Shahar Madjar, MD, Journal columnist

Sildenafil is the generic name of Viagra. Its discovery as a treatment for erectile dysfunction came about serendipitously. Serendipity is a fancy word for “by a happy accident,” or “by a lucky chance.”

You are looking for an answer to one question, and you stumble upon a better answer to a question you have never entertained. For scientists and doctors, the word serendipity is loaded with meaning. We just know that not all discoveries are purposeful, some just happen. Therefore, the word serendipity rolls on my tongue like the best of wines.

In the case of Sildenafil, it happened like that: Pfizer, a giant pharmaceutical company with its headquarters in New York, was working on a compound called UK-92,480. The drug was shown earlier to produce widening of the coronary arteries (the blood vessels supplying the heart) in dogs, rabbits, and hypertensive rats.

Pfizer’s scientists examined the effects of the compound in the treatment of angina–chest pain caused by narrowing of the coronary arteries. Clinical trials in humans started in 1991-1992.

Several of the participants in these earlier studies reported a curious side effect–spontaneous penile erections! Did I mention serendipity?

UK-92,480 was later named Sildenafil (generic name). Its brand name is Viagra. It was nicknamed the “Little Blue Pill.”

How does Viagra work? The short answer is: by increasing the blood flow into the penile erectile tissue. The long answer is a bit complex and it is beyond the scope of this article (if you are curious, write to me, and I will send you a full explanation).

The FDA approved Viagra in March 1998. A testament to its efficacy, and its popularity, is in its market success. According to Fortune magazine, Viagra brought in $1.6 billion in 2016 global sales.

The clinical trials tell the same story from a different, scientific perspective. In a 1996 clinical trial on 329 patients with a diagnosis of erectile dysfunction lasting six months or more, 69% of attempts of sexual intercourse were successful compared with only 22% in patients who took a placebo.

The side effects of Viagra are mostly tolerable and reversible. The most common side effects are headache and flushing of the face. Less common side effects include nasal congestion, back pain, muscle ache, dyspepsia, blurry vision, and a change in the perception of color–taking it, you may start seeing a blue, or a purple hue. Other, extremely rare side effects include priapism (prolonged erections), loss of vision, and loss of hearing.

Do not take Viagra if you are on nitrates, such as nitroglycerin. Nitrates are typically used to prevent chest pain (angina), or to treat the symptoms of heart failure. Viagra strengthens the effect of nitrates and taken together, a severe drop in blood pressure, even death, may occur. There are other contraindications. Therefore, before taking Viagra, you should consult your health care provider.

Here is what I tell patients: Viagra doesn’t initiate erections. It just makes erections stronger. To achieve an erection on Viagra, you have to be physically stimulated. For best results, take Viagra about an hour prior to sexual intercourse. Take it on an empty stomach, or after a light meal.

It is okay to drink a small amount of alcohol on the nights you are planning to use Viagra. Start with a low dose (25 mg), and, if your response is insufficient, try a higher dose on a different day (50, then 75, then 100 mg). Do not take more than one dose daily and don’t exceed 100 mg a day. And, to eliminate stress and frustration, consider experimenting with the medication on your own before trying it with your sexual partner.

If you fail a trial of Viagra, you can try other medications of the same group. Vardenafil (Levitra) is as effective as Viagra. Its main advantage is that is doesn’t alter color perception–you won’t see blue, nor purple. Tadalafil (Cialis) also has a success rate similar to that of Viagra, but it has longer duration of action (24-36 hours compared with 6-8 hours with Viagra). Tadalafil can be taken daily, thus eliminating the need for planning prior to sexual intercourse.

Viagra was discovered serendipitously. It joins many other “happy accidents” that have turned into great scientific discoveries. Other serendipitous discoveries include Alexander Fleming’s discovery of penicillin, and Wilhelm Roentgen’s discovery of X-ray. These discoveries weren’t totally “out of the blue” happenstances of pure chance. In all of these events, a question had to be asked; an honest attempt at answering that question had to be made; an unexpected pattern had to be recognized. Louis Pasteur words sum it all up: “Chance favors the prepared mind.”

Editor’s note: Dr. Shahar Madjar is a urologist at Aspirus and the author of “Is Life Too Long? Essays about Life, Death and Other Trivial Matters.” Contact him at smadjar@yahoo.com.