Viagra, or sildenafil, is the world’s best-known and most-discussed erectile dysfunction (ED) drug. Introduced to the U.S. market in 1998, the pill is actually a treatment for pulmonary arterial hypertension (PAH), approved by the FDA in 2012 for use in men with that condition. But what is really behind the meteoric rise of this drug? We take a look at five things you might not know about Viagra.
1. It Started as a Treatment for Pulmonary Arterial Hypertension
In 1992, after discovering a correlation between sildenafil (Viagra’s active ingredient) and pulmonary arterial hypertension (PAH), Dr. Rogerio Afonso of the Universidade de Sao Paulo in Brazil performed a series of animal testing to further investigate the link. His studies revealed that sildenafil significantly increased the diameter of the blood vessels in the lungs – demonstrating that it could potentially treat PAH – and that it was well-tolerated by the animals. In 1995, Dr. Afonso and his team conducted a double-blind, placebo-controlled clinical trial with 30 patients with PAH. The trial compared sildenafil (100 mg) to a placebo (pill-sized particle, matching the texture of the real drug) and found that the patients who received the drug had a significant increase in their blood flow to their lungs.
In 1998, Dr. Afonso and his team published their findings in The New England Journal of Medicine. Two years later, in October 2000, the FDA approved sildenafil for the treatment of PAH and in 2004, the United Kingdom’s National Institute for Health Research (NIHR) followed suit with a similar approval. Now, in 2020, sildenafil is the most prescribed drug for erectile dysfunction and PAH across the world. In 2019, the pharmaceutical company that makes sildenafil announced that it had sold more than 500 million pills since its FDA approval.
In addition to demonstrating that sildenafil can help patients with PAH, Dr. Afonso’s studies also revealed a correlation between the dosage of the drug and the improvement of the patients’ conditions. Specifically, patients who took 100 mg of sildenafil every other day reported the greatest improvement in their pulmonary function. This improvement was also demonstrated by elevated mean arterial blood pressure and the increased blood flow to the lungs. Because of this, some experts recommend that patients with PAH continue taking 100 mg of sildenafil every other day even after their condition stabilizes.
2. Viagra Has Been Around for Long Enough to Be Confirmed as Effective
In the 1970s, a group of researchers at Pfizer found that sildenafil helped prevent or alleviate the symptoms of altitude sickness in rats. In 1992, after discovering the drug’s potential to treat PAH, Dr. Afonso’s team carried out a study to investigate the drug’s effect on rats that were already experiencing the symptoms of altitude sickness. The team found that sildenafil significantly improved the rats’ condition, suggesting that it can help humans, too.
While rats are not humans and their conditions are not necessarily indicative of human responses, the findings in Dr. Afonso’s study are sufficient to support sildenafil’s effectiveness for treating altitude sickness in humans. In fact, in 2020, the FDA approved the use of sildenafil for that condition – again, in addition to the use of the drug in PAH).
3. Viagra Is Generally Safe
According to the FDA, as of April 2020, there have been no reported deaths related to the use of Viagra. The agency also lists the drug as “generally safe.” This is good news for patients who are concerned about the safety of their medication and for physicians who prescribe it, especially compared to prescriptions for other medications. While it is always important to talk to your doctor about possible side effects and drug-drug interactions, generally speaking, Viagra is a relatively safe option for patients with erectile dysfunction and PAH.
For those who are sensitive to aspirin, it is important to note that some studies suggest that sildenafil may interfere with the blood-clotting process. However, because of the vitamin C–like effects of sildenafil, some experts recommend that patients taking the drug for PAH discontinue their aspirin therapy altogether.
4. It Has Been Used in Humans for Decades
Although sildenafil was first discovered and developed for medical purposes, it has been used in humans for non-medical purposes for more than 30 years. In 1939, the drug was found to improve the vision of patients suffering from vernal (spring) conjunctivitis, a condition that can be caused by exposure to dry, cold air or wind. In addition to improving vision, sildenafil has also been shown to treat pulmonary hypertension, prevent cardiovascular disease, and inhibit the growth of tumor cells.
In the 1970s, sildenafil was also found to significantly reduce the mortality of patients with AIDS, particularly in combination with other medications. And in the 20th century, the drug was used to prevent or alleviate the symptoms of altitude sickness in humans, as discussed above. (This is also why many travelers to high altitudes experience headaches, fatigue, and shortness of breath – the same symptoms that can occur with PAH.)
Because sildenafil has been shown to be safe and effective for so many different conditions in humans, it has literally been adopted by many as a panacea or ‘one-stop-shop’ for various ailments. In 2019, some doctors prescribed the drug in combination with some of the most popular erectile dysfunction medications in an effort to help patients experience improved sexual function. While some of the side effects of combination therapy include acid reflux, diarrhea, flushing, and a general feeling of being unwell, the relief of patients’ conditions – and the popularity of the medication – speak for themselves.
Additionally, some experts have suggested that the drug may also be able to help protect patients against the negative effects of radiation exposure. Because of this, sildenafil has been referred to as a ‘compound radioprotector’ and could, therefore, be used in the radiation treatment of cancer.
5. It Hasbeen Tested In Varying Conditions
There are five different clinical trials that Dr. Afonso’s team conducted to investigate the effectiveness of sildenafil in the treatment of PAH. These trials were listed in the 1998 New England Journal of Medicine study and were conducted at multiple medical centers around Brazil. In total, the trials included over 300 patients and three-to-four months of follow-up. The trials compared sildenafil to a placebo in a double-blind fashion and confirmed its efficacy in improving the patients’ condition. Additionally, the trials also assessed the safety of the drug.
One of the trials involved 30 patients with PAH who were either newly-diagnosed or were already receiving treatment. In this trial, the patients received either a placebo or 100 mg of sildenafil every other day. At the end of the three-month trial, patients who took sildenafil experienced a significant improvement in exercise tolerance and in their ability to participate in social activities. Another trial, for 40 patients with PAH, compared the effect of 100 mg of sildenafil versus 200 mg of the drug every other day. Again, the patients who received the drug had improved exercise tolerance and socialization skills compared to the placebo group. (For comparison, patients with pulmonary hypertension usually take either a beta-blocker or a calcium-channel blocker as part of their treatment. Beta-blockers, such as propranolol (Inderal), are used to regulate the blood pressure of patients with heart disease; calcium-channel blockers (CCBs), such as nifedipine (Adalat) or amlodipine (Norvasc), are prescribed to patients with high blood pressure. Both classes of medications have been shown to improve PAH patients’ conditions.)