Verapamil organic cation transport

Further clinical examples of potential stereoselective renal secretion of organic cations have been recently reported. A major metabolite of verapamil (D-617) is actively secreted by the kidney (59). Upon coadministration of dmetidine, the renal clearance of the S-D-617 isomer was significantly decreased, whereas the clearance of the R-D-617 metabolite was unaffected by dmetidine administration (59). Stereoselective renal secretion was suggested as the mechanism of this effect. However, it is not known if this metabolite is actually secreted by the organic cation transport system. The renal clearance of unbound S(+) disopyramide was... 

Saitoh, H., Aungst, B. J., Possible involvement of multiple P-glyco-protein-mediated efflux systems in the transport of verapamil and other organic cations across rat intestine, Pharm. Res. 1995, 12, 1304-1310. 

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