Compounds of the formula I:or a pharmaceutically acceptable salt thereof, wherein, R1 is optionally substituted tetrazolyl, R2 is optionally substituted phenyl, optionally substituted pyridinyl or optionally substituted thienyl, and R3, R4, R5 and R6 are as defined herein. Also provided are methods of using the compounds for treating diseases mediated by a P2X3 and/or a P2X2/3 receptor antagonist and methods of making the compounds.
