This drug is taken in tablet form one hour before sexual activity to help men treat erection problems. It then remains active for three to four hours. Viagra won't work without sexual stimulation. It's not an aphrodisiac and doesn't increase sexual desire. The problem is that it doesn't provide immediate effect - and sometimes you may need an instant erection!

Some men should not take PDE5 inhibitors. They can cause hypotension (abnormally low blood pressure that can lead to fainting and even shock) when given to patients who are taking nitrates (medications taken for heart disease). Therefore, patients taking nitrates daily should not take any of the PDE5 inhibitors. Nitrates relieve angina (chest pain due to insufficient blood supply to the heart muscle because of narrowing of the coronary arteries); these include nitroglycerine tablets, patches, ointments, sprays, and pastes, as well as isosorbide dinitrate and isosorbide mononitrate. Other nitrates such as amyl nitrate and butyl nitrate also are in some recreational drugs called "poppers."

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.
NO is produced by the enzyme NO synthase (NOS). [13] NOS plays many roles, ranging from homeostasis to immune system regulation. To date, 3 subtypes have been identified: nNOS, iNOS, and eNOS, which are produced by the genes NOS1, NOS2, and NOS3, respectively. This nomenclature is derived from the sources of the original isolates: neuronal tissue (nNOS), immunoactivated macrophage cell lines (iNOS), and vascular endothelium (eNOS). The subtypes are not, however, limited to the tissues from which they were first isolated.
Name of DrugWhen to TakeDoseDietary RestrictionsViagraTake between 30 and 60 minutes (and up to 4 hours) before sex; works for about 4 hoursRecommended dose for most men is 50mgs; after that, dosage may go to as high as 100mg, or as low as 25mg, which may be prescribed for men over 65.Quickly absorbed by the body, less effective after a high-fat meal, and best taken on an empty stomach.Name of DrugWhen to TakeDoseDietary RestrictionsLevitraTake 1 hour before sex; works for 4 to 5 hours, and may be slightly more effective than ViagraStarting dose for most men is 10mgs a day, but men over 65 often start on the 5mg pill.Can be taken with or without food, although slightly less effective after a high-fat meal.  Avoid anything containing grapefruit juice; it may make side effects worse.Name of DrugWhen to TakeDoseDietary RestrictionsCialisComes in two forms. The daily pill stays effective in between doses, but may take 4 to 5 days before it begins working. The “weekender” version of Cialis can start working in as little as 30 minutes for men who take the highest dose of the drug (20mgs); it stays effective in the body for up for 36 hours.Daily pill comes in both a 2.5mg and 5mg tablet; most men start with the lower dose. The use-as-needed, “weekender” pill comes in 5, 10 and 20mg strengths; recommended starting dose is 10mg,Can be taken with or without food.   Avoid heavy drinking (5 glasses of wine or 5 shots of whiskey); when combined with Cialis, it can lead to headaches, dizziness, an increase in heart rate, and a drop in blood pressure.Name of DrugWhen to TakeDoseDietary RestrictionsStaxyn Take 1 hour before sex, although many men report erections in 20 to 30 minutes.  Because Staxyn comes in a sleek black package and is taken as a rapidly dissolving tablet (without water), some men think of it as a more discrete way to treat ED.Comes in 10mg tablets; do not take more than 1 a day.Avoid taking it with any kind of liquid. Should be placed directly on the tongue and allowed to dissolve without chewing.Name of DrugWhen to TakeDoseDietary RestrictionsStendraPrescribing information now recommends taking it 30 minutes before sex. Some men, however, report results in as little as 10 to 12 minutes, depending on the dose. Because of these findings, Auxilium Pharmaceuticals, the Chesterbrook, Pa., company that has U.S. marketing rights to the drug, has asked the FDA to revise the prescribing information.Starting dose is 100mgs for most men, but the 50mg tablet is recommended for men taking alpha-blocker drugs, like those used for high blood pressure and prostate problems.May be taken with or without food, and with a moderate amount of alcohol (3 drinks).   Drinking more than that can increase the chances of side effects like rapid heart rate, low blood pressure, dizziness and headaches.Name of DrugWhen to TakeDoseDietary RestrictionsPenile injections & the MUSE suppositoryTake 5 to 10 minutes before planning to have sex; erections last for 30 to 60 minutes.MUSE comes in 4 dosage strengths; most men start at 125mgs. Avoid taking more than twice within a 24-hour period.N/A
PDE 5 inhibitors are broken down primarily by enzyme, cytochrome P450enzyme CYP3A4. Medications that decrease or increase the activity of CYP3A4 may affect levels and effectiveness of PDE 5 inhibitors. Such drugs include medications for the treatment of HIV (protease inhibitors) and the antifungal medications ketoconazole and itraconazole. Thus caution is recommended.
Psychosexual counselling, or sex therapy, is an appropriate recommendation especially for men who are experiencing discord with their partner especially if the conflict is related to the man’s ED. Counselling usually consists of 5–20 sessions with counsellor. It is our recommendation that referral doctors treating men with ED make a referral to a psychotherapist or sex therapist who is certified by AASECT (American Association of Sexuality Educators, Counselors and Therapists) of certified sexuality educator.43

