The effects of norephedrine and bethanechol on the human urethral closure pressure profile

In twelve women with urinary stress incontinence simultaneous measurements were made of the intravesical and intra-urethral pressures, including the urethral closure pressure profile (UCPP), before and after oral administration of norephedrine or subcutaneous injection of bethanechol. The investigations were carried out at various bladder volumes in the supine position and at bladder volume 300 ml in erect position. Irrespective of bladder volume or body position, norephedrine caused a statistically significant rise in maximum urethral pressure (MUP) and in maximum urethral closure pressure (MUCP). The intravesical pressure was not affected. After intravenous injection of phentolamine, MUP and MUCP fell to levels below the original readings, but here too the intravesical pressure was unaffected. Injection of bethanechol was followed by significant increase in the intravesical pressure, irrespective of bladder volume or body position. There were no consistent changes in the intra-urethral pressure. As a consequence of the rise in intravesical pressure, however, the MUCP fell slightly. The results of the study suggest that orally administered norephedrine causes an increase in the MUCP in women with stress incontinence of urine, an increase that may prove therapeutically useful. Bethanechol, in doses that significantly increased intravesical pressure, did not alter the intra-urethral pressure.