Good Manufacturing Practice is a series of regulations, practices and philosophies that simultaneously constrain and enable the manufacturing of pharmaceuticals and medicines that are subject to widespread marketing.
They exist primarily to protect the public from the consequences of unconstrained or unregulated medicinal manufacturing. Many examples exist from history of tragedies, widespread and local, were unfortunate people died of suffered serious harm as a result of poor or uncontrolled manufacturing.
Good Manufacturing Practice, when implemented correctly should ensure that medicinal products are made to a standard that ensures they are safe if used correctly, represent the highest standards of product quality and do exactly what they say on the label. Every. Single. Time