The path from initial laboratory discovery to becoming available on the NHS electronic prescription service to collect from local pharmacies is a slow process that does not often go through the path of least resistance.
The drug discovery process often takes over a decade and costs billions of pounds, incorporating a range of laboratory tests and clinical trials that ensure that any medication a GP
or community pharmacist prescribes is safe, effective and suitable for the purpose.
During that time, many drugs changed fundamentally in terms of dosage, compound, ingredients and even purpose, the latter of which led to a process known as drug repositioning.
Medicines Repositioning allows for medications approved on safety grounds to be reused to treat other conditions they were best suited for, with one of the most notable examples being how thalidomide went from being a disastrous treatment for morning sickness to being at one point the front-line treatment for leprosy.
However, a rare and particularly notable example of this is when a medicines is repositioned and becomes widely used for another purpose before later research suggests that it could be used for its initial condition in the first place.
Despite being unusual, it has happened more often than you might expect, usually with a particularly interesting story behind it.
Sildenafil Medicines
Aside from thalidomide, arguably the most famous example of drug repositioning is sildenafil, but unlike the former, the medication most famously branded as Viagra did end up becoming a heart medication.
Initially discovered in the mid-1980s at Pfizer’s UK facility in Sandwich, sildenafil was initially seen as a promising treatment for angina, reducing chest pain by increasing the flow of blood around the heart as an effective vasodilator.
Unfortunately, an early clinical trial suggested that it did not have a lot of effect on angina symptoms, but what became far more notable was not what it could not do but what was seen at the time as one of its major side effects.
The rest is relatively well-known history; it was repositioned as a cure for erectile dysfunction and became a front-line sexual health treatment at a time when its only effective alternatives were injections or vacuum pumps.
However, it has since become used as a heart medication, with lower doses used to treat pulmonary arterial hypertension using a similar active effect as the one that made it so popular in the first place.
There are quite a few options when it comes to hypertension treatments and typically if someone with hypertension is prescribed medication it takes the form of angiotensin-converting enzyme (ACE) inhibitors or angiotensin-2 receptor blockers (ARBs) depending on the circumstance.
However, having sildenafil as an option brings the medication full circle.
Topiramate Medicines
A prescription medication used primarily to treat epilepsy, topiramate was originally developed as a tablet to help treat hypoglycemia, a symptom of diabetes.
However, after 17 years of tests, topiramate was finally sold as an anti-epilepsy treatment in 1996, and like many cases of drug repositioning, the original exploration of its use in treating diabetes was largely abandoned.
Whilst there may have been potential for its use, there were other possible avenues, and what matters in clinical trials is not its effectiveness compared to a placebo, but its effectiveness compared to the current front-line treatment.
It was later adopted as a prescribed medication to tackle certain forms of migraines in 2004, but after a decade of use as an antiepileptic medication, topiramate started to garner attention again
as a potential treatment for certain diabetic symptoms.
It has also been combined with phentermine as a prescription weight loss medication prescribed for some people with type 2 diabetes.
The latter treatment, branded Qsymia, has been seen as a redeeming moment for phentermine as well, given that it is primarily associated with the failed, withdrawn weight loss medications Fen-Phen in the 1990s.
Lysergic Acid Diethylamide
A particularly unusual example of repositioning and return, lysergic acid diethylamide was first synthesised in 1938 and after some rather infamous accidental doses of the psychiatric medication, there was a hope to creator Albert Hoffman that it could be used to help treat mental health conditions.
It would be used briefly to help with post-traumatic stress disorder, but this would not last.
Lysergic acid diethylamide is of course better known as LSD, and became somewhat infamous for its effect on the counterculture movement in the 1960s as a regularly used recreational drug.
It was made illegal in the UK in 1966 and it has been a Class A drug ever since. However, there have been some studies looking into its potential use in highly controlled environments as a psychiatric drug, but this has not as of 2024 translated into approved medical treatments.
Frequently Asked Questions
A repurposed medicine is a drug that was originally developed or approved for one condition but has later been found to be effective for treating another. Repurposing allows existing medicines to benefit more patients while reducing the time and cost of developing new treatments.
Yes. In many cases, a repurposed medicine continues to be prescribed for its original approved use as well as its newer indication. Whether it is suitable depends on your individual medical needs and your healthcare professional’s advice.
Researchers may discover that an existing medicine has additional benefits beyond its original purpose. Repurposing can provide patients with new treatment options more quickly because the medicine’s safety profile is already well understood.
Repurposed medicines must still undergo appropriate clinical evaluation and regulatory approval for any new indication. Your prescriber will consider the potential benefits and risks before recommending a repurposed medicine for your condition.