Methenamine-hippurate and bacteriuria in the geriatric patient with a catheter.

Oral treatment with methenamine-hippurate (MH) in patients with an indwelling catheter has been found to reduce the need of frequent catheter exchange and the number of symptomatic infections. Bacteriuria, however, persists during MH treatment. The hypothesis that the therapeutic effect is due to a reduction in the number of bacteria, or a change in the pattern of strains was tested in a crossover study (2 x 6 weeks). MH treatment, 1 g twice daily, was compared to control periods in 52 patients. The majority of quantitative and qualitative bacterial cultures at 2-week intervals yielded 2--4 strains. Of the bacterial isolates, 50% were found on 4--6 occasions out of 6 possible. MH treatment had no significant influence on the pattern of various strains. A 30% decrease in the mean total bacterial count during MH treatment did not reach statistical significance (p approximately 0.07). It is suggested that prevention of catheter complications during MH treatment may be due to a physiochemical action on salt formation rather than a direct antibacterial effect.