For those who have read my endless series of blogs on cardiovascular disease, you may know exactly where I am going at this point.
Some time ago, Pfizer were developing a drug to treat angina. It blocked an enzyme called phosphodiesterase type-5. [Although I believe that its exact mechanism of action was not known at first]. To put it another way, this drug was a phosphodiesterase type-5 inhibitor (PDE5i).
The moment Pfizer found out what enzyme this drug blocked, they tried to patent the pathway that blocked this enzyme. Pharmaceutical companies trying to patent biological pathways. Perhaps I should try to patent the Krebs cycle, and charge everyone on the planet for having such a thing. Kerchingggg!
‘The U.S. patent office appears to have granted Pfizer a patent covering any drug that blocks this enzyme, meaning that it can sue all of its potential competitors.’1
Luckily, this time they were rebuffed.
Anyhoo, back to the drug. During phase one clinical trials, where humans are given the drug for the first time to see what effects it may have, many of the volunteers were hanging on to their medication, rather than handing them back. This was very unusual. Almost unknown in fact.
When researchers went out to find out why this was happening it was discovered, not quite sure who admitted to this, that sildenafil/Viagra improved erectile function. Thus, Viagra, the first PDE5i, was born. The first drug that worked simply and effectively to improve erectile dysfunction (ED). As for treating angina… that piffling indication was rapidly shelved as the dollar signs appeared in the sky above Pfizer HQ. Sex, as they say, sells.
In truth, it is actually one of the best drugs ever. Not only does is treat ED, but it can also be used by mountaineers to prevent pulmonary oedema (fluid filling up in the lungs), which is one of the major symptoms of altitude sickness. It does this by reducing the blood pressure in the pulmonary vessels (blood vessels in the lungs).
To explain a little further. If you climb very high, and the oxygen level drops, the heart pumps blood harder and harder through the lungs to get as much oxygen as possible into the system. This can result in fluid leaking out of the vessels and into the lung tissue, so they fill up with fluid. At which point you effectively drown, so you die. Viagra stops this happening, by lowering the blood pressure in the lungs.
Unsurprisingly, Viagra is used to treat people who have pulmonary hypertension (high blood pressure in the blood vessels in the lungs) at sea level. It is sold under the name Ravatio, for this indication – but we know that it is just Viagra. In addition, Viagra can be used to treat Raynaud’s disease, where the small blood vessels supplying the fingers and toes constrict, leading to painful cold fingers.
So, here we have a drug that can treat angina, pulmonary hypertension, erectile dysfunction and Raynaud’s disease at the same time. Thus, you can have great sex at twenty thousand feet above sea level, not get chest pain, or breathless, and stay warm at the same time. What more could a man ask for?
How does it do all these things? The answer is that it increases Nitric Oxide (NO) synthesis in endothelial cells. When it does this in the penis, it stimulates erections. In the heart, it opens up coronary arteries. In the lungs, it dilates the blood vessels, in fingers and toes it opens up arteries. So, all of the many different effects, are all due to exactly the same process – increased NO synthesis. Viagra also lowers blood pressure – as you would expect.
At the risk of blowing my own trumpet, I talked about this in my book ‘Doctoring Data,’ under the heading ‘Viagra and the drugs of unintended consequences.’ I posed the question. ‘If we were to prescribe Viagra as an antihypertensive, which is entirely possible, and it were found to reduce the risk of heart disease and stroke, which effect do you think would be responsible for the benefit? The blood pressure lowering effect, or the anticoagulant effects? Or something else.’
Since I wrote those words, someone has actually looked at the impact of PDE5is on cardiovascular disease. Researchers at Manchester University, in the UK, studied the use of Viagra in people with diabetes – who often have erectile dysfunction. Here is what they found:
‘Viagra could prevent heart attacks, according to research. Patients taking the male impotence drug were found to have a lower risk of having a heart attack or dying from heart failure than those not on the medication. The lead scientist told the Daily Express the findings are “incredibly exciting”.2
The research paper was published in ‘Heart’, a BMJ journal. Actually, this paper was published last year, but only seems to have hit the press in the last few days. I spotted it in the Times a few days ago.
Here are the main results (for those readers who like their statistics)
‘Results: Compared with non-users, men who are prescribed PDE5is (Viagra, Cialis and the like – my words) (n=1359) experienced lower percentage of deaths during follow-up (19.1% vs 23.8%) and lower risk of all-cause mortality (unadjusted HR=0.69 (95% CI: 0.64 to 0.79); p<0.001)). The reduction in risk of mortality (HR=0.54 (0.36 to 0.80); p=0.002) remained after adjusting for age, estimated glomerular filtration rate, smoking status, prior cerebrovascular accident (CVA) hypertension, prior myocardial infarction (MI), systolic blood pressure, use of statin, metformin, aspirin and β-blocker medication. PDE5i users had lower rates of incident MI (incidence rate ratio (0.62 (0.49 to 0.80), p<0.0001) with lower mortality (25.7% vs 40.1% deaths; age-adjusted HR=0.60 (0.54 to 0.69); p=0.001) compared with non-users within this subgroup.’3
For those who don’t like their statistics quite as much as me (shame on you). I shall attempt to simplify.
