SOARING price tags on some generic prescription drugs are forcing GPs to shift patients onto cheaper medications which may be less effective, a leading doctor has warned.

John Ip, a Paisley GP and medical secretary of the BMA’s Glasgow Local Medical Committee, said he had seen the cost of one long-standing antidepressant rocket 27-fold in the past four years, from less than £6 to £154 per packet.

Dr Ip said the problem was mostly affecting generic medicines - those no longer covered by a patent preventing competitors from manufacturing copies.

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He said: “In everyday practice we’re seeing certain medications that have increased in price phenomenally, way beyond what would be reasonable inflationary increases.”

Pharmacists in Scotland are also said to be struggling more than ever with shortages of some drugs used by the NHS, with the problem being blamed on a worldwide reduction in the the number of manufacturing sites and a drop in the value of Sterling driving the UK to export more drugs.

Dr Ip said he had noticed that doxepin, an antidepressant prescribed to patients with trouble sleeping, had gone from £5.71 in 2013 for a packet of 20 50 mg tablets to £154.

He said: “That’s a price increase of 27 times. If a patient is getting that every month, then the yearly cost for that medication - without any change in the patient - has gone from £68 a year per patient to over £1,800. These are not state of the art cancer treatments to do with saving lives or extending lives. This is a drug that has been around for decades, so drug companies can’t reasonably say that they are trying to recoup the cost of research.

“It’s quite an old fashioned drug, it’s not normally used as a frontline treatment for younger patients, but there is certainly a sizeable number of older patients who may have been on this for a long period of time.

“Sometimes we can switch patients to a different drug, but the one they are on might be the best medication for their condition. Trying to wean them off it and start something else on the basis of cost is really unfair on patients.

“If it can be done safely, that’s fine, but some patients can’t be switched and just trying to alter their medications can cause problems.”

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Dr Ip said an antibiotic called nitrofurantoin which is commonly used to treat urinary tract infections had gone from £3.66 for a packet of 30 50mg tablets in 2013 to £15.42. Although the price hike was less extreme, he said it arguably had a bigger impact on GP surgeries’ budgets because it was prescribed so often. Meanwhile, a 300ml bottle of nitrofurantoin as a sugar-free solution now had a price of £446.

“For the NHS to be paying near enough £450 for a bottle of antibiotic is phenomenal,” said Dr Ip.

Individual GP surgeries have an annual drugs budget, which is set by their local health board and usually based on historical spend. While GPs are under pressure to come in as close to budget as possible each year, price hikes ultimately push up the overall NHS drugs bill which came in at just under £1.6 billion in 2014/15.

Aileen Bryson, interim director for Scotland at the Royal Pharmaceutical Society, said she “could give a list as long as my arm” of drugs where demand was outstripping supply.

She said: “Medicines shortages are a big issue across the board. Pharmacists could be spending up to a day a week in some cases trying to source medicines for people because there is a shortage of a particular one.

“The list changes every week and every month. But of course, when things are short the manufacturers who do have them can put the price up.”

Ms Bryson said there was “definitely more of an issue” with generic drug shortages and price hikes in recent years.

She added: “The shortages are a global problem because traditionally we would have had production plants all over Europe, America and so on, but now there might only be plants in India and China because that’s the way manufacturing is going. So as soon as something goes wrong, there’s a much bigger impact on the supply chain.

“Even the foil packs that your medicine capsules come in - there are only two or three manufacturers of those in the world now.

“The other thing is that generics are priced in US dollars. Since Brexit, we’ve had a Pound that has dropped through the floor and that has immediately put the prices up as well. When the Pound was really strong against the Euro there wasn’t as much exporting of medicines. Traditionally, we’ve always imported medicines. Now there is more exporting of medicines.”

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In April, the UK Parliament passed legislation Health Services Medicinal Supplies (Costs) Act, which hands ministers the power to control the prices of generic drugs if it believed excessive prices were being charged. It followed a high-profile case which saw Pfizer and Flynn Pharma fined nearly £90 million by the Competition and Markets Authority for “excessive and unfair” pricing after they hiked the cost of an anti-epilepsy drug, phenytoin sodium, up 27-fold overnight.

Warwick Smith, director general of the British Generics Manufacturers Association, said the law would not make a "huge difference" to market-related price fluctuations. He stressed that the cost of generics in the UK overall is amongst the lowest in Europe, with prices falling on average by eight per cent over the last 10 years.

However, Mr Smith added: "The value of the pound is having an impact, because all of trading in medicines is done in Euros and Dollars. We've seen that beginning to have an impact after stocks that were already in the supply chain are being used up.

"On some specific products, particularly the older ones, we're also seeing situations where maybe the product was not that profitable in any case and because the regulator, not unreasonably, is asking for the production processes to be brought more up to date, that can have a cost.

"Ten years ago, national markets were the market. Now decisions around supply are being taken at a more regional - that is, European - level, and frankly, if products are a bit short companies would naturally divert the stocks they have to higher margin countries. Given that the UK is one of the lowest margin countries, they will still send stocks here - but we won't be at the top of the priority list."