HEALTH

Viagra benefits go beyond the bedroom

An important action of erectile dysfunction drugs is their effect on the dilatation of blood vessels

WHILE most of us are familiar with the kind of high blood pressure (hypertension) that imposes stress on the left heart chambers, there is another kind of hypertension which involves only the right heart chambers. This is termed pulmonary arterial hypertension or PAH.

Secondary PAH is usually seen in those with severe lung disease (often related to smoking), but sometimes, the condition can exist without any underlying cause, and this is known as primary PAH.

The affliction, especially primary PAH, is a life -threatening condition which is characterised by a progressive increase in the blood pressure in the lung vessels leading to right heart failure.

Smokers

Long term smokers with chronic lung disease develop constriction of the vessels in their lungs, thereby increasing the resistance to the flow of blood being pumped from the right side of the heart into the lung vessels, where oxygen is to be absorbed and carbon dioxide removed.

This increased resistance to the flow raises the blood pressure in the right heart chambers, resulting in right-heart high blood pressure or PAH.

Erectile dysfunction drugs for the heart

You may be surprised that PAH can be managed with drugs primarily used for men with erectile dysfunction (ED), the condition under which a man is unable to maintain an adequate erection for sexual intercourse.

Currently, the ED drugs available include sildenafil citrate (also known as Viagra), tadalafil (Cialis) and vardenafil (Levitra). An important action of these drugs is their effect on the dilatation of blood vessels. The process of blood vessel dilatation requires the release of the chemical nitric oxide (NO) by the cells lining the vessels. This triggers a reaction which results in the production of cyclic guanosine monophosphate (cGMP), the main chemical that effects the vessel dilatation necessary in penile erection.

The ED drugs act by inhibiting the enzyme PDE5, which breaks down cGMP. With the action of the PDE5 enzyme blocked, the cGMP accumulates, resulting in relaxation of the muscle in the vessel wall causing dilatation of the artery and increasing the size of the vessels.

In patients with PAH, the net effect is lowering resistance to blood flow, and thereby lowering right heart pressure. These PDE5 inhibitor drugs are safe for healthy hearts, but should be used with precautions in men with pre-existing heart disease. Currently, sildenafil and tadalafil are FDA-approved for the treatment of PAH.

Since PDE5 is found mainly in the walls of the arteries in the lungs and penis, the effect of ED drugs is primarily in these two areas. Studies have shown that the use of ED drugs in those with PAH is associated with an improvement in exercise tolerance and a reduction of pressure in the right heart chambers. Some studies have also suggested that these drugs may also have a beneficial effect of reducing the likelihood of the progression of PAH.

Beyond the heart

Interestingly, ED drugs have also been found to be beneficial in other conditions. So, the next time you are intending to go up a high mountain or have a holiday in a mountainous resort, you may consider taking Viagra.

Going up to high altitudes can sometimes cause illness in people with existing heart and lung problems. The low oxygen environment at higher altitudes can cause the blood vessels in the lung to constrict, thereby increasing pressure in the lung vessels.

The increased pressure within the lung vessels may cause the vessels to leak fluid and hence interfere with the exchange of oxygen in the lungs. This condition is called high-altitude pulmonary oedema (HAPE) and it can occur shortly after ascent to high altitudes in susceptible individuals. This dreaded condition has a mortality of more than 40 per cent, accounting for most high-altitude deaths.

Studies published by Richalet in 2004 (American Journal of Respiratory and Critical Care Medicine) and Fagenholz in 2007 (High Altitude Medicine and Biology journal) have shown that ED drugs, in particular Viagra, protect against the development of HAPE and were beneficial for the treatment of HAPE.

The Centers for Disease Control and Prevention (CDC) in the United States, in addition to strongly recommending acetazolamide prophylaxis in all individuals who are susceptible for HAPE, also includes the use of ED drugs such as tadalafil or sildenafil (Viagra) for HAPE prophylaxis.

Exercise caution

Before smokers with damaged lungs and exertional breathlessness think that ED drugs are a panacea for their condition, they should be aware that ED drugs are not without their side effects.

Nitric oxide, the chemical involved in vessel dilatation, is generated by all the arteries in the body and hence the use of the PDE5 inhibitor drugs can cause a widespread vessel dilatation causing a temporary blood pressure drop by 5 to 8 mmHg.

The effect of vessel dilatation can cause side effects such as headaches, flushing and nasal congestion. Users of Viagra may complain of a tinge of blue in their vision. Rare but serious adverse effects include visual impairment and sudden hearing loss.

Although Viagra consumption was reported by McGwin in 2006 to be associated with a rare visual impairment termed non-arteritic anterior ischemic optic neuropathy, this was not reported when used in other PAH studies. Nevertheless, should you have impaired vision, buzzing sound in your ear or decreased hearing after taking Viagra, you should seek medical attention immediately.

Contraindications

As Viagra is a vessel relaxant, great care must be exercised when given to those with low blood pressure (BP) as it may drop the BP further. Viagra should not be taken if you are also taking medications that contain medications such as nitrates, nitric oxide donors or alpha blockers.

Nitrates, which are drugs that are frequently given to those with heart disease, widen arteries by increasing their supply of nitric oxide. By this action, they can increase the blood flow to blocked arteries in the heart. These drugs when taken with Viagra can cause a significant drop in blood pressure as they both increase nitric acid production.

Healthy volunteers who were given Viagra followed an hour later by nitroglycerin (a type of nitrate) experience blood pressures drop by 25 to 51 mm Hg. This severe drop in blood pressure may not only cause a loss of consciousness, but can also be life threatening.

Finally, while ED drugs present smokers an opportunity to alleviate symptoms and improve the quality of life, not all smokers with bad lungs may find relief with Viagra.

BT is now on Telegram!

For daily updates on weekdays and specially selected content for the weekend. Subscribe to t.me/BizTimes