Generic Medicines Explained: Bioequivalence, INNs and Why Generics Cost Less

A generic medicine contains the same active ingredient, in the same strength and dosage form, as an originator (brand-name) product whose patent has expired. Generics account for the large majority of prescriptions dispensed worldwide — and understanding how they are approved explains why they can be trusted at a fraction of the originator’s price.

The active ingredient and the INN

Every active ingredient has an International Nonproprietary Name (INN) assigned by the World Health Organization — for example, paracetamol, amoxicillin or atorvastatin. Brand names differ by company and country, but the INN is the same everywhere, which is why searching by active ingredient is usually the most reliable way to compare products.

What bioequivalence means

A generic does not repeat the originator’s full clinical trial programme. Instead, the manufacturer must demonstrate bioequivalence: that the generic delivers the same active ingredient into the bloodstream at the same rate and extent as the reference product, within tight statistical limits (typically 80–125% for the key pharmacokinetic measures).

Because the active ingredient’s safety and efficacy were already established by the originator’s trials, bioequivalence plus proof of manufacturing quality is scientifically sufficient. This is the position of essentially every major regulator, including the FDA, EMA and SAHPRA.

Why generics are cheaper

Generic manufacturers do not carry the cost of discovery research or the original clinical trials, and competition between multiple generic makers drives prices down further. When several generics of the same molecule are on the market, prices commonly fall by 80% or more relative to the pre-expiry brand price.

Generic substitution in South Africa

South African law actively encourages generic use: under the Medicines and Related Substances Act, pharmacists are generally required to inform patients of the availability of a cheaper generic equivalent and to offer substitution, unless the prescriber has expressly forbidden it or the product appears on a non-substitutable list.

Because every registered product in South Africa has a regulated Single Exit Price, comparing the SEP of an originator and its generics is straightforward — the Medicine Price Registry publishes them all, and you can compare prices for any molecule using the HealthSA search page.