Effects of nifedipine on the smooth muscle of the human urinary tract in vitro and in vivo.
Smooth muscle preparations of the urethra, bladder, and ureter were obtained from patients undergoing operations for various urological disorders. The urethral preparations were contracted by noradrenaline (0.1-3 microgram . ml-1), prostaglandin F2alpha (1-10 microgram . ml-1), and potassium (127 mM), the bladder preparations by carbacholine (0.004-1 microgram . ml-1), prostaglandin F2alpha (1-10 microgram . ml-1), potassium (127 mM), and barium chloride (3 mM), and the ureter preparations by potassium (127 mM), and barium chloride (3 mM). Irrespective of the mode of activation, pretreatment with nifedipine (0.1 microgram . ml-1) for 10 min. reduced the responses. Nifedipine also relaxed preparations contracted by the contractile agents used. In 19 female patients, aged 20 to 73 years, undergoing investigation because of urgency and/or urge incontinence, simultaneous urethrocystometry at rest was performed before and after oral administration of 20 to 40 mg nifedipine. Bladder capacity and residual urine were also determined. Nifedipine did not affect the pressures within the bladder and urethra, nor did it increase the bladder capacity. However, after nifedipine intake there was a statistically significant increase in residual urine. The results suggest that nifedipine can inhibit contractile activity induced by drugs with different modes of action; the drug does not affect the tone in bladder and urethra.