define specific difference between FDA, MHRA, PICs and PDA guidelines
core of question not understood, regulatory authorities like US FDA, Indian FDA, MHRA, WHO, TGA etc. are working for respective country and region. they are govt. authorities and providing cGMP requirement in the form of Guidelines. second PICs, ICH, PDA these are authorities working to harmonise, improvements for industrial practices. summery, finding and discussion they are publishing as guidelines and articles.
@vaibhav is right Guidelines provided by international authorities as WHO, ISO, ICH, PIC/s are mandatory and must be followed by every country but other guidelines by USFDA, MHRA, TGA, MCC etc are country specific and must be followed by respective country.