The present invention relates to a compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein: R2 represents hydrogen, halogen, C1-6 alkyl, C6-10 arylmethyl-, C2-6 alkenyl, C2-6 alkynyl or C3-6 cycloalkylmethyl-; and any of said C1-6 alkyl, C6-10 arylmethyl-, C2-6 alkenyl, C2-6 alkynyl or C3-6 cycloalkylmethyl- is optionally substituted with 1, 2 or 3 halogen atoms; and R3 represents hydrogen, fluorine or methyl; or R2 and R3 together with the carbon atoms to which they are attached form a benzene ring optionally substituted with 1, 2 or 3 substituents, which may be the same or different, selected from the group consisting of C1-6 alkyl, C2-6 alkenyl and C2-6 alkynyl. The compounds or salts modulate P2X7 receptor function and are capable of antagonizing the effects of ATP at the P2X7 receptor. The invention also provides the use of such compounds or salts, or pharmaceutical compositions thereof, in the treatment of disorders mediated by the P2X7 receptor, for example pain, inflammation or neurodegeneration.