Viagra – Is The Blue Pill Finally Losing Its Potency?

viagra 4pack pfizer

22 April 2020 marks D-Day for Viagra – Pfizer’s famous diamond-shaped blue pill – as it is set to lose out on market exclusivity in the United States. Having witnessed mind-boggling sales of the drug for two decades now, we take a look at the unconventional and perhaps controversial rise of Viagra. What lies in store for the little blue pill that never really harbored blockbuster dreams?

Sildenafil Citrate (Viagra)

In June 1993, scientists at Pfizer had identified a less-than-promising new treatment for hypertension and angina. They decided to push the drug candidate through to Phase I clinical trials, despite evidence suggesting that further drug development would likely result in failure. The compound was administered – in small doses – to a community of miners (mostly males) in South Wales, to see if the drug would be well tolerated once inside a human body. Instead, the participants in the trials awkwardly reported getting sustained erections in the evenings after taking the compound.

The as-yet-unnamed compound worked by inhibiting phosphodiesterase enzymes, which prevented it from breaking down a molecule in the body known as cyclic guanosine monophosphate (cGMP)1. cGMP could then work its magic by relaxing the smooth muscle that normally blocks blood flow into the penis, resulting in a sustained erection. At the time, there was no other drug approved for use that had this effect.

sildenafil viagra molecular structure
Chemical structure of sildenafil, the active compound in Pfizer’s Viagra

Pfizer knew that this serendipitous discovery could well become a blockbuster, promptly diverting more resources into the development of the drug. By the end of summer that year, research on the compound completely shifted from chest pain to impotence studies, featuring the compound and a device called a Rigiscan (no explanation needed).

Sildenafil citrate – trade name Viagra – was approved on 27 March 1998 and hasn’t looked back – generating annual revenue close to US$2 billion at its peak – with big names such as football star Pelé endorsing the use of the drug. It was a classic example of drug repositioning: the development of new uses for existing drugs.



Viagra’s Supply Issues

Demand was massive right from the start, with Pfizer struggling to keep up supply; hundreds of thousands of prescriptions were filled every week. It took six long months before Viagra was officially approved for use in Europe; outside the U.S., people wanting in on the pill had to look to alternative sources.

Because Viagra was prescription-only, those who wanted it had to visit a urologist, which also meant long, awkward waits at clinics avoiding eye contact with other men in the same… situation. Back then, the topic of erectile dysfunction – a term coined by Pfizer – carried enough social stigma that men in oversized trench coats and sunglasses at the doctor’s office became a common occurence.

All of these factors quickly led to Viagra being exploited outside the usual channels. In some countries, Viagra on the black market could fetch up to five times the price of its prescription (~US$10 in 1998).

counterfeit viagra large bag police seized
Viagra: also the face of the counterfeit drug industry.

As the number of people with internet access increased, so too did illegal online sales of Viagra. Online pharmacies became rampant, with their discreet nature appealing to consumers preferring not to visit a clinic for their needs. However, this also meant that sellers could market their products without revealing their identities, resulting in shady practices with regard to prescription medicines.

Counterfeit Viagra quickly flooded the online market, with illegal manufacturers realizing that they could now sell this blockbuster drug without having to worry about the strict regulatory requirements on safety and efficacy. And this doesn’t appear to be slowing down, with Pfizer’s Global Security reporting in 2013 that close to 80% of the Viagra on the market were fakes.

Bleak Future for the Blue Pill

With precious market exclusivity ticking ever closer to expiry, Pfizer has wasted no time planning for the inevitable flood of generics entering the US market. In fact, the patent detailing the synthesis of sildenafil citrate expired on 27 September 2012, allowing others with the capacity to manufacture it to do so2. And indeed others have; generic forms of the drug are available for sale at a fraction of the original’s cost, but only outside of the U.S. where Viagra isn’t protected by market exclusivity.

Within the U.S.? A quick search on the FDA website of ‘sildenafil citrate’ turns up results that show six other pharmaceutical companies that recently have had their therapeutic equivalents approved, waiting to sell the moment the clock ticks midnight on 22 April 2020. Indeed, Pfizer has agreed to terms with one of these – Israeli pharmaceutical giant Teva – allowing them to release generic versions of sildenafil in the U.S. early (Dec 2017). At the time of writing, Teva has already released their generic versions onto the market.

viagrasales
December 11, 2017 – the beginning of the end for Pfizer’s Viagra.

In order to combat the appeal of online pharmacies, Pfizer has also launched its own online platform for Viagra, where consumers can be prescribed and sold the medication simply by filling up a questionnaire. Pfizer has also cut the price of Viagra to US$34 per pill at the time of writing, almost half the going price a year before.

Furthermore, in a desperate bid to hold on to market share against the oncoming tide of generic sildenafil, Pfizer has also launched its own generic for those who might have their heads turned. Perhaps learning from Lipitor – its other blockbuster, and the best-selling drug of all time – Pfizer doesn’t want to wait for exclusivity to expire before taking aciton. But its generic version? Manufactured as a white pill, perhaps signaling the end of an era. But boy, what a run the little blue pill has had.



Reference

  1. Boolell, M., Allen, M. J., Ballard, S. A., Gepi-Attee, S., Muirhead, G. J., Naylor, A. M., … & Gingell, C. (1996). Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction. International journal of impotence research, 8(2), 47-52.
  2. Bell, A. S., Brown, D., & Terrett, N. K. (1993). U.S. Patent No. US5250534A. Washington, DC: U.S. Patent and Trademark Office.
  3. Internet Drug Outlet Identification Program Progress Report for State and Federal Regulators: July 2013 (Rep.). (n.d.). National Association of Boards of Pharmacy.

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