On Thursday, the regulator said drug companies would be forced to pay a total of £260 million ($360 million) in fines for engaging in prohibited practices.

Firms, including Accord Healthcare, Allergan Plc, Intas Pharmaceuticals, and Waymade Plc, were deemed to have contravened market rules, taking part in activities including paying off their competition, increasing the price of drugs when acting as the sole provider, and buying potential rivals to keep them out of the market.

The case relates to the supply of hydrocortisone tablets to Britain’s National Health Service (NHS). The CMA said the price of the life-saving hydrocortisone tablets, which treat adrenal insufficiency, including life-threatening conditions such as Addison’s disease, had risen by over 10,000%. The watchdog said the prices charged to the NHS were “excessively high.”

CMA CEO Andrea Coscelli said it was one of the most serious abuses identified in recent years. “Our fine serves as a warning to any other drug firm planning to exploit the NHS,” Coscelli said in a statement, adding that the extortionate prices reduced the money available for patient care.

The CMA wrote that, in one case, the NHS was being charged over £80 for a single pack of tablets that had previously cost less than £1. The case relates to practices undertaken between 2008 and 2018.

The firms fined have yet to comment on the matter.