I have no idea why your boyfriend's junk is stuck in the junkyard. He's just 25, in the prime of his penis. It's fairly rare for a guy that young to go from instant erection to shy willy. One study found that just 2 percent of men experienced erectile dysfunction before the age of 40. If it's a short-term thing, it could be simple: Maybe he just needs to get more sleep or have fewer drinks.
Dr. Liou says that some men come to him after getting a prescription from their primary care doctors, claiming that the drug doesn't work. Sometimes it's because they used it incorrectly. "The biggest misconception is that these drugs are an on/off switch for erections," Dr. Liou says. But the drugs don't work well without sexual stimulation. "During that time, you need to be with your partner and have foreplay," Dr. Liou says. "Don't take it, do the taxes or the dishes, and then meet at the bedroom thinking you'll be ready to go. It's not like that."
Aging, liver and kidney problems, and concurrent use of certain medications (such as erythromycin [an antibiotic] and protease inhibitors for HIV) slows the metabolism (breakdown) of sildenafil. Slowed breakdown allows sildenafil to accumulate in the body and potentially may increase the risk of side effects. Therefore, in men over 65 years of age, in men with significant kidney and liver disease, and in men who also are taking medications called protease inhibitors, the doctor will initiate sildenafil at a lower dose (25 mg) to avoid accumulation of sildenafil in the body. A protease inhibitor ritonavir (Norvir) is especially potent in increasing the accumulation of sildenafil, thus men who are taking Norvir should not take sildenafil doses higher than 25 mg and at a frequency of no greater than once in 48 hours. Other medications that may affect the level of sildenafil include erythromycin and ketoconazole.
In other cases, men who habitually use alcohol or other drugs may experience similar results. Alcohol is a depressant to the central nervous system. This means that a little bit might be able to lighten the mood, but too much can basically shut down all communication between the brain and the penis. When this happens, no amount of will or stimulation will result in an erection. Other drugs can also affect the body’s ability to achieve an erection, including heroin and MDMA, otherwise known as ecstasy.
Diabetes is an example of an endocrine disease that can cause a person to experience impotence. Diabetes affects the body’s ability to utilize the hormone insulin. One of the side effects associated with chronic diabetes is nerve damage. This affects penis sensations. Other complications associated with diabetes are impaired blood flow and hormone levels. Both of these factors can contribute to impotence.
Sexual dysfunction is highly prevalent in men and women. In the MMAS, 52% of the respondents reported some degree of erectile difficulty. Complete ED, defined as (1) the total inability to obtain or maintain an erection during sexual stimulation and (2) the absence of nocturnal erections, occurred in 10% of the respondents. Mild and moderate ED occurred in 17% and 25% of responders, respectively. 
Diabetes mellitus: Erectile dysfunction tends to develop 10 to 15 years earlier in diabetic men than among nondiabetic men. The increased risk of erectile dysfunction among men with diabetes mellitus may be due to the earlier onset and greater severity of atherosclerosis (hardening of the arteries) that narrows the arteries and thereby reduces the delivery of blood to the penis. Atherosclerosis can affect the arteries in the penis, as well as the arteries in the pelvis that supply the penile arteries. Diabetes mellitus also causes erectile dysfunction by damaging nerves that go to the penis, much like the effect of diabetes on nerves in other areas of the body (diabetic neuropathy). Diabetes can also affect the muscles in the penis, leading to troubles with erections. Smoking cigarettes, obesity, poor control of blood glucose levels, and having diabetes mellitus for a long time further increase the risk of erectile dysfunction in people with diabetes.
An approach to the diagnosis and management of the impotent patient is presented in Figure 187.1. Apparent and likely causes of impotence should be considered first and, if possible, eliminated before the work-up continues. For instance, observing the patient for a few weeks off offending medication may be all that is necessary to establish the cause of impotence. When no obvious or remediable cause is present, the next step is based on the clinical impression of the likelihood of organic versus psychologic impotence. If the latter is considered more likely, it is perfectly reasonable to refer the patient directly for sexual therapy, with the option of reconsidering the diagnosis if, after appropriate therapy, there is no improvement. While an occasional patient with organic impotence will be misrouted, many more with psychogenic impotence will be spared an unnecessary and costly evaluation for organic causes. When organic impotence is likely, a serum testosterone level is the initial screening test for hypogonadism and should be obtained prior to urologic referral. Patients with low testosterone levels require further endocrine evaluations as depicted in Figure 187.1.
Then you have to be able to make the right diagnosis. What is the basis for their erectile dysfunction? Is it psychogenic? Is it some sort of neurological or blood vessel or hormonal issue? So you have to make a diagnosis. You have to be able to make an assessment. And then only after those things are done, then you start to think about medications.
