Sildenafil (Viagra) for treating Erectile Dysfuntion

Erectile dysfunction (ED) is a common but under-reported complaint. It is expected that the number of requests for help due to erectile dysfunction will increase with the advent of sildenafil (Viagra), the first effective oral erection stimulant.

Sildenafil

Sildenafil is an inhibitor of the enzyme phosphodiesterase type 5. It causes erection of the penis, by maintaining the relaxation of the smooth muscle tissue of the swelling body.

The first clinical results show that treatment with sildenafil is safe and effective, if prescribed by a sexually qualified physician.Erectile dysfunction is and remains a symptom that primarily requires causal treatment.

Erectile Dysfunction, is defined  as a permanent or recurrent inability to obtain or maintain an adequate erection. until the completion of sexual activity. However, not every failure of the erection should be considered as a disorder. One speaks of this only when the deviation makes it impossible for the man to take part in the sexual intercourse as he would like and if the deviation causes obvious suffering or relationship problems.

Erectile dysfunction is a common complaint, especially in older men. Obviously not everyone will experience erectile dysfunction as a problem. Moreover, it is striking that not erectile dysfunction but ejaculatory dysfunction is the most frequently experienced sexual problem and that erectile dysfunction does not increase as an experienced problem with increasing age.

How does an erection happen ?

An erectile dysfunction can generally be based on 3 mechanisms: (a) disturbance of the stimulus transfer in or from the central nervous system (neurogenic / psychogenic disorder); (b) insufficient pressure build-up in the swelling body due to a failing blood supply (arteriogenic disorder); (c) dysfunction of the swelling body as a result of degeneration or due to locally failing stimulus transfer (venocolytic disorder).

Age, chronic illness and the use of drugs are the most important causal factors for erectile dysfunction. Common specific factors are hypertension, smoking, diabetes mellitus, hypercholesterolemia, renal insufficiency, hypogonadism, neurological or psychiatric diseases and genitourinary interventions. In addition to medical, relational factors can also play an important role. Usually an erectile dysfunction is the result of a combination of factors.

The erection is an integral part of the sexual cycle. This cycle is subdivided into 4 stages in man: libidophase; wind and erection phase; orgasm and ejaculation phase; relaxation and de-congestion phase. Bancroft summarizes these processes with the term ‘psychosomatic circle of sex’. That it is a fixed sequence of psychological and physiological processes, indicates that disturbances in each of the phases can lead to problems in others. For example, some forms of erectile dysfunction are due to an arousal disorder due to an absent or reduced libido. Other forms are the result of premature ejaculation. Reduced libido can be the result of erectile dysfunction or ejaculatory dysfunction.

The penis is thus both sympathetic, parasympathetic and somatic innervated. The somatic innervation proceeds via the N. dorsalis penis, a terminal branch of the N. pudendus, which is composed of motor fibers for the transverse striated muscle tissue of the pelvic floor and of sensible fibers for the glans penis, the penis skin and the scrotal skin. The autonomic nerve transfer proceeds through the pelvic ganglion and the pelvic plexus, located dorsally of the bladder, where the sympathetic and the parasympathetic form a network. From there, the expansive body is innervated by numerous nerve branches.

Various neurotransmitters are released, of which nitric oxide (NO) is the most important. NO is released both to the nerve muscle synapse and to the cavernous endothelium. NO diffuses smoothly through the membrane of the cavernous smooth muscle cell without the intervention of a receptor, causing it to relax.

Relaxation of the cavernous muscle tissue forms the basis of the erection. Microscopically, the corpus cavernosum consists of a labyrinth of cavernous spaces (sinuses), which are formed by fibromuscular trabeculae, coated with endothelium. The supply of blood takes place via the paired A. pudenda interna, which originates from the A. iliaca interna. The A. cavernosa, a terminal branch of the A. pudenda interna, provides the corpus cavernosum of blood via the corkscrew-shaped Aa. helicinae that end up in the sinuses and are characterized by a thick muscular wall, with which the blood supply is regulated. In the periphery of the swelling body, below the tunica albuginea, the draining veins are located. Relaxation of the smooth muscle cells causes dilatation of the Aa. helicinae and the sinuses, which increases blood flow to the expanse of the body.

As a result, the intracavernous pressure rises and the venous drain is pinched by the stretching of the draining veins under the tunica albuginea. This leads to a decrease in venous drainage with rigidity (stiffness) as a result. In erection, the intracavernous pressure is the result of the pressure in the A. cavernosa and the resistance in the compressed veins. The swelling body is thus an arterio-venous shunt, where at rest a venous blood pressure and in erection an arterial blood pressure prevails. At rest the total blood flow in the A. cavernosa is approximately 4 ml / min. Immediately at the beginning of erection, the blood flow increases to 24 ml / min, to return to the output level in full erection. Erectile pressure above the level of systemic blood pressure results from contraction of the somatically innervated M. bulbocavernosus and M. ischiocavernosus. These also play a role in the emission of semen from the urethra during ejaculation.

How does Sildenafil help ?

Sildenafil inhibits PDE-5 and therefore the conversion of cGMP into the inactive GMP. It is rapidly absorbed after oral intake and is effective after an average of 19 min. The maximum plasma concentration is reached after 1 h. More than 95 is bound to plasma protein and the half-life is 3-5 h. Sildenafil is broken down in the liver.

The action of sildenafil differs substantially from that of the currently current drug-promoting erection-enhancing agents, because it does not activate the formation of cGMP, but potentiates its effect. This only works in patients with sexual arousal.

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Below video explains the mode of action of Sildenafil.

Side Effects

Although no long-term results are known, sildenafil seems to be an effective and safe treatment for men with erectile dysfunction. The doctor must, as with any medical treatment of erectile dysfunction, pay attention to 5 key questions during the anamnesis and the physical examination: (a) what is the complaint? (b) what is the genesis? (c) what do the patient and his partner expect? (d) what is the best treatment for this patient, and (e) what are the risks? In this context, the physician should primarily point out to the patient the cardiac risks associated with sexual exertion.

Given below are some of the major side effects.

  • an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, priapism can permanently damage your penis
  • sudden vision loss in one or both eyes Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION). Stop taking VIAGRA and call your healthcare provider right away if you have sudden vision loss in one or both eyes
  • sudden hearing decrease or hearing loss. Some people may also have ringing in their ears (tinnitus) or dizziness. If you have these symptoms, stop taking VIAGRA and contact a doctor right away

References

How does Erection happen

Sildenafil mode of action

 

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