(Bloomberg) -- Pfizer Inc. and Flynn Pharma Ltd. were fined a combined £70 million ($83.6 million) after UK antitrust authorities said the firms charged “unfairly high prices” for a drug used to control epileptic seizures.

Pfizer was fined £63 million and Flynn Pharma was fined £6.7 million, the Competition and Markets Authority said Thursday. The companies exploited a loophole by de-branding the drug known as Epanutin, so that its price wasn’t regulated the same way as other branded drugs. Over a four-year period, Pfizer charged prices between 780% and 1,600% higher than previously.

The UK’s National Health Service had no choice to pay the inflated final price, the CMA said.

“These firms illegally exploited their dominant positions to charge the NHS excessive prices and make more money for themselves – meaning patients and taxpayers lost out,” Andrea Coscelli, the CMA’s chief executive officer said in the statement.

The decision follows a 2020 ruling by the Court of Appeal that decided the CMA’s previous investigation was “insufficiently deep or intense.” The CMA had initially imposed what was at the time a record penalty of £84.2 million on Pfizer but was forced to reopen the probe.

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