By Dr. Colin Michie FRCPCH
Viagra (or sildenafil) has just had its 20th birthday. The little blue pill holds many records, including one of the fastest growing prescription uptakes ever for a medication. Its effectiveness has brought the common physical challenges of erection from humiliating awkwardness into public discourse. Approximately half of men ages 40-70 suffer with erectile dysfunction; this proportion is growing as populations age, and numbers of those suffering with diabetes and cardiovascular diseases increase.
Sildenafil works by inhibiting an enzyme – phosphodiesterase 5. This has the effect of relaxing smooth muscles around arteries, increasing the blood flow through them. The drug was initially planned as a treatment for angina, but researchers, rapidly followed by the public, were impressed by its actions in the penis. Sildenafil causes a considerable increase of blood flow there, increasing pressures in the corpora cavernosa if a man is sexually stimulated, either psychologically or physically. When the two cylinders of the corpora cavernosa are filled, the penis becomes erect and firm. This process is usually controlled by brain and spinal nerves, together with hormones such as testosterone.
The male focus on sexual potency once drove a diverse economy of advertising, snake oil medicines and a great variety of curious contraptions. Almost none of these had any value. Reframing concerns about impotence, with their enormous emotional and historical baggage, to the physical problems of erectile dysfunction that respond to sildenafil and similar compounds, has had positive effects on male mental health. These medications do not increase libido or satisfaction, but ensure safe, enhanced and prolonged erectile function. Men on treatment are recorded to have improved self-esteem, with less anxiety, depression or social isolation.
Sildenafil as an oral treatment delivers physical effects after 30 to 60 minutes; half of the drug is metabolised within four hours in most men. Side effects of taking sildenafil, if they occur, are usually mild and resolve by themselves rapidly. These include facial flushing, headache, nasal congestion and indigestion. If those without erectile problems use sildenafil, it may prolong erections. Side effects or queries relating to possible drug interactions should be reviewed with a medical consultation. Sildenafil does not have obvious pharmacological effects on women with respect to sexual functions.
Sildenafil helps everyone with other circulatory problems, including the pulmonary arteries that take blood from the heart into the lungs. Two groups of patients need help with this: First, adults with heart failure or lung cancer and, second, premature infants requiring ventilation. At both ends of the age spectrum, sildenafil increases blood flow into their lungs, improving oxygen collection and reducing the workload on the heart. This invaluable treatment saves lives.
An enlarged prostate gland causes older men trouble. Symptoms include a sensation of urgency to pass urine, reduced urine flow, frequent urination and a need to get up and pass urine at night. Sildenafil relaxes smooth muscles around the neck of the bladder and perhaps within the prostate too, bringing significant relief. These symptoms are common in men who also suffer with erectile dysfunction – it is possible that the problems are linked, although the biology of this is unclear.
Shortage of blood flow (and therefore oxygen supply) in the brain causes numerous human disorders, shortens life, and can have profound effects on loved ones and families. Damage to the networks of small vessels in our brain is thought to cause approximately 40% of dementias, about a third of strokes, and most brain haemorrhages. A proportion of infants suffers brain insults from a shortage of oxygen around the time of birth – birth asphyxia.
In animal models of all these situations, sildenafil improves neurological outcomes by reducing inflammation in injured brains and helping nerve cells to adapt. Trials of sildenafil in adults for these harms have not been reported as yet, although work in new-borns is particularly encouraging. Large numbers of US men have been treated with sildenafil or similar medications over the last decades. These patients have reduced overall mortality and death from dementia or cardiovascular diseases and their cognitive health has improved. Perhaps this area will become a further application for sildenafil in future.
Sildenafil’s efficacy means it is often sold to us unknowingly. For instance, dietary supplements have shown spectacular market growth – sales of herbal aphrodisiacs are always popular! Laboratory testing consistently finds some of these are adulterated with sildenafil or other inhibitors of phosphodiesterase 5, even though they cannot enhance libido. Not all herbal treatments are quite what they seem!
Improving blood flow within our bodies is a valuable strategy for improving our health. Viagra, invented by pharmacists, has demonstrated just how many barriers may be overcome using this type of therapy. Sildenafil has powerful effects and improves the quality of life for many.
Dr. Colin Michie specializes in paediatrics, nutrition, and immunology. Michie has worked in the UK, southern Africa and Gaza as a paediatrician and educator and was the associate Academic Dean for the American University of the Caribbean Medical School in Sint Maarten a few years ago.
