The age is determined by the drug regulating organization of each country. In the US it is determined by the FDA. Each country may have different rules and procedures for determining drug safety, both in general and for children. In the US, Novartis has provided sufficient testing results to get FDA approval. In other countries with differing standards, Novartis has not yet provided sufficient information to get approval for use by younger patients. As further evidence is gathered by Novartis, you can expect the age limit to be reduced in many countries regarding the use of exjade, as long as these trials demonstrate that the drug is safe for long term use.