Pyridinyl amides as P2X3 and P2X2/3 inhibitors

A compound of formula I

• wherein:
• R1 is:
• pyridinyl substituted with methyl or halo at the 5-position;
• R2 is:
• hydrogen;
• or
• C1-6alkyl;
• R3 is:
• C1-6alkyl;
• hydroxy-C1-6alkyl;
• C1-6alkoxy-C1-6alkyl;
• halo-C16alkyl;
• C3-7cycloalkyl;
• heteroaryl which may be substituted once or twice with methyl;
• heterocyclyl;
• heterocyclyl-C1-6alkyl;
• or
• C3-7cycloalkyl-C1-6alkyl;
• or R2 and R3 together form a C3-7cycloalkyl;
• R4 is:
• hydrogen;
• C1-6alkyl;
• C3-7cycloalkyl;
• C3-7cycloalkyl-C1-6alkyl;
• or
• pyrimidinyl;
• R5 is:
• C1-6alkyl;
• C1-6alkoxy;
• C3-7cycloalkyl;
• C1-6alkoxy-C1-6alkyl;
• amino-C1-6alkyl;
• oxetanyl which may be substituted once or twice with C1-6alkyl;
• phenyl which may be substituted once or twice with a group or groups independently selected from C1-6alkyl, halo, halo-C1-6alkyl and C1-6alkoxy;
• thienyl which may be substituted once or twice with a group or groups independently selected from C1-6alkyl and C1-6alkoxy;
• furanyl which may be substituted once or twice with C1-6alkyl;
• thiazolyl which may be substituted once or twice with C1-6alkyl;
• oxazolyl which may be substituted once or twice with C1-6alkyl;
• isoxazolyl which may be substituted once or twice with a group or groups independently selected from C1-6alkyl and phenyl;
• pyrazolyl which may be substituted once or twice with C1-6alkyl;
• thiadiazolyl which may be substituted once with C1-6alkyl;
• tetrahydropyranyl;
• morpholinyl;
• piperidinyl which may be substituted with C1-6alkyl or acetyl;
• pyrimidinyl;
• or
• pyridinyl which may be substituted once or twice with C1-6alkyl;
• and
• R6, R7 and R8 each independently is:
• hydrogen;
• or
• halo.