Effects of clonidine (Catapresan) on urethral pressure

Effects of clonidine (Catapresan) on urethral closure pressure profile were investigated in five patients with minor urologic complaints. Plasma norepinephrine was measured as an index of sympathetic nervous activity. Intravenous injection of clonidine resulted in a pronounced fall in maximum urethral pressure. Plasma norepinephrine concentration decreased as expected. There was a statistically significant correlation between changes in plasma norepinephrine and urethral pressure after clonidine. These findings are discussed in relation to the known effects of alpha-adrenoceptor blocking drugs on urethral pressure. Clonidine may be useful in the treatment of some patients with functional infravesical obstruction.