The present disclosure provides substituted piperidines or pyrrolidines having Formula IA: and the pharmaceutically acceptable salts and solvates thereof, wherein R1, R2a, R2b, R6, A, X, m and n are defined as set forth in the specification. In certain embodiments, Compounds of the present disclosure are useful for treating pain. The present disclosure is also directed to the use of Compounds of the present disclosure to treat a disorder responsive to blockade of one or more sodium channels.