sentences:  When physicians qualify for the waiver, they are given a second DEA number (i.e., in addition to the standard DEA prescribing number).This number begins with 'X', prompting the common nickname 'X-waiver'.Once prescribers obtain the waiver, they may treat up to 30 patients with buprenorphine-- following recent federal changes described below, they can request to increase their patient panel sizes after they have had a waiver for one year.