It is recommended that its allotting be done only through a prescription, considering that the foremost number of men who put it to use have a further underlying diagnosis and, therefore , could be applying other prescription drugs simultaneously, which could interact with Sildenafil increasing the vasodilatory effect7, 10 and, therefore , the adverse effects. A report, published in 'Frontiers in Neurology', alerts of the likely risks of persistent visual side effects, such as sensitivity to light and deterioration of color eyesight, in males who have used the highest suggested dose of Viagra. PDF5 blockers sildenafil, tadalafil, vardenafil improve the availability of cGMP and are the most effective medications for treating ED. Men uncertain? Power, do the job and making love, 2001 In superior ventricular arrhythmias in referred to coronary individuals, with heart and soul failure or with syncope, it should certainly not be used.