Compounds of formula (I) and pharmaceutically acceptable salts, esters, amides, or radiolabelled forms thereof, wherein A, R1 and R2 are as defined in the specification, are useful in treating conditions or disorders prevented by or ameliorated by voltage-gated sodium channels, e.g., Nav1.7 and/or Nav1.8. Methods for making the compounds are disclosed. Also disclosed are pharmaceutical compositions of compounds of formula (I), and methods for using such compounds and compositions.