Urinary bladder-selective action of the new antimuscarinic compound vamicamide.

1. The inhibitory action of vamicamide (FK176, (+/-)-(2R*,4R*)-4-dimethylamino-2-phenyl-2-(2-pyridyl)valeramide, CAS 132373-81-0) on the responses of various tissues to the cholinergic agonists, carbachol and McN-A-343 (4-[m-chlorophenylcarbamoyloxy]-2-butynyl-trimethylammonium chloride, CAS 55-45-8), was investigated in isolated tissue preparations. Vamicamide showed competitive antagonistic actions against all the preparations tested and its pA2 value for the urinary bladder was 6.82, which was higher than that for the atria (5.94) and almost the same as that for the vas deferens (6.90) and for the stomach (6.81). The pA2 values of oxybutynin hydrochloride (oxybutynin) and atropine sulfate monohydrate (atropine) were nearly the same in all the tissues tested. 2. Oral administration of vamicamide 0.1-1.0 mg/kg inhibited dose-dependently spontaneous bladder contractions caused by raising the intravesical volume in conscious rats. Inhibitory actions were also obtained with 0.32-3.2 mg/kg of oxybutynin or 0.0032-0.032 mg/kg of atropine, but the duration of action of oxybutynin was shorter than that of vamicamide or atropine. Vamicamide further inhibited bladder contractions in rats following intravesical administration of 0.05-0.5 mg/ml solution. 3. Vamicamide had no effect or only slightly inhibited spontaneous motility of the stomach and distal colon in conscious rats, as well as heart rate and salivary secretion in conscious dogs, after oral dosing with 3.2 mg/kg of the compound. Similar results were obtained with oxybutynin, excepting the occurrence of tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)