Licences should never be regarded as immutable. Ideally, they should be reviewed at, say, five-year intervals. However, many national authorities do not have the capacity to undertake this task, particularly for as long as they remain engaged in the initial review of provisionally licensed products. In these circumstances many products fall to review on an ad hoc basis. Sometimes this is inspired by recently generated concern regarding safety. More frequently, a product attracts attention because the licence-holder has altered the formulation in some way - by changing, for instance, the source of the starting materials, the nature of the excipients, the route of synthesis of an active ingredient, or the claims made in labelling and promotional material. The precise circumstances in which licence-holders are required to apply for variations in a product licence differ from country to country. These circumstances should be clearly defined in all product licence documents, including provisional licences.

Licence-holders should be required, in all circumstances, to inform regulatory authorities immediately of unanticipated adverse effects that could possibly be associated with a licensed product and that might call for restrictive licensing action or the withdrawal of the product licence.