There are no oral drugs that are legally prescribable to help the formation of erections. Certain combinations of drugs of abuse can be erection-enhancing but carry potential dangerous side effects. The drugs most commonly used are injected and work by constricting the venous blood vessels. This allows blood into the penis but not out, thereby creating an erection. These will last for a few hours and are not reversible, a little painful to give and the erections may ache. These drugs can only be offered after review by specialists and are worth a try if alternative measures have not worked.