A method of antagonizing P2X3 and/or P2X2/3 receptors or treating a disease misregulation of P2X3 and/or P2X2/3 receptors treating a patient with a compound of formula I wherein R1, R2, R3, R4, R5 and R6 are as defined herein, 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 associated with the P2X3 and/or a P2X2/3 receptor antagonist and methods of making the compounds.