however a pharmacological treatment option to close the gap between catheterisation and invasive procedures would be of value for this patient population. There is now a considerable amount of experimental data from animal and human studies to show that α-blocking agents have the capacity to relax the urethral tone. The aim of this functional urodynamic experiment was to study the effect of the selective α1A-blocker tamsulosin on the urethral pressure in healthy human females and assessed first the resting urethral pressure and second the urethral contractility in response to magnetic stimulation of the sacral roots.
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Subjects and methods
The experimental protocol was approved by the local ethics committee. 11 healthy female subjects (mean age 24 years, range 20–29 years) gave a written informed consent and were included in the study. None of the subjects had a history of recurrent urinary tract infections, stress or urge urinary incontinence or was taking any medication known to influence the lower urinary tract. Immediately before and two days after the experiment, urine screening tests were done to exclude urinary tract
Results
The experimental procedure was well tolerated by all studied subjects. Each the baseline and the follow-up measurements took around 30 minutes to perform. Urine screening tests were all normal before as well as two days after the experiment. None of the subjects felt any pain or discomfort during single pulse magnetic stimulation. 4 out of the 11 studied subjects reported a light tiredness at the follow-up 6 hours after tamsulosin intake.
Discussion
To our knowledge this is the first urodynamic controlled study to show that the selective α1A-antagonist tamsulosin has a significant relaxing effect on the urethral tone in healthy females in vivo. Our data show clearly that the resting tone of the female urethra is lowered significantly while the contractility in response to as sacral magnetic stimulation is not influenced by the drug. The relaxing effect of tamsulosin on the urethra was significant in terms of mean urethral pressure and
Conclusion
These data show a significant relaxing effect of tamsulosin on the resting urethral tone in healthy females in vivo. These results may suggest tamsulosin as a new pharmacological approach to treat urinary retention due to overactive or non-relaxing urethra in women.
Editorial Comment
C. Chapple, Sheffield, United Kingdom
This study has evaluated the effect of tamsulosin on urethral pressure in 11 young asymptomatic females. It is clear that tamsulosin reduced the mean
Acknowledgements
The authors are grateful to Ms. Nicole Honegger for excellent technical assistance and Mr. Huub van Hedel for statistical counselling. This study was supported by the Swiss National Foundation (Grant No. 32.52562.97), the European Community (Grant REBEC QLG5-CT-2001-00822) and a research grant from Boehringer Ingelheim.
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