- Over a seven year period, those men taking PDE5is (Viagra Cialis and the like) had a 4.7% reduction in overall mortality – compared to men who did not.
- Those taking Viagra were 38% less likely to have a myocardial infarction
- If you did have a myocardial infarction, those who were taking PDE5is had a 25.7% death rate. Those who were not taking PDE5is had a 40.1% death rate. So, if you were unfortunate to have a heart attack, you were 14.6% less likely (absolute risk reduction) to die if you were taking PDE5is.
Or, to shorten this even more
- 4.7% reduction in overall mortality
- 38% reduction in MI (relative risk reduction)
- 14.6% reduction in death after an MI
Whilst the first figure of a 4.7% reduction in overall mortality may not sound terrible exciting, it knocks all antihypertensives and cholesterol lowering medication into a cocked hat. Even if you add them together and multiply by two – on their best day. Because 4.7% is an absolute risk reduction. [Absolute mortality reduction in the Heart Protection Study (HPS), the most positive statin trial, was 1.8% over five years]
The benefits of Viagra are even more startling when it comes to having a heart attack (MI). The current ‘gold standard’ treatment of choice is Primary Percutaneous Coronary Intervention (PCI), which basically means popping a stent into a blocked coronary artery to open it up again.
It has been estimated that PCI results in a 2% absolute reduction in mortality4. On the other hand, Viagra gives you, very nearly, a 15% reduction in overall mortality. Or, to put it another way, Viagra may be seven and a half times as effective as PCI.
But it does not end here. it was also found that men with heart failure were 36% less likely to die if they took a PDE5i.
‘In the other subgroups, there was an inverse association between PDE5i use and all-cause mortality. Those with a recorded history of congestive cardiac failure, TIA and PVD had 36%, 40% and 34% lower risk, respectively.’ [A TIA is a transient Ischaemic attack/small stroke. PVD is peripheral vessel disease.]
Congestive cardiac failure is usually shortened to heart failure. [This 36% is a relative risk reduction, and I could not work out what the absolute risk was from the paper. I am probably too thick].
The effect on heart failure is almost certainly because another benefit of increasing NO is that you increase ‘angiogenesis’, otherwise known as, ‘the creation of new blood vessels’. If a coronary artery does completely block, this often leads to heart failure, as not enough oxygen and other nutrients can get into the heart muscle downstream.
However, if collateral blood vessels develop, the blood will be directed around the blockage and back into the artery downstream, through these newly created blood vessels. Although collateral circulation is not as effective as a fully patent coronary artery, it will create a significant flow of oxygen and nutrients once more. Thus, heart failure will be greatly improved.
Louis Ignarro, who identified nitric oxide (NO) as the key chemical messenger that dilated blood vessels, and won the Nobel Prize for doing so, decided to start treating people who have end stage heart failure with l-arginine. He had been looking for a substance that would, naturally increase NO, and found l-arginine did the job best. He has had some amazing results. Perhaps he should start using Viagra instead.
This study, I must add, was not interventional, it was observational. However, it strongly supports the hypothesis that increasing NO synthesis is just about the most important thing you can do. If you want to avoid dying from CVD.
Do I think everyone should take Viagra? Well, if you have heart failure, diabetes and a high risk of CVD – probably. Will you get a doctor to prescribe it for you, for CVD prevention? Absolutely no chance. Will anyone ever fund a study on this? With the drugs now off patent – no chance.
Oh, the joys of modern medicine. Unless someone does a controlled randomised double blind study on a medication, doctors will not prescribe – are not allowed to prescribe. However, virtually the only people with the money to do such studies are pharmaceutical companies. If the patent life of a drug has expired, no money can be made. So, no trial will be done. So, drugs that are almost certainly beneficial wither on the vine.
Unusually, for me, I do not blame the pharmaceutical companies for this. They are not charities. They need to make money or they die. You cannot expect them to spend hundreds of millions on a clinical study, without any possible means of gaining a return on their investment. We live in a funny old world.
In the meantime, look to other things that can increase NO synthesis. L-arginine/L-citrulline does this. Potassium does this. Sunlight does this. Exercise does this. Meditation does this. Vitamin D does this, as does Vitamin C. What are you waiting for? Go for a walk in the sun and eat an orange – you will live forever.