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Aging: There are two reasons why older men are more likely to experience erectile dysfunction than younger men. First, older men are more likely to develop diseases (such as heart attacks, angina, cardiovascular disease, strokes, diabetes mellitus, and high blood pressure) that are associated with erectile dysfunction. Second, the aging process alone can cause erectile dysfunction in some men, primarily by decreasing the compliance of the tissues in the corpora cavernosa, although it has been suggested, but not proven, that there is also decreased production of nitric oxide in the nerves that innervate the corporal smooth muscle within the penis. buy genuine kamagra online kamagra online pharmacy Before starting sildenafil for erectile dysfunction, a doctor may need to determine whether the heart can safely achieve the workload necessary for sexual activity. For example, in men with coronary artery heart disease, a doctor may perform a treadmill stress test to determine whether there is adequate blood supply to the heart muscle while exercising at levels comparable to sexual activity. Buy viagra us Modern drug therapy for ED made a significant advance in 1983, when British physiologist Giles Brindley, Ph.D. dropped his trousers and demonstrated to a shocked Urodynamics Society audience his papaverine-induced erection.[33] The drug Brindley injected into his penis was a non-specific vasodilator, an alpha-blocking agent, and the mechanism of action was clearly corporal smooth muscle relaxation. The effect that Brindley discovered established the fundamentals for the later development of specific, safe, orally effective drug therapies.[34][better source needed][35][better source needed] Therefore, men with these conditions should not use vardenafil without having these conditions evaluated and stabilized first. For example, men with uncontrolled high blood pressure should have their blood pressure controlled; and men with potentially life-threatening abnormal heart rhythms should have these rhythms controlled. generic viagra for sale online buy viagra online order generic viagra online uk viagra online without prescription "Age-associated erectile dysfunction involves a decrease in nitric oxide availability and impaired relaxation," wrote scientists who found a potential treatment for erectile dysfunction in spider venom, a toxin that boosts available nitric oxide. Substance abuse: Marijuana, heroin, cocaine, methamphetamines, crystal meth, and alcohol abuse contribute to erectile dysfunction. Alcoholism, in addition to causing nerve damage, can lead to atrophy (shrinking) of the testicles and lower testosterone levels. Therefore, men with these conditions should not use tadalafil without having these conditions evaluated and stabilized first. For example, men with uncontrolled high blood pressure should have their blood pressure controlled; and men with potentially life-threatening abnormal heart rhythms should have these rhythms controlled.