Effects of disopyramide on detrusor muscle contraction: in vitro experiment and report of 3 cases with disopyramide-induced urinary retention

Cisapride reverses the anticholinergic effect of disopyramide on the isolated guinea-pig urinary bladder

The present investigation aims to examine whether the prokinetic agent cisapride is able to reverse disopyramide's anticholinergic effect on the isolated guinea-pig urinary bladder. Acetylcholine, at concentrations ranging from 10(-7) to 10(-3) M, produced a stimulatory effect on the urinary bladder (pEC(50) value=5.1). Disopyramide competitively antagonized the contractile effect of acetylcholine with an ID(50)=4.4 x 10(-6) M. Although cisapride by itself had either no intrinsic contractile action or a modest effect on the urinary bladder, at concentrations ranging from 3 x 10(-7) to 10(-6) M, it significantly reversed the above inhibitory effect of disopyramide, and produced a parallel leftward shift of the concentration-response curve for acetylcholine in the presence of disopyramide. The pEC(50) values for acetylcholine in the presence of 3 x 10(-6) M and 10(-5) M disopyramide were 4.7 and 4.2, respectively, while in the presence of 10(-5) M disopyramide, after pretreatment with 5 x 10(-7) M cisapride, the pEC(50) value for acetylcholine was 4.6. It is concluded that cisapride is effective in reversing the anticholinergic activity of disopyramide on the isolated guinea-pig urinary bladder, probably by facilitating cholinergic neurotransmission.

Inhibition of isolated rat and human detrusor muscle contraction by disopyramide

1. The aim of this study was to investigate the effect of in vitro and in vivo disopyramide treatment on human and rat isolated detrusor muscle contractile response. Muscle strips were suspended in an organ bath chamber containing Kreb's solution at 37 degrees C aerated with 95% oxygen and 5% carbon dioxide. 2. Disopyramide antagonized significantly the contractile response of isolated human detrusor muscle to carbachol stimulation, shifting the concentration-response curve to the right in a parallel manner. The pA2 for competitive inhibition was estimated to be 6.4 with a slope of 0.64 for disopyramide. 3. Rat detrusor muscle contractile response to electrical field stimulation (EFS) was inhibited by 28% (P < 0.01) after in vitro administration of disopyramide (7.5 x 10(-6) M). Disopyramide had no effect on the atropine-resistant component of the response to EFS or on spontaneous contractions of isolated rat detrusor muscle strips. The concentration-response curve to carbachol was competitively antagonized by disopyramide with a pA2 of 6.3 and a Schild curve a slope of 0.85. 4. Disopyramide (7.5 x 10(-6) M) had no effect on rat detrusor contractile response to low concentrations of KCl but at high concentrations contraction was reduced significantly by 16% (P < 0.01). 5. In vivo treatment of rats with disopyramide for 8 days or with a single dose had a significant inhibitory effect on the contractile response of detrusor muscle strips. 6. In conclusion, disopyramide had a significant anticholinergic effect on isolated human and rat detrusor muscle contraction.