Erectile dysfunction (ED or impotence) is a common medical condition affecting many men world wide. The most commonly used treatment for ED are oral medications like Viagra (sildenafil), Levitra (vardenafil) and Cialis (tadalafil). If these are not effective the use of an injection into the penis (intracavernosal injection or ICI) is necessary. However in some men neither of these therapies is successful.

Hypothesis: An adequate erection may be achieved in men with difficult-to-treat erectile dysfunction, when they are treated with a therapy of combination of tablet and penile injection, when a single treatment therapy has failed for these men.

Aim of the study is to test the safety and efficacy of a combination of Viagra and Caverjet Impulse in a group of men who had failed to achieve an adequate response to the maximum recommended dose of either Viagra, Cialis or Levitra and Caverjet Impulse, when these treatments were used alone.

20 men with difficult to treat ED will be given oral medication, intracavernosal therapy or the combination in a single-blind randomised study.

Informed consent will be signed prior to any study procedures being carried out. All participants are 'blinded' to their study treatments. Participants who have satisfactory response to any of the tablets or penile injections, will be excluded from the study.

Inclusion Criteria:

• Men aged 20 years and over
• History of ED for at least 6 months
• IIEF score <26
• Failure to achieve an adequate response to the maximum recommended therapeutic dose of an approved ED treatments, when either of these treatments was used alone.

Exclusion Criteria:

• Concurrent treatment with nitrate-containing medications
• Significant cardiac, hepatic, renal or respiratory dysfunction
• Systolic blood pressure of less than 100mm Hg
• Myocardial infarction, serious cardiac arrhythmia, cardiac surgery, or stroke within the last 6 months
• Significant penile fibrosis, curvature or infection
• Reported significant side effects of using PDE5 inhibitors or alprostadil
• Hypersensitivity to PDE5 inhibitors or alprostadil