In vivo and in vitro studies on the effect of sodium antagonists on the bladder in man and rat.

The effect of oral mexiletine and intravenous lignocaine was examined in elderly patients with urinary incontinence associated with detrusor instability. Lignocaine had no demonstrable urodynamic effect in 13 patients, but 12 out of 20 patients who completed the study with mexiletine benefited, 10 becoming dry. The incidence of side-effects was high. Since there was no associated urodynamic improvement on the drug, the clinical improvement was probably secondary to the toileting regime instigated in every case. The results of the in vitro experiments on 11 rat bladders supported this contention, since mexiletine caused contractions of the preparation, and increased the rate and magnitude of spontaneous activity. Acetylcholine, histamine and 5-hydroxytryptamine receptors were not involved in these contractions.