Rodja is right. You will only gain at the top end 25% product absorbtion, whilst oral is much higher than that for these products. It is much slower to enter the blood stream actually, with a slower release of upward of 12 hours. You want bang for these products, so oral is the way to go. Plus, slathering yourself up with PDE5 inhibitors then going for a naked roll in the sheets with your lady friend may not be a good idea due to transfer.