Tadalafil should not be used with alpha-blockers (except Flomax), medicines used to treat high blood pressure, and benign prostate hypertrophy (BPH) because the combination of tadalafil and an alpha-blocker may lower the blood pressure greatly and lead to dizziness and fainting. Examples of alpha-blockers include tamsulosin (Flomax), terazosin (Hytrin), doxazosin (Cardura), alfuzosin (Uroxatral), and prazosin (Minipress). Tamsulosin (Flomax) is the only alpha-blocker that patients can use safely with tadalafil. When tadalafil (20 mg) was given to healthy men taking 0.4 mg of Flomax daily, there was no significant decrease in blood pressure and so patients on this dose of tamsulosin (Flomax) can be prescribed tadalafil. The only alpha-blocker not tested with tadalafil is alfuzosin (Uroxatral), and no recommendations can be made regarding the interaction between the two.
The primary nerve fibers to the penis are from the dorsal nerve of the penis, a branch of the pudendal nerve. The cavernosal nerves are a part of the autonomic nervous system and incorporate both sympathetic and parasympathetic fibers. They travel posterolaterally along the prostate and enter the corpora cavernosa and corpus spongiosum to regulate blood flow during erection and detumescence. The dorsal somatic nerves are also branches of the pudendal nerves. They are primarily responsible for penile sensation. 
The great majority of ED cases in diabetic men have a physical cause, such as neuropathy or circulatory problems. In some cases, however, the cause of ED is psychological, including depression, guilt, or anxiety. With a thorough exam, the doctor should be able to determine whether the ED is psychological or physical in nature. If the cause is psychological, your doctor may refer you to a psychiatrist, psychologist, sex therapist, or marital counselor. Do not view such a diagnosis as an insult. Most psychologically-based ED is easily and successfully treated.
Diabetes is a well-recognized risk factor for ED. A systematic review and meta-analysis found that the prevalence of ED was 37.5% in type 1 diabetes, 66.3% in type 2 diabetes, and 52.5% in diabetes overall—a rate approximately 3.5 times higher than that in controls.  The etiology of ED in diabetic men probably involves both vascular and neurogenic mechanisms. Evidence indicates that establishing good glycemic control can minimize this risk.
The Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) study, designed to determine whether an individual man’s sexual outcomes after most common treatments for early-stage prostate cancer could be accurately predicted on the basis of baseline characteristics and treatment plans, found that 2 years after treatment, 177 (35%) of 511 men who underwent prostatectomy reported the ability to attain functional erections suitable for intercourse. 
Organic Impotence. Diabetes mellitus, thyroid disease, and dysfunction of the pituitary gland or testes can cause impotence, as can certain medications. Other organic causes include arterial ischemia associated with atherosclerosis of the aorta and common iliac arteries, extensive pelvic surgery such as radical prostatectomy, spinal cord injury and other neurologic disorders, and a history of cigarette smoking. Because certain medications can cause impotence, it is recommended that in cases of recent impotence it be determined whether the patient has started on a new drug. The most common offenders are diuretics, antihypertensives, and vasodilators. Alcohol, which sometimes is ignored as a drug, is often a contributor to the problem of impotence.
It is normal for a man to have five to six erections during sleep, especially during rapid eye movement (REM). Their absence may indicate a problem with nerve function or blood supply in the penis. There are two methods for measuring changes in penile rigidity and circumference during nocturnal erection: snap gauge and strain gauge. A significant proportion of men who have no sexual dysfunction nonetheless do not have regular nocturnal erections.
Diabetes. Erectile Dysfunction is common in people with diabetes. An estimated 10.9 million adult men in the U.S. have diabetes, and 35 to 50 percent of these men are impotent. The process involves premature and unusually severe hardening of the arteries. Peripheral neuropathy, with involvement of the nerves controlling erections, is commonly seen in people with diabetes.
A CVA can occur anywhere through the brain, midbrain, brainstem and spinal cord leading to varying degrees of SD depending on location. A decline in libido, erection and ejaculation are frequent in men who have had a CVA, with a reported prevalence of ED that varies from 17% to 48% (28,29). Right hemispheric infarcts seem to affect erections more so than left-sided ones. The exact effects of CVA on sexual function are complex and multifactorial, as disability, psychological and emotional status can affect sexual function aside from the location of the CVA.
These oral medications reversibly inhibit penile-specific PDE5 and enhance the nitric oxide–cGMP pathways of cavernous smooth muscle relaxation; that is, all prevent the breakdown of cGMP by PDE5. It is important to emphasize to patients that these drugs augment the body’s natural erectile mechanisms, therefore the neural and psychoemotional stimuli typically needed for arousal still need to be activated for the drugs to be efficacious.
The main surgical treatment of ED involves insertion of a penile implant (also called penile prostheses). Because penile vascular surgery is not recommended for aging males who have failed oral PDE5 inhibitors, ICI or IU therapies, implants are the next step for these patients. Although placement of a penile implant is a surgery which carries risks, they have the highest rates of success and satisfaction among ED treatment options.