(a)Duration of prescription requirement. Any drug limited to prescription use under section 503(b)(1)(B) of the act remains so limited until it is exempted as provided in paragraph (b) or (e) of this section. (b)Prescription-exemption procedure for drugs limited by a new drug application. Any drug limited to prescription use under section 503(b)(1)(B) of the act shall be exempted from prescription-dispensing requirements when the Commissioner finds such requirements are not necessary for the protection