Alteration of drug transport.

1. Digoxin-quinidine or verapamil

- Digoxin to verapamil or quinine resulted high serum concentration. Both can
inhibit the p-glycoprotein so increase absorption, decrease elimination, and
high concentration of digoxin.

2. Loperamide-P-glycoprotein

- Antidiarrhoeal agent loperamide unlikely cause nervous system adverse events.
P-glycoprotein prevents it from crossing BBB and penetrates to CNS