A British parallel importer will buy the drugs in countries such as from EU, where wholesale prices are very much lower, and repackaging them for the home market. It's the same chemical compound, usually produced in the same factory; only the price is different.

Both categories are not only highly regulated but officially encouraged. The Government, after all, hardly wants to deter anybody who promises to reduce the NHS's drugs bill. It's the pharmaceutical giants that complain. They defend their patents until the last possible moment and argue that parallel importing diverts cash from the British science base. But they have never succeeded in eliminating the entrepreneurial opportunities. 

Before a parallel-traded product can be marketed,

either re-labelling in the local language or replacing the outer carton is required.

The judgement of the European Court of justice in Bristol-Myers Squibb vs. Paranova (Cases C-427/93, C-429/92 and C-436/93), which stated that the importer must give advance notice to the trademark owner of his intended sale

In order for an importer to do this without infringing trademark law, all five criteria set out by the European Court of Justice (ECJ) in the Bristol-Myers Squibb cases have to be met:

1. Any refixing or replacing of the original trademark must be necessary in order for the imported product to be marketed.
2. The original condition of the product inside the packaging is not affected.
3. The new packaging states who manufactured the product and who repackaged it.
4. The presentation of the repackaged product does not damage the reputation of the   trademark and its owner.
5. The trademark owner is given adequate prior notice before the repackaged product is put on sale and, on demand, is supplied with a specimen of the repackaged product.