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The story of the history of Viagra is a fascinating one, from a potential drug to help treat angina to the primary treatment for ED, and then to a drug used to help treat a range of heart issues such as pulmonary hypertension.

Part of the reason for this is major advances in medical research, but it also showcases an important part of medical research where existing medications can be used to treat other conditions. This is a process known as drug repurposing or repositioning.

Here is the story of how cheap sildenafil was repurposed from a heart medication to a leading treatment for ED and then back again over twenty years of research.

What Is Drug Repositioning?

Pharmaceutical research involves initial theories and many stages of early research in synthesising compounds to try and treat various medical treatments. Once a potential candidate is found, it is tested in clinical trial subjects to ensure they are both safe and effective.

The safety aspect, in particular, looks at potential side effects, and it is here where potential alternative uses for medications are often found.

Using an existing medication is often desirable because it reaches the market faster with less clinical trial steps as the medication has already proven to be safe, and because it is already bring produced it can take less time for existing manufacturers to make a version designed to treat a different condition.

Whilst there have been several examples of drug positioning over the years, such as CBD for certain types of epilepsy and thalidomide for leprosy and cancer (under very specific conditions), sildenafil’s story is the most well-known case study into drug repositioning.

When Failure Begets Success

Sildenafil was initially developed to treat angina and coronary artery disease in the 1980s by Pfizer, however, its success was somewhat borne out of failure.

During its Phase I clinical trials (which primarily screen for safety), sildenafil was found to cause erections as what was at that point considered a side effect, however, due to the nature of clinical trials it was not considered at that point a treatment for erectile dysfunction.

That only came after sildenafil failed its Phase II clinical trials (which show the effectiveness of the drug against placebo), which left Pfizer with a heart medication that was not effective enough at treating the conditions it was meant to treat.

At this point, the research could have been abandoned, however, because of the initial clinical trials, Pfizer decided to see if it could be used as a cure for erectile dysfunction, which at the time of the Phase 2 trials required either surgery or injections to treat.

The rest, as they say, is history. However, due to its massive success, other medical uses for sildenafil, from pulmonary hypertension to stopping pulmonary edemas at high altitude, were found through extensive medical research.

The story of sildenafil and other repurposed drugs highlights that potential medical solutions can come in all directions, from all-new discoveries to the side effects of seemingly failed experiments.