The drugs work best in combination with sex therapy. Several studies have shown this. There’s more to satisfying sex than just an erection. The quality of the relationship is crucial, especially if sex has been a sore point or if the couple hasn’t had much for a while. To find a sex therapist near you, visit the American Association of Sex Educators, Counselors, and Therapists, the Society for Sex Therapy and Research, or the American Board of Sexology.
early 15c., "physical weakness," also "poverty," from Middle French impotence "weakness," from Latin impotentia "lack of control or power," from impotentem (nominative impotens); see impotent. In reference to a want of (male) sexual potency, from c.1500. The figurative senses of the word in Latin were "violence, fury, unbridled passion." Related: Impotency.
None of the ED drugs is safe to take with cardiac drugs called nitrates because it could cause a dangerous drop in blood pressure. Drugs that many men take for urinary symptoms, called alpha blockers, can also lower blood pressure, so take them at least four hours apart from ED drugs. Your doctor may start you on a smaller dose of the ED drug if you already take an alpha blocker, or may recommend the alpha blocker tamsulosin (Flomax), which affects blood pressure less.
Diet can also affect a man’s ability to achieve or maintain an erection. As stated, men who indulge in alcohol may have trouble with erections, but men who have poor diets, suffer from diabetes, or who are overweight can also restrict blood flow to the penis or suffer from poor body image. All of these factors, especially when combined, can lead to erectile dysfunction.
Alteration of NO levels is the focus of several approaches to the treatment of ED. Inhibitors of phosphodiesterase, which primarily hydrolyze cGMP type 5, provided the basis for the development of the PDE5 inhibitors. Chen et al administered oral L-arginine and reported subjective improvement in 50 men with ED.  These supplements are readily available commercially. Reported adverse effects include nausea, diarrhea, headache, flushing, numbness, and hypotension.
In a prospective study from the Prostate Cancer Prevention Trial database, Thompson et al reported that men presenting with ED had a significantly higher chance of developing a cardiovascular event over a 7-year follow-up period.  The hazard ratio was 1.45, which is in the range of risk associated with current smoking or a family history of MI.
Depression and anxiety: Psychological factors may be responsible for erectile dysfunction. These factors include stress, anxiety, guilt, depression, widower syndrome, low self-esteem, posttraumatic stress disorder, and fear of sexual failure (performance anxiety). It is also worth noting that many medications used for treatment of depression and other psychiatric disorders may cause erectile dysfunction or ejaculatory problems.
If you just got off solo, you might have to wait before you can hop into bed with your partner, says Dr. Brahmbhatt. It might have something to do with a spike in the hormone prolactin after you orgasm, according to a study published in the International Journal of Impotence Research. This hormone has been linked to difficulties maintaining an erection or even ejaculating.
Nearly every primary care physician, internist and geriatrician now understand that many older men retain an interest in sexual activity as they age. Some primary care physicians think that sexual potency in older men is the norm, and that if it is lacking, it is ‘all in the head.’ This viewpoint has not been supported by current literature. The Massachusetts Male Aging Study (MMAS) found that 52% of men between 40 and 70 years old reported having some form of erectile dysfunction (ED).1 The reality is that ED is a natural part of ageing and that the prevalence increases with age. In the MMAS, they found that roughly 50% of men at 50 years old, 60% of men at 60 years old and 70% of men at 70 years old had ED. Thus, nearly all men who live long enough should develop ED. The myths that surround the problems of impotence or ED confound the attempts of patients to receive treatment and the attempts of physicians to help them.1
The inability to achieve or sustain a sufficiently firm penile erection (tumescence) to allow normal vaginal sexual intercourse. The great majority of cases are not caused by organic disease and most men experience occasional periods of impotence. It is often related to anxiety about performance and is usually readily corrected by simple counselling methods which prescribe sensual massage but forbid coitus. Organic impotence may be caused by DIABETES, MULTIPLE SCLEROSIS, spinal cord disorders and heart disease. Many cases can be helped by the drug SILDENAFIL (Viagra).
3. An intact, anatomically correct penis; 25% of impotence may be psychologic or 'partner-specific', 25% has an organic component and 50% of impotence is organic in nature; in organic impotence, nocturnal penile tumescence is absent Management-surgical Microvascular surgery to bypass occluded vessels–most effective in younger ♂, penile prosthesis Management-medical Combined therapy with phentolamine and papaverine–self-injected by the Pt, wielding an erection of 1 hr's duration is useful for arterial, neurologic, psychogenic impotence; other therapies–zinc, bromocriptine–Parlodel, isoxsuprine-Vasodilan, Voxsuprine, nitroglycerine, yohimbine–Yocon, Yohimex Etiology Smoking, CAD, HTN, DM, medications–hypoglycemic agents, vasodilators, cardiac drugs, antihypertensives, anger and depression; it is inversely correlated to dehydroepiandrosterone, HDL-C, and an index of dominant personality Primary impotence Complete absence of successful sexual coupling Secondary impotence Priapism, penile plaques, Peyronie's disease; drugs linked to impotence: antihypertensives–eg, methyldopa, guanethidine, reserpine, clonidine, due to ↓ BP, antidepressants–eg, phenelzine, isocarboxazide, amitriptyline–causing altered moods and decreased libido, tranquilizers–eg, chlordiazepoxide and lorazepam, and the muscle-relaxing diazepam, cimetidine, which ↑ prolactin, and is associated with impotence and loss of libido. Cf Infertility, Orgasmic dysfunction.
Another study compared the response of surgically and medically castrated rabbits to vardenafil with that of control rabbits.  Castrated rabbits did not respond to vardenafil, whereas noncastrated rabbits did respond appropriately. This result suggests that a minimum amount of testosterone is necessary for PDE5 inhibitors to produce an erection.
ED usually has something physical behind it, particularly in older men. But psychological factors can be a factor in many cases of ED. Experts say stress, depression, poor self-esteem, and performance anxiety can short-circuit the process that leads to an erection. These factors can also make the problem worse in men whose ED stems from something physical.