doping

Use of drugs for erectile dysfunction in sports

By Dr. Nicola Sacchi - Author of the book: Drugs and doping in sport -

Introduction

Among the latest discoveries in the pharmaceutical field, a prominent role is played by the phosphodiesterase type 5 inhibitors (5PDE) used for the treatment of erectile dysfunction.

These substances have been enormously successful on the market, so much so that in the last ten years they have filled the coffers of manufacturing industries. Pfaizer, the first to introduce a drug of this type, Viagra, has become the most important pharmaceutical company in the world thanks to the sales of this drug.

Mechanism of action of phosphodiesterase type 5 inhibitors

The phenomenon of erection is due to a relaxation of the smooth muscles of the cavernous bodies of the penis, followed by arterial vasodilation. The parallel constriction of the venous vessels causes stagnation of blood which is followed by an erection.

The relaxation of the smooth muscles of the corpora cavernosa is a phenomenon mediated by nitric oxide (NO). It activates the enzyme guanylate cyclase which catalyzes the transformation of guanosine triphosphate (GTP) into cyclic guanosine monophosphate (cGMP) which stimulates muscle relaxation. The cGMP is degraded by a phosphodiesterase of which at least six isoenzymes are known. In the corpus cavernosum the phosphodiesterase involved is type 5 phosphodiesterase (5PDE).

The drugs for erectile dysfunction work by inhibiting 5PDE, which causes an increase in the blood supply due to the increased concentration of cGMP, followed by an improvement in the erection. At therapeutic dosages these substances do not produce erection in the absence of sexual stimulation.

Side effects

There are obviously different possible side effects caused by the intake of these substances. The main risk is related to the fact that vasodilation can lead to hypotension, with possible cardiovascular imbalances. Treatment of erectile dysfunction has therefore been associated with serious cardiovascular events such as myocardial infarction, intermediate angina pectoris, sudden cardiac death, ventricular arrhythmias, stroke, transient ischemic attack and blood pressure changes.

Furthermore, sildenafil seems to inhibit beta adrenergic cardiac stimulation; in fact, while the effects of sildenafil at cardiac level were minimal in rest conditions, in conditions of beta stimulation or pressure overload sildenafil decreased the cardiac responses induced by dobutamine and the systolic effects resulting from beta stimulation. It should be added that these effects are certainly aggravated by a suboptimal cardiovascular condition.

Among the side effects it should also be remembered that there may also be disorders such as vomiting, diarrhea, dyspepsia, hot flushes, in addition to the already mentioned changes in blood pressure.

Active principles and trade names

Among the cited molecules, the progenitor and the first to be marketed was sildenafil (Viagra); after its release on the market, two other drugs of the same class were born, namely tadalafil (Cialis) and vardenafil (Levitra). Of the three compounds Viagra is the one with the shortest duration of action (6/8 hours) but stronger, while the others have a much more prolonged activity (Cialis over 24 hours) but less intense. Recently, avanafil (Stendra) has also been introduced to the market, which is distinguished from other PDE5 inhibitors by a rapid onset of action, about 15 minutes, but also for a shorter duration of action

Use in pulmonary hypertension and in sport

Phosphodiesterase type 5 inhibitors have recently been shown to be effective also in the treatment of another pathology of vascular origin: pulmonary hypertension. This pathology is caused by a strong constriction of the blood vessels of the lungs, which reduces the ability of the respiratory system to bring oxygen to the body. Due to the vasodilatory action, sildenafil and other substances of this class dilate the artery and other pulmonary vessels, causing lowering of arterial pressure in the lungs and increasing the availability of oxygen . All this makes the molecule in question also able to bring considerable advantages in terms of energy yield under stress: the possible benefits for the user translate into an improvement in the ability to do aerobic exercise .

Particular studies conducted at high altitude have also shown how sildenafil leads to a significant increase in oxygen saturation in the blood during physical activity. In addition, an increase in maximum workload and maximum cardiac capacity was highlighted. In practice, sildenafil has been shown to significantly improve physical abilities under hypoxic conditions due to altitude.

In light of these findings, some sportsmen use sildenafil with the aim of improving aerobic performance in long-term sports.

There is still little information on the ability of these substances to positively influence physical performance; however, although not all studies are able to demonstrate real benefits for athletes in endurance skills, the practice of using 5PDE inhibitors before performing in endurance sports is increasingly common. The vasodilatory capacities of these substances, particularly in the lung, can improve the ability to oxygenate the muscles; for this reason more and more endurance sports athletes are using these products.

To confirm this practice among athletes there is also an Italian study published in 2014 [Loraschi et al.], Which examines this practice among cyclists. This study, through an anonymous questionnaire, announced the fact that in a sample of cyclists, several of them admitted to using Sildenafil before a competition.

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