Provided is a method of treating or lessening the severity of pain in a subject, comprising administering to the subject a compound of formula (I), defined as described herein, or a pharmaceutically acceptable salt thereof.本發明提供一種治療個體之疼痛或減輕其嚴重程度之方法,其包含向該個體投與如本文所述定義之式(I)化合物或其醫藥學上可接受之鹽。