Four South African drug manufacturers have been found by the country’s competition authority to have colluded in fixing bids for the supply of products to the tender system through which the state buys drugs for its hospitals and healthcare services.

One of the companies, Adcock Ingram, is one of the largest makers of generic drugs in South Africa and holds several licences from multinational pharmaceutical companies for the local manufacture—supposedly cheaply—of drugs used to treat HIV and AIDS. The three other companies, one of which assisted the authority and gave details of …