Amide derivatives of 1,4 di-substituted piperidine compounds of the formula (I) or a pharmaceutically acceptable salt, ester or solvate thereof, wherein R1 is optionally substituted cycloalkyl, cycloalkylalkyl, aryl, arylalkyl or heteroaryl; R2 is H, alkyl, or optionally substituted cycloalkyl, cycloalkylalkyl, heterocycloalkyl, bridged cycloalkyl, or bridged heterocycloalkyl; R3 is alkyl or -CH¿2?OH; and R4 is H or alkyl; are muscarinic antagonists useful for treating cognitive disorders such as Alzheimer's disease. Pharmaceutical compositions and methods of preparation are also disclosed.