A Times investigation in 2016 exposed how several manufacturers had taken advantage of a loophole in NHS pricing rules to significantly increase the price of dozens of commonly prescribed drugs by up to 12,500 per cent. The government passed legislation in April last year to end the practice by giving the health secretary powers to impose a lower price for these generic drugs if taxpayers were being ripped off.

However, the government has failed to use these, with a Times analysis revealing that the NHS is continuing to spend more than £200 million a year on the extra costs created by the hikes.

Just 19 of the 70 drugs identified by this newspaper two years ago have undergone significant price reductions, amounting to about £150 million a year in savings to the NHS. The total extra cost of the price hikes across all 70 medicines was £370 million a year in 2016, meaning that at least £200 million is still being overspent annually. The figures are approximate because prescription data is not yet available for the second half of 2018.

The government has referred a number of cases to the Competition and Markets Authority (CMA), which has opened at least nine investigations. These cases have been stalled after Pfizer and another drug company won an appeal against a record fine for increasing the price of an epilepsy treatment. The CMA is seeking permission to appeal against that verdict.

One company previously exposed by The Times, Atnahs, increased the price of seven medicines for which it was the sole UK manufacturer by up to 2,600 per cent. These included 50mg capsules of doxepin, an antidepressant, which rose from £5.71 and now costs £154 a packet. Atnahs was able to increase prices by dropping the brand name of the products, which were all out of patent, and relaunching them under generic names. Branded generics are subject to a profit cap but the NHS does not limit the price of unbranded generics. More than two years later, all seven medicines are at the same inflated prices.

Another firm, Concordia International, increased the cost of eye drops from £2.09 to £29.06 and has kept them at this level since 2016. An antidepressant which increased from £9.57 to £353.06 after being acquired by the company has risen further still in the past two years and now costs £386.53.

A Department of Health and Social Care spokeswoman said that the overall spend on generic medicines went down compared to last year.”

A spokesman for Atnahs said the company’s pricing was “competitively benchmarked” and that it would adhere to any government guidance. Concordia International said it believed the generics system was working well and “the government may not see a need to use these prices controls”.

Case study

Melanie Woodcock, 47, credits the thyroid medication liothyronine with giving her a life. She used to take an alternative that left her “feeling sluggish, constant headaches, dizziness, nausea feeling all day, it even affected my vision, just a constant brain fog”.

“I wasn’t going out anywhere, I wasn’t living a life, I wasn’t going on holiday, I wasn’t doing anything because I didn’t have the energy,” she said.

When she first took liothyronine, a synthetic hormone known as T3, she said it “changed my whole outlook on life”. “I could think clearly I’d got a memory, my vision was better, I lost the achy joints,” she said. “No more living on Neurofen because I had headaches all the time and joint pain.”

Now doctors have stopped prescribing the drug after the price rose from 16p to £9.22 per tablet. The medicine only had one supplier for many years, but even though two companies have recently begun supplying it, the cost to the NHS has barely fallen.

Liothyronine is cheaply available in many European countries and after her prescription was stopped in July 2018, Ms Woodcock, a mother-of-two who lives in Banbury, Oxfordshire, turned to a “website that is aimed at bodybuilders for bulking up” which sells the drug at £31 a packet.

She said when she tried to go back to the alternative treatment, levothyroxine, she was hospitalised with violent illness and a headache so powerful she was unable to see.

Even the liothyronine she buys online has not solved the problem. “It’s not the same [as the NHS-prescribed version], I still feel sluggish, I still have a lack of energy. I’ve had to take several days off work.”

Ms Woodcock, who works in the security industry, said she couldn’t understand “how the government have allowed this to happen”.