ABSTRACT
To say that sildenafil has transformed the management of ED would be a substantial understatement. Its mechanism of action by blocking PDE5’s degradation of cGMP promotes blood flow into the penis (see Figure 3.2, page 9) and the restoration of erectile function. Vardenafil and tadalafil have recently been added to this family of drugs. Because their mechanism of action is the same, there is no reason to assume there will be any significant differences in ED effectiveness; however, their PDE selectivity and half-life may be of clinical importance. Potency is not clinically relevant, because it is a way of expressing in vitro concentrations of a drug – in short, given in dose equivalents the clinical end-point will be the same.
