The approval decision
When trials finish, the company submits everything — every dose, every adverse drug reaction, every manufacturing detail — to a regulator (such as the FDA or EMA). Drug approval is never a verdict of 'totally safe'. It is a judgement that, for a defined use, the expected benefits outweigh the known risks. The label that results spells out who should take it, at what dose, and the warnings that must travel with it.
Generics and bioequivalence
A new drug is sold under a brand name and protected by patents for a number of years, letting the company recover its development costs. When the patent expires, other makers may sell a generic drug under the shared generic name. A generic does not repeat the full trial programme — that would be wasteful and unethical, since efficacy is already proven. Instead it must demonstrate bioequivalence: that it delivers the same active ingredient into the bloodstream at essentially the same rate and amount.
Bioequivalence test (typical):
Give brand vs generic to volunteers; compare blood-level curves.
Two key measures must match closely:
Cmax = peak blood concentration
AUC = total drug exposure over time
Pass rule: 90% confidence interval of
(generic / brand) for Cmax and AUC must fall
within 0.80 - 1.25 (i.e. within +/- 20%).
Same active ingredient + same Cmax & AUC = same clinical effect.Pharmacovigilance: the watch never ends
Even the biggest Phase III trial studies thousands of people for months. Once a drug reaches millions over years, rarer and slower harms appear. Pharmacovigilance is the ongoing science of monitoring approved medicines: clinicians and patients report any suspected adverse drug reaction, and these signals — together with Phase IV data — are pooled and analysed worldwide.
If a serious pattern emerges, regulators can add or strengthen a warning, restrict who may use the drug, or — in the worst case — order a drug recall that pulls it from the market. This is the system honestly admitting that approval is a *best judgement on the evidence so far*, not a permanent guarantee.