Unfortunately, some patients may have an overly simplified understanding of the role of PDE5 inhibitors in ED management. Such patients may not expect or be willing to undergo a long evaluation and testing process to obtain a better understanding of their sexual problem, and they may be less likely to involve their partner in discussing their sexual relationship with the physician. They may expect to obtain medications through a phone call to their doctor or even over the Internet, with minimal or no physician contact at all.
While impotence may be the presenting symptom of vascular disease, in neurologic disease impotence generally occurs in the setting of an obvious nervous system disorder, typically in patients known to have spinal cord pathology or neuropathy. Impotent patients should be questioned about decreased genital sensation, which would suggest diabetic, alcoholic, or other forms of neuropathy; weakness, which may accompany multiple sclerosis or spinal cord tumors; and back pain, bowel, and bladder symptoms, which raise concern for cauda equina syndrome. A careful drug history is important in the evaluation of impotence. Drugs that cause impotence (Table 187.3) generally do so by interfering with neurotransmission.
Little is known about the natural history of erectile dysfunction. This includes information on the age of onset, incidence rates stratified by age, progression of the condition, and frequency of spontaneous recovery. There also are very limited data on associated morbidity and functional impairment. To date, the data are predominantly available for whites, with other racial and ethnic populations represented only in smaller numbers that do not permit analysis of these issues as a function of race or ethnicity.

When sexually stimulated there is a release of a chemical, nitric oxide (NO) in the blood vessels of the corpus cavernosum. The NO stimulates the production of a compound called cGMP, which causes relaxation of the smooth muscle in the blood vessels supplying the corpus cavernosum. PDE 5 is an enzyme that breaks down cGMP. By inhibiting the breakdown of cGMP by PDE5, these medications allow cGMP to build up in the penis. cGMP causes muscles in the corpora cavernosa of the penis to relax. When the muscle is relaxed, more blood can flow into the penis and fill the spaces in the penis. As the penis fills with blood, the veins in the penis are compressed, and this results a hard erection. When the effect on PDE5 decreases, the cGMP levels go down and the muscle in the penis contracts, causing less blood to flow into the penis and allowing the veins to open up and drain blood out of the penis.
By contrast, psychogenic impotence typically is abrupt in onset, often in relation to psychological trauma, and may wax and wane. Patients with psychogenic impotence may have total erectile failure with one partner but not another, or be impotent during sexual intercourse but not during self-stimulation. Normally occurring spontaneous erections in the morning suggest psychogenic rather than organic causes for 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.
Remember those cultural messages we discussed earlier, about how men are wild sex aliens from the planet Weenus? Well, men are raised hearing those messages, too, and they can end up screwing with their sexual self-image —for instance, they can lead men to obsess over their own virility, and panic about impressing a new partner, until they've thought their boner into a corner and can't get an erection. Performance anxiety is one of the most common culprits behind lost erections, especially among younger, less experienced men.
The time the dose should be taken and how long the effects last depend on the medication used. The most common side effect of these medications is a headache. However, there is a potential for certain dangerous drug interactions. Anyone prescribed this medication must let his doctor know about any medications he's on, and especially if he's taking nitrates (e.g., nitroglycerin spray, nitroglycerin pills, or nitroglycerin patch) for heart problems.
In addition to Viagra, other ED drugs available in the United States include avanafil (Stendra), tadalafil (Cialis) and vardenafil (Levitra). These all improve blood supply to the penis. In combination with sexual stimulation, the drugs can produce an erection sufficient to initiate and complete intercourse. There is also a fast-dissolving form of Levitra, called Staxyn, that you put under your tongue.

Neurologic impotence is suggested by the absence of sensation in the sacral dermatomes when tested by pinprick, or by neurologic abnormalities elsewhere. The bulbocavernosus reflex may be assumed to be present if anal sphincter tone is normal on rectal examination. If there is doubt, the reflex can be tested by pinching the glans penis and assessing sphincter contraction during the rectal examination.
A meta-analysis of 36 744 men with ED in 12 prospective cohort studies found that the presence of ED significantly increased the risk of CVD, CAD, stroke and all-cause mortality, and the presence of ED was an independent risk factor for CVD. Ponholzer et al found that men with moderate to severe ED had a 65% increased relative risk for developing symptomatic CAD compared with men who did not have ED.26
How soon the drugs start working ranges from 15 to 60 minutes. Neither Viagra nor Levitra will work if you take them after a meal, which blocks their absorption. However, neither Cialis nor Stendra interact with food this way. The onset time determines how soon you can engage in intercourse. Stendra and daily-use Cialis are closest to being an "on demand" erectile drug; using the others requires more planning.
All these treatments listed above do not provide immediate effect on your body. If you need an instant erection, you should take a look at the topical erection treatment. Targeted delivery has been recently identified as an emerging alternative to orally administered products mainly due to the current concerns of the side effects that may occur from taking prescription drugs. Topical erection treatment presents a preferable delivery method to get an erection that enhances the desired effect directly to the intended site of action while limiting the exposure of the rest of the body to the ingredients.
If you are taking medications (alpha-blockers) for problems with an enlarged prostate, you should discuss your prostate medications with your doctor. Alpha-blockers also can cause lowering of the blood pressure. Thus your doctor will need to carefully watch your blood pressure when you start the PDE5 inhibitor. Common alpha-blockers include doxazosin (Cardura), terazosin (Hytrin), and tamsulosin (Flomax).
Vacuum devices for ED, also called pumps, offer an alternative to medication. The penis is placed inside a cylinder. A pump draws air out of the cylinder, creating a partial vacuum around the penis. This causes it to fill with blood, leading to an erection. An elastic band worn around the base of the penis maintains the erection during intercourse.
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