Viagra in medical store

Effects of shock strengths on ventricular defibrillation failure.

Sildenafil in patients with cardiovascular disease.

Alternative projections of mortality and disability by cause 1990-2020: Global Burden of Disease Study.

Alloggiamento T, Zipp C, Raxwal VK, Ashley E, Dey S, Levine S & Froelicher VF (2001). Padma-Nathan H, Eardley I, Kloner RA, Laties AM & Montorsi F (2002). A 4-year update on the safety of sildenafil citrate (Viagra). McGovern PG, Jacobs Jr DR, Shahar E, Arnett DK, Folsom AR, Blackburn H & Luepker RV (2001).

Trends in acute coronary heart disease mortality, morbidity, and medical care from 1985 through 1997: the Minnesota heart survey. Sildenafil: a 4-year update in the treatment of 20 million erectile dysfunction patients.

Geelen P, Drolet B, Rail J, Berube J, Daleau P, Rousseau G, Cardinal R, O'Hara GE & Turgeon J (2000). Sildenafil (Viagra) prolongs cardiac

repolarization

Swissa M, Ohara T, Lee MH, Kaul S, Shah PK, Hayashi H, Chen PS & Karagueuzian HS (2002).

Sildenafil-nitric oxide donor combination promotes ventricular tachyarrhythmias in the swine right ventricle.

Vardi Y, Bulus M, Reisner S, Nassar S, Aboud L, Sprecher E & Gruenwald I (2003). Effects of sildenafil citrate (Viagra) on hemodynamic parameters during exercise testing and occurrence of ventricular arrhythmias in patients with erectile dysfunction and cardiovascular disease.

Kaya D, Guler C, Esen AM, Barutcu I & Dincel C (2004).

Sildenafil citrate does not alter ventricular repolarization properties: novel evidence from dynamic QT

analysis

Annals of Noninvasive Electrocardiology , 9: 228-233.

Sildenafil (Viagra) reduces arrhythmia severity during ischaemia 24 h after oral administration in dogs. Preconditioning with ischemia: a delay of lethal cell injury in ischemic myocardium. Sildenafil induces delayed preconditioning through inducible nitric oxide synthase-dependent pathway in mouse heart. Das S, Maulik N, Das DK, Kadowitz PJ & Bivalacqua TJ (2002).

Cardioprotection with sildenafil, a selective inhibitor of cyclic 3',5'-monophosphate-specific phosphodiesterase 5. Drugs under Experimental and Clinical Research , 28: 213-219.

Effects of sildenafil on myocardial infarct size, microvascular function, and acute ischemic left ventricular dilation.

Ockaili R, Salloum F, Hawkins J & Kukreja RC (2002). Sildenafil (Viagra) induces powerful cardioprotective effect via opening of mitochondrial K(ATP) channels in rabbits.

The pharmacology of sildenafil, a novel and selective inhibitor of phosphodiesterase (PDE) type 5.

Japanese Journal of Pharmacology , 114 (Suppl 1): 22P-26P. Late preconditioning elicited by activation of adenosine A(3)

receptor

Chattipakorn, Cardiac Electrophysiology Unit, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand. Research supported in part by the Thailand Research Fund (TRF) grant RSA4680010 (N. Chattipakorn) and the funding from the China Medical Board, Faculty of Medicine, Chiang Mai University (N.

All the contents of this journal, except where

otherwise

Armenio Costa Guimaraes, Marcus Vinicius Bolivar Malachias, Otavio Rizzi Coelho, Emilio Cesar Zilli, Rafael Leite Luna.

Erectile dysfunction, formerly called impotence, is the inability of the male to achieve or maintain penile erection and thus engage in coitus 1 .

It is common among patients with cardiovascular diseases or their risk factors. This dysfunction occurs mainly among individuals with coronary artery disease, after episodes of acute ischemic syndrome, hypertensive patients underpharmacologic treatment, and viagra in medical store among patients with heart failure. In approximately 85% of these cases, the fear of a cardiac event during coitus constitutes an important factor for erectile dysfunction 2-4 . Discovery of sildenafil citrate has represented a great development in the treatment of erectile dysfunction; it may benefit, among many others, those patients with cardiovascular diseases or with their risk factors 5 .

