A lot of pharmaceutical professionals have confusion between FDA Form 483 and Warning Letters. Both of these are issued by Food and Drug Administration (FDA) after a regulatory inspection of the manufacturing facility.
Form 483 is used by the FDA to communicate potential regulatory problems, while a warning letter is an escalation of this notice. A warning letter is far more serious than a 483 observation. A Form 483 is issued by the inspection team alone whereas a Warning Letter is issued from a higher level FDA official or officials. Warning letters usually result from multiple lacking responses to issued 483s, or other issues much more serious that require immediate attention/escalation.
Form 483s or Warning Letters can be very expensive resulting in thousands or even millions of dollars in costs for some companies. If the issues are systemic, Form 483’s or a Warning Letter can trigger training, redesign, process implementation, and other measures.
References : Greenlight Guru, Pharma Treasures, Pharmaceutical Guidelines