If, in the opinion of the Central Government, public interest requires that the advertisement of any specified drug or class of drugs ¹[or any specified class of advertisements relating to drugs] should be permitted, it may, by notification in the Official Gazette, direct that the provisions of sections 3,4,5 and 6 or any one of such provisions shall not apply' or shall apply subject to such conditions as may be specified in the notification to or in relation to the advertisement of any such drugs or class of drugs ¹[or any such class of advertisements relating to drugs].