The US drugmaker faces a penalty of £84.2m, while Flynn Pharma will pay a £5.2m fine. The action follows after CMA found that the drug price was increased by up to 2,600% in September 2012.
Prior to this, Pfizer manufactured and sold phenytoin sodium capsules to UK wholesalers and pharmacies under the brand name Epanutin and the prices of the drug were regulated.
The price hike occurred after Pfizer transferred the UK distribution rights for the drug to Flynn Pharma.
The CMA also found that the price of the drug in the UK is many times higher than Pfizer’s prices for the same drug in any other European country.
The extraordinary price rises have cost the NHS and the taxpayer tens of millions of pounds, according to CMA.
CMA investigation case decision group chairman Philip Marsden said: “This is the highest fine the CMA has imposed and it sends out a clear message to the sector that we are determined to crack down on such behaviour and to protect customers, including the NHS, and taxpayers from being exploited.”
Pfizer, however, has disapproved the findings set out in the CMA decision and said it would appeal against the decision.
The American pharmaceutical manufacturer said that phenytoin capsules were a loss making product and the Flynn transaction offered an opportunity to secure an ongoing supply of an important medicine for patients with epilepsy, while maintaining continuity of manufacture.
In a statement, Pfizer said: "The ruling highlights real policy and legal issues concerning the respective roles of both the Department of Health and the CMA, in regulating the price of pharmaceutical products in the UK. Pfizer will seek clarity on these issues as part of the appeal process."
Phenytoin sodium capsules are currently used by an estimated 48,000 epilepsy patients in the UK to prevent and control seizures.
Image: Phenytoin sodium capsules are used in the treatment of epilepsy to prevent and control seizures. Photo: © Crown copyright.