Newly licensed drugs

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Abstract
Firstly, the licensing process cannot define uncommon adverse effects. It is easier to measure common therapeutic benefits than rare, but important, reactions. The numerical problem is daunting. If n patients have been treated, and none has suffered a particular adverse effect, then we can be 95% sure that the true incidence of that adverse effect is between 0/n and 3/n.1 Licensing decisions are based on trials involving on average around 1500 patients,2 so at the time of licensing, a serious reaction that affects as many as 1 in 500 patients could be undetected, and undetectable. Britain's Committee on Safety of Medicines asks for “yellow card” reports of any reactions to newly licensed medicines, marked with an inverted black triangle. A post marketing surveillance scheme, which monitors prescriptions and adverse events, exists only in general practice. Both schemes rely on the good will of prescribers rather …