Even though clinical trials including more than 3,700 patients with viagra in medical store erectile dysfunction, 2,000 of them in controlled studies with placebo, have shown a good tolerance for the medication, more intense circulatory side effects may occur in individuals with

cardiovascular

These circumstances require recommendations by specialists so that sildenafil can be safely used.

In the Massachusetts Male Aging Study (MMAS), erectile dysfunction significantly correlated with 3 groups of diseases: atherosclerosis, hypertension, and diabetes mellitus 7 .

The most important organic factor involved in this dysfunction is impairment of penile blood flow, common in men above 50 years of age with atherosclerosis or diabetes.

It is estimated that 50% (ranging from

28%

The erectile action of sildenafil combines increase in

arterial

Sildenafil leads to relaxation of smooth muscle of penile arteries and trabeculae surrounding the sinusoidal spaces, resulting in a greater engorgement of cavernous body. The trabeculae of engorged sinusoidal spaces compress the penile venules against the tunica albuginea, reducing venous flow, contributing to maintenance of engorgement of cavernous body 8 . Relaxation of this smooth muscle results from a decrease in intracellular calcium mediated by accumulation of the second messenger, the cyclic guanosine monophosphate (cGMP), whose production results from activation of guanyl cyclase by nitric oxide produced by the stimulus of endothelial cells generated by sexual desire. The limiting factor in this process is degradation of cGMP by the enzyme 5 phosphodiesterase (PDE5) present in high concentrations in the penile structures.

Sildenafil facilitates

erection

Lower concentrations of PDE5 may also viagra in medical store be found in the smooth muscle of arteries in general, of viscera and trachea, and in platelets.

Seven types of phosphodiesterases have already been identified.

Sildenafil has a lower inhibiting power upon other isoenzymes of phosphodiesterase as compared with PDE5.

It has a weak selectivity (1,000 times smaller) for PDE2 (predominates in the adrenal cortex), PDE3 (smooth muscle, platelets and myocardium), and PDE4 (lymphocytes of the brain and lungs). It has a moderate selectivity (80 or more times smaller) for PDE1 (predominates in the brain, kidneys and smooth muscle) and an only 10-times smaller selectivity for PDE6 (photoreceptors of the retina), the probable cause of visual disorders that may occur with viagra in medical store the use of sildenafil.

The 4,000-times lower selectivity for PDE3 (involved in myocardial contractility) is important because the inhibitors of this isoenzyme (milrinone, vesnarinone, and enoximone) used for treating heart failure cause cardiac arrhythmia and have other noxious effects 8,10 . The peak of plasma concentration of sildenafil occurs 30 to 120 minutes (mean of 60 minutes) after oral ingestion, during fasting.

In the liver, sildenafil is partially converted into a metabolite that accounts for approximately 20% of its pharmacological action, and both circulate almost completely bound to plasma proteins (96%). The major hepatic metabolic pathways are viagra in medical store the cytochrome P450 3A4 (main) and P450 2C9 (secondary) 8,11 .

Excretion is predominantly fecal (80%); only 13% are urinary.

For a given oral dose of sildenafil, plasma concentrations of the drug may be 40% higher in individuals above 65 years of age, 80%

higher

Effect on penile tumescence ? Sildenafil is effective in erectile dysfunction of various causes, such as vascular (diabetes), neuroreflexogenic (spinal cord damage), and psychogenic, which has been confirmed in 21 multicenter double-blind randomized trials controlled with placebo 11,12 .

Cardiovascular effects ? 1) Sildenafil does not interfere with myocardial contractility in healthy volunteers. However, studies in patients with heart failure are still lacking; 2) Sildenafil causes a mild and transient drop in systolic (8 to 10 mmHg) and diastolic (4 to 6 mmHg) blood pressures, with a peak one hour after the oral dose, ingested during fasting, returning to the baseline in 4 hours. This effect results from the peripheral arterial and

venous