Soler et al. compared sildenafil to vardenafil and tadalafil (69). Sildenafil was effective in 85% of SCI patients, 74% of the patients on vardenafil and 72% of the patients on tadalafil. Sildenafil was associated with more rigid and longer lasting erections. Additionally, 50 mg of sildenafil was effective in 55% of patients compared to more than 70% of the patients on vardenafil and tadalafil requiring 20 mg for a similar response. Men who used tadalafil were able to achieve erections 24 hours after administration, improving overall satisfaction related to the possible spontaneity of sexual encounters. Del Popolo also evaluated the time/duration effectiveness of PDE5i sildenafil 50 mg versus tadalafil 10 mg (64). Tadalafil 10 mg significantly increased the percentage of successful intercourse attempts at 12–24 hours compared with sildenafil. One can suspect that vardenafil, which has a longer half-life than sildenafil, could offer a similar benefit but a study investigating this occurrence has yet to be performed.
PDE5 inhibitors, the primary second-line therapy, have been the mainstay of ED treatment since the release of sildenafil (Viagra) in 1998, with the subsequent development of many others, and still more in the development stage. These medications do improve erectile quality for the majority of men, and they work by enhancing blood flow in the corpora cavernosa. These medications are generally used on demand and need to be taken about an hour before sexual intimacy. Tadalafil (Cialis) is longer acting and does come in a daily preparation potentially eliminating the ‘on-demand’ need. The daily dosing of tadalafil, 2.5–5 mg\day, has also been approved by the FDA for treatment of symptoms of BPH.41 PDE5 inhibitors are contraindicated in men taking nitrates, but otherwise PDE5 inhibitors are very safe and effective. When PDE5 inhibitors are coadministered with nitrates, pronounced systemic vasodilation and severe hypotension are possible. Many patients with ED are elderly and have the same risk factors as patients with CAD, so these drug combinations are commonly considered or encountered in clinical practice.42
Since sexual arousal is a complex process involving hormones, emotions, nerves, muscles, blood vessels and the brain, a malfunction in any of these can lead to ED. Stress, exhaustion and psychological issues can also contribute, and anxiety over maintaining an erection can actually make it harder to attain. In short, any condition that inhibits blood flow to the penis can lead to ED.

A physical exam checks your total health. Examination focusing on your genitals (penis and testicles) is often done to check for ED. Based on your age and risk factors, the exam may also focus on your heart and blood system: heart, peripheral pulses and blood pressure. Based on your age and family history your doctor may do a rectal exam to check the prostate. These tests are not painful. Most patients do not need a lot of testing before starting treatment.

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