Effects of Nifedipine on the Smooth Muscle of the Human Urinary Tract in Vitro and in Vivo

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Abstract
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 [norepinephrine] (0.1-3 .mu.g .cntdot. ml-1 prostaglandin [PG] F2.alpha. (1-10 .mu.g .cntdot. ml-1), and K (127mM), the bladder preparations by carbacholine (0.004-1 .mu.g .cntdot. ml-1), PG F2.alpha. (1-10 .mu.g .cntdot. ml-1), K (127 mM), and BaCl2 (3 mM), and the ureter preparations by K (127 mM), and BaCl2 (3 mM). Irrespective of the mode of activation, pretreatment with nifedipine (0.1 .mu.g .cntdot. ml-1) for 10 min. reduced the responses. Nifedipine also relaxed preparations contracted by the contractile agents used. In 19 female patients, aged 20-73 yr, undergoing investigation because of urgency and/or urge incontinence, simultaneous urethrocystometry at rest was performed before and after oral administration of 20-40 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 the bladder and urethra.