Erectile dysfunction sildenafil

Chapter 13. PDE 5 Inhibitors for Erectile Dysfunction Sildenafil Vardenafil (Levitra ), and Tadalafil (Cialis )... 

Erectile dysfunction. Sildenafil, vardenafii, and tardalafil are inhibitors of PDE-5 and are used to promote erection. During sexual arousal NO is released from nerve endings in the corpus cavernosum of the penis, which stimulates the formation of cGMP in vascular smooth muscle. PDE-5, which is important in this tissue, breaks down cGMP, thus counteracting erection. Blockers of PDE-5 "conserve cGMP. 

Goldstein 1, Lue TF, Padma-Nathan H, Rosen RC, Steers WD, Wicker PA. Oral sildenafil in the treatment of erectile dysfunction. Sildenafil Study Group. N Engl J Med 1998 338(20) 1397-404. 

Erectile dysfunction Sildenafil (Viagra) and tadalafil (Cialis)... 

As indicated earlier, the selective PDE5 inhibitors developed for the treatment of male erectile dysfunction resulting from organic or mixed organic-psychogenic origin have been the most successful PDE inhibitors. The three marketed drugs are sildenafil, vardenafil, and tadalafil (Fig. 17.2). In addition to the treatment of erectile dysfunction, sildenafil has been indicated for the treatment of pulmonary hypertension and female sexual dysfunction. These latter uses are unlabeled uses. 

Erectile dysfunction is treated by local or systemic application of vasodilator drugs. The most effective is sildenafil, a phosphodiesterase-type 5 inhibitor. 

Recent use (within 24 h of sildenafil or vardenafil or within 48 h of tadalafil) of a phosphodiesterase-5 inhibitor for erectile dysfunction (or pulmonary hypertension)... 

Phosphodiesterase type 5 inhibitors are commonly prescribed for erectile dysfunction and include sildenafil, vardenafil,... 

Phosphodiesterase 5 inhibitors such as sildenafil are effective for MS-induced erectile dysfunction.14 In women, vaginal dryness or dyspareunia may respond to lubricating jellies. 

Gresser U, Gleiter CH. Erectile dysfunction comparison of efficacy and side effects of the PDE-5 inhibitors sildenafil, vardenafil and tadalafil review of the literature. Eur J Med Res 2002 7 435-446. 

Erectile dysfunction The addition of sildenafil or an other erectogenic drug may be helpful... 

Erectile dysfunction is common, and initial treatment should include one of the oral medications currently available (e.g., sildenafil, vardenafil,tadalafil). 

Laties, A.M., Ellis, P, and Mollon, J.D., The effects of sildenafil citrate (Viagra ) on color discrimination in volunteers and patients with erectile dysfunction, Inv. Ophthalmol. Vis. Sci., 40, S693, 1999. 

Very often, drugs are discovered through persistent work and continual optimization and many tests and trials. This is exemplified by the history behind the discovery of sildenafil (Viagra, Pfizer), a drug for the treatment of erectile dysfunction, and the AIDS drug zidovidine (Retrovir, GlaxoSmithKline) (Exhibits 3.18 and 3.19). 

At clinical trials, sildenafil did not work well as a treatment for angina. Instead, it was observed that it overcomes erectile dysfunction. Later, it was found that cyclic GMP also increases the level of nitric oxide, which is needed in penile erections. 

Hence, we can see how the focus of treatment for sildenafil changed from antihypertensive to angina treatment to overcoming erectile dysfunction, giving rise to the drug called Viagra. 

A 58-year-old man with a history of angina for which he occasionally takes isosorbide dinitrate is having erectile dysfunction. He confides in a colleague who suggests that sildenafil might help and gives him three tablets from his own prescription. The potentially lethal combination of these drugs relates to... 

One additional medication that has recently been studied is sildenafil, which is more commonly known by its trade name Viagra. Sildenafil is taken at doses from 50 to 100 mg per dose about 1-2 hours before sex. Sildenafil is sometimes effective but its expense and potential complications in patients with heart disease limit its usefulness. It can be quite useful in males who experience erectile dysfunction, though it does not improve delayed ejaculation. 

A further characteristic of this principle is that, if the activity of phosphodiesterase is decreased, the concentration of cyclic GMP will increase to an extent dependent upon the extent of the decrease in activity. This characteristic has been made use of by the pharmaceutical industry. Cyclic GMP has a vasodilatory effect and this is the case for the arterioles that supply blood to the corpus cavemosum in the penis, which controls the erection of the penis. Drugs were developed (e.g. sildenafil) that inhibits cyclic GMP phosphodiesterase and hence increases the cyclic GMP level which resnlts in vasodilation of the arterioles and an increase in the snpply of blood to the spongy tissue of the corpus cavemosum, which expands resulting in erection. This dmg has been found to be effective in some patients snffering from erectile dysfunction. This can be a particular problem in diabetic patients and more elderly men (Chapter 19). 

Patients who are using certain drugs for erectile dysfunction (eg, sildenafil citrate), because these drugs have been shown to potentiate the hypotensive effects of organic nitrates (sublingual tablets, lingual spray, transdermal). 

The safety and efficacy of combinations of sildenafil or vardenafil with other treatments for erectile dysfunction have not been studied. Therefore, the use of such combinations is not recommended. 

The moderately selective PDE type V-inhibitor sildenafil (Viagra ) has been introduced in the treatment of erectile dysfunction. On the basis of cyclic GMP accumulation sildenafil is claimed to be a selective vasodilator in erectile tissues in the penis because of the high concentration of PDE type V in this region. Several of its adverse reactions (headache, flush, hypotension) reflect its vasodilator actions in other vascular beds than that of the penis. The drug will not be further discussed here. 

Sildenafil It is orally active selective inhibitor of phosphodiesterase type 5 useful in treatment of erectile dysfunction. It results in reduced breakdown of cyclic guanosine monophosphate (cGMP) which is responsible for nitric acid (NO) mediated vasodilatation in corpora cavernosa. Thus inducing an erectile response to sexual stimulation. It has no direct relaxant effect on smooth muscle of corpus cavernosa and has no effect in absence of sexual stimulation. 

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