Your question reminds me of this brilliant Louis CK bit from his special Hilarious, in which he talks about a guy who said his appetizer was amazing. "Really? You were amazed by a basket of chicken wings? What if Jesus comes down from the sky and makes love to you all night long and leaves the new living lord in your belly? What are you going to call that? You used amazing on a basket of chicken wings! You've limited yourself verbally to a shit life."
Under normal circumstances, when a man is sexually stimulated, his brain sends a message down the spinal cord and into the nerves of the penis. The nerve endings in the penis release chemical messengers, called neurotransmitters, that signal the corpora cavernosa (the two spongy rods of tissue that span the length of the penis) to relax and fill with blood. As they expand, the corpora cavernosa close off other veins that would normally drain blood from the penis. As the penis becomes engorged with blood, it enlarges and stiffens, causing an erection. Problems with blood vessels, nerves, or tissues of the penis can interfere with an erection.
In a prospective, multicenter, single-armed study of ED patients who exhibited a suboptimal response to PDE5 inhibitors, the investigators found that percutaneous implantation of zotarolimus-eluting stents in focal atherosclerotic lesions was both safe and feasible and was associated with clinically meaningful improvement on subjective and objective measures of erectile function. 
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.
The main medical causes of erectile dysfunction are based around poor blood flow (due to furring of the arteries thanks to raised cholesterol or high blood pressure), poor nerve supply caused by diabetes-related nerve damage, or low testosterone as a result of obesity, old age or failing gonads. We doctors get just as concerned with men who have variable erections as well as those that can't get an erection at all. Failing to get an erection occasionally is pretty normal as you get older. But if you have unreliable erections for a prolonged period of time – more than six months – this could suggest an early sign of physical problems such as cardiovascular disease or diabetes which could develop further so get yourself checked out.
It is estimated that up to 20 million American men frequently suffer from impotence and that it strikes up to half of all men between the ages of 40 and 70. Doctors used to think that most cases of impotence were psychological in origin, but they now recognize that, at least in older men, physical causes may play a primary role in 60% or more of all cases. In men over the age of 60, the leading cause is atherosclerosis, or narrowing of the arteries, which can restrict the flow of blood to the penis. Injury or disease of the connective tissue, such as Peyronie's disease, may prevent the corpora cavernosa from completely expanding. Damage to the nerves of the penis, from certain types of surgery or neurological conditions, such as Parkinson's disease or multiple sclerosis, may also cause impotence. Men with diabetes are especially at risk for impotence because of their high risk of both atherosclerosis and a nerve disease called diabetic neuropathy.
Experts often treat psychologically based impotence using techniques that decrease anxiety associated with intercourse. The patient's partner can help apply the techniques, which include gradual development of intimacy and stimulation. Such techniques also can help relieve anxiety during treatment of physical impotence. If these simple behavioral methods at home are ineffective, a doctor may refer an individual to a sex counselor.
Having learned a great deal more about erectile dysfunction including its risk factors and causes, you should be equipped to assess your own erectile function. If you have experienced erectile issues or you have some of the risk factors mentioned above, it may be worth making a trip to your doctor’s office. If you choose to seek help, give your doctor as much information as you can about your symptoms including their frequency and severity as well as the onset. With your doctor’s help, you can determine the best course of treatment to restore sexual function.
First realize that this is normal, and just because it happened once does not mean it will happen again (but freaking out about it could make it happen again). Then Skyler tells people to completely ditch the idea that sex is a goal-oriented act with orgasm being the big finish. Instead, take a pleasure-oriented mentality where various sex acts are done because they feel good — not because it's part of series of steps to get you to climax. This helps take away some of the anxiety, because when you're not so focused on the performance, it's not that big of a deal if there's a little bit of stage fright, she says. There's plenty of other things you can do while hanging out with a non-erect penis!
Thanks to over a decade of primetime television commercials, most of us can name at least one drug that treats erectile problems. However, far fewer of us can name drugs that may actually cause the problem. In reality, MedlinePlus reported that there are far more of these, and even common drugs such those to treat depression and heartburn can make it difficult to get an erection.
Sildenafil (Viagra) was the first oral phosphodiesterase type 5 (PDE5) inhibitor approved by the FDA in the United States for the treatment of erectile dysfunction (it is not approved for women). Sildenafil inhibits PDE5, which is an enzyme that destroys cGMP. By inhibiting the destruction of cGMP by PDE5, sildenafil allows cGMP to accumulate. The cGMP in turn prolongs relaxation of the smooth muscle of the corpora cavernosa. Relaxation of the corpora cavernosa smooth muscle allows blood to flow into the penis resulting in increased engorgement of the penis. In short, sildenafil increases blood flow into the penis and decreases blood flow out of the penis.
Lifestyle choices that impair blood circulation can contribute to ED. Smoking, excessive drinking, and drug abuse may damage the blood vessels and reduce blood flow to the penis. Smoking makes men with atherosclerosis particularly vulnerable to ED. Being overweight and getting too little exercise also contribute to ED. Studies indicate that men who exercise regularly have a lower risk of ED.