Provided herein are compounds of formula (I): or pharmaceutically acceptable salts, solvates or prodrugs thereof or mixtures thereof, wherein Z1, Z2, X1, X2, X3, R1, R2, R3, R4, m and n are defined herein. Also provided are pharmaceutically acceptable compositions that include a compound of formula I and a pharmaceutically acceptable excipient. Also provided are methods for treating an FAAH-mediated disorder comprising administering to a subject in need thereof a therapeutically effective amount of a compound or composition of the